Prevention or Termination of Pregnancy in Dogs and Cats : How to Prevent Dog Pregnancy After Mating
Estrus is the technical term for a female dog coming into heat. Also referred to as a season, it’s this small window when dogs are fertile and can become pregnant. Estrus is often accompanied by discharge and can be quite the hassle for normal pet families to deal with. While estrus is a naturally occurring phenomenon, prevention is beneficial to prevent unwanted pregnancy and to help avoid many complications from heat cycles such as temperament changes and pyometra, a potentially deadly infection of the uterus that occurs after a dog comes into season.
When does a female dog first come into heat?
Puberty, or sexual maturity, in the female dog usually occurs around six months of age. The smaller breeds tend to go into estrus, or “heat,” earlier, and some females can have their first “heat” cycle as early as four months of age. On the other hand, large and giant breed dogs can be up to two years old before they come into heat for the first time.
How often do female dogs come into heat?
On average, this occurs about twice a year, although it varies from dog to dog. When cycling first begins, there may be a great deal of variability in the time between cycles. This is normal. Some females take eighteen months to two years to develop a regular cycle.
Small breeds tend to cycle more frequently than the larger breeds. Three and occasionally four heat cycles per year can be normal in some females. Very large breeds may only cycle once every 12-18 months. In most giant breeds (Great Danes, Irish Wolfhounds, St. Bernard, etc.), an estrus cycle every twelve months is common.
How long does a heat cycle or estrus last?
Heat cycles vary but average two to three weeks for most dogs. The heat cycle begins with the first signs of vulvar swelling or vaginal discharge. It ends when all discharge ceases and the vulva has returned to its normal size.
How can I prevent my female dog from coming into heat and having puppies?
There are two methods to prevent estrus, or heat, in a female dog:
- Surgery – ovariohysterectomy (spay): Recommended.Ovariohysterectomy, or a spay surgery, involves the surgical removal of the entire female reproductive tract, including the uterus and both ovaries. It is a permanent and irreversible procedure. Although this is a major abdominal surgery involving general anesthesia, there is little risk associated with the procedure when it is performed by a veterinarian.
Recently, some veterinarians have begun to offer and recommend an ovariectomy; in this procedure, only the ovaries are removed, leaving the uterus. Ask your veterinarian what they recommend for your dog.
- Medical management using hormonal drugs: Not typically recommended,due to risks.
When a woman has a hysterectomy, the ovaries are not usually removed. Why is it necessary to remove the ovaries in my dog?
The reproductive cycle of the female dog is entirely different from that of woman. Female dogs come into “season,” or heat, twice a year on average, and it is only at that time that they can conceive. The purpose of an ovariohysterectomy is to ensure that the estrus cycle does not occur. This has numerous health advantages for the dog, including reducing the risk of breast cancer and eliminating the risk of ovarian and uterine cancer. In addition, unwanted litters are prevented and the behavioral changes associated with “heat” are avoided.
Are there any other advantages to spaying?
False pregnancy
Spaying your female dog will ensure that she does not experience the complications of false pregnancy. False pregnancies mimic true pregnancies and result in abnormal behaviors, as well as an increased risk of pyometra (uterine infection) and mastitis (mammary infection).
Pyometra
Pyometra refers to infection of the uterus. This is a serious and potentially life-threatening condition in un-spayed females, and the risk of pyometra increases with age. Spaying (ovariohysterectomy) eliminates the risk of this condition.
Breast cancer (mammary neoplasia)
Spaying a female dog prior to the first heat cycle reduces her risk of developing breast cancer to less than 0.5%, according to most experts. A female that goes through one heat cycle has an 8% chance of developing mammary cancer, and a dog that goes through two heat cycles has a 26% chance of developing mammary cancer. The earlier a female is spayed, the less risk she has of developing the number one form of cancer in dogs – breast cancer.
Medical control of estrus
There are currently no approved medications to control the heat cycle in dogs in the United States or Canada. In the European Union countries, there are some medications that are used to prevent pregnancy and regulate estrus. Some of these drugs have a high incidence of serious, even life-threatening side effects.
Causes and Prevention of Estrus
Estrus in female dogs occurs approximately every six months and is triggered by biological shifts in hormone levels that occur naturally in intact animals. While male dogs are fertile continuously once they reach sexual maturity, female dogs can only become pregnant during a narrow window during estrus. There are several available methods for preventing estrus
Canine Contraception
Much like in humans, there are various medications on the market that can prevent female dogs from coming in season. These contraceptives are typically administered via routine injections in your veterinarian’s office.
The drug of choice for contraceptive is called Delvosteron. Your dog will typically need an initial injection with follow ups in 3 months, then four months, then eventually every five months in order to prevent your female canine from coming into estrus. These shots will need to be continued throughout your dog’s life since her reproductive system works much differently than humans and your dog may still be able to become pregnant well into their senior years.
Canine contraception tends to have less of a systematic impact on hormone levels with fewer side effects than other treatment methods. Since your female dog’s uterus and reproductive system are still intact, she may be susceptible to infections and ailments such as cancer, prolapse or pyometra.
Spaying Your Dog
The most classic, well-tested and reliable method for preventing estrus in your dog is through spaying or fixing. In this procedure, your veterinarian will perform a surgical operation on your dog in which the entire reproductive tract is removed. This will require your pet to be placed under anesthesia and pre-surgical blood work will be needed. Veterinarians perform numerous spay surgeries every year and, once performed, will need little to no follow up care, other than the removal of stitches if dissolvable thread is not used. Spayed dogs will not experience estrus, pregnancy and have no reproductive organs left to be infected by various conditions.
Like most surgeries, spaying can involve some complications. Your pet should be in good overall health and your vet may perform pre-surgery bloodwork to ensure this is the case. Surgical incisions can become infected without proper at home care. You should always follow your veterinarian’s suggest post-op protocol in order to minimize these risks. Modern technologies such as the use of lasers during surgery can help minimize blood loss and promote quicker healing of incisions.
How to Prevent Dog Pregnancy After Mating
Few things pull on a human’s heartstrings like a litter of snuggly pups. Though undoubtedly adorable, with puppies comes big responsibility. Vet care, cleaning up after them, and feeding them can really cut into the family budget (and your free time). Breeding a dog is a lot of work and something most pet parents would prefer to prepare for. After all, caring for a pregnant and nursing dog, then adding 6 to 8 puppies (or more) to the mix, is a lot to take on. Not to mention that every pregnancy carries complication risks, even if the dog has a history of healthy births in the past.
Unfortunately, accidents do happen. In-heat dogs sneak out and link up with neighborhood dogs and often end up pregnant as a result. But there are some things you can do to prevent puppies after mating.
Spaying
When in heat, female dogs release pheromones to attract males, and males may travel considerable distances just to mate. Mating happens quickly, and the whole process can take as little as 10 minutes, often without pet parents even noticing it. Some parents don’t realize what has happened until their dog’s body starts changing. So what is a pet parent to do when they notice their pet’s tummy growing?
The first option to prevent puppies after mating is to spay the dog. Spaying is a minimally invasive surgery where a vet removes a dog’s uterus and ovaries. Vets can still perform the spay even if the dog is in early pregnancy, removing the fetuses along with the reproductive organs. Spaying during pregnancy carries a greater risk of surgical complications, is more invasive, and often costs more than a regular spay procedure. However, sterilization has a 100% efficacy rate and will ensure your dog never gets pregnant again.
Injections
Most dogs, given the opportunity, will end up mating when the female is in heat. A whopping 40% of female dogs will fall pregnant after just one mating session! That incredibly high number means you are at considerable risk of having a litter of unwanted puppies if you are not careful. Thankfully, there are relatively safe means to prevent pregnancy after mating.
One such option is known as a ‘mis-mating injection.’ If you suspect your dog mated in the last 22 days, then an injection of Alizin, an antiprogestagenic compound, may be an option. This medication will terminate the growing cluster of cells inside your dog and is 100% effective within 22 days of mating. It can also be administered later in the pregnancy, but it is less likely to be as effective.
Injections are an effective preventative measure to take, especially if given early. However, this is not a long-term solution, and it will not offer protection from pregnancy in the future. If you are looking for a long-term solution, we recommend spaying your dog.
Veterinary Abortion
Male dogs can be extremely persistent when it comes to female dogs in-heat, and they are not above breaking into kennels or digging under fences! Even responsible pet parents with big breeding plans can face unwanted pregnancies. If spaying and mis-mating injections are not an option, a veterinary abortion is a viable, effective way to terminate an unwanted pregnancy.
However, choosing to go through with an abortion is a big medical decision to make for your dog. Abortion carries more risks for complications than spaying or mis-mate injections. Most vets won’t perform them unless the dog is too far along for other options, and pregnancy is not feasible (either for health or personal reasons). Depending on how far along the dog is, vets may choose a surgical abortion or terminate pregnancy with abortifacient medications.
Abortions are tough on a dog’s body, and dogs often need to stay in the animal hospital for up to a week while they recover. Abortions are also expensive to perform, especially if the dog is late-term, and it won’t offer any protection against future unwanted pregnancies like spaying will.
Pregnancy prevention has many benefits for both pets and their pet parents. A litter of puppies is a tremendous responsibility. You’ll have to clean up their accidents, take them for their first vaccinations, deworm them, wean them, and keep them safe for at least the first 8 weeks of their life. Plus, you’ll still have to look after their nursing mother and find the puppies’ homes in the meantime.
Pregnancy can also put a lot of strain on a dog’s body, and some dogs may be at higher risk of pregnancy complications due to age, size, or breed. Plus, caring for a pregnant mother and her puppies is time-consuming and costly. Preventing pregnancy can spare your family from those financial burdens and extra work that comes with puppies and eliminate the risks of pregnancy-related health conditions in your pet.
Non-Surgical Contraception in Dogs and Cats
Medical control of reproductive cyclicity in dogs and cats can be achieved using a variety of different drugs. Gonadal steroids such as progestogens and androgens have historically been used for a long time, and their action will be reviewed here. A recent development is the use of long acting GnRH agonists.
Progestogens
Synthetic analogues of progesterone, also termed progestins or progestogens (PG), are pharmaceutical compounds commonly used to control the reproductive cycle of domestic animals The following PGs are commonly used in dogs and cats for temporary (starting the treatment shortly before proestrus onset) or prolonged (starting in anestrus) postponement of estrus, or for suppression of estrus (starting the treatment after proestrus onset) : medroxyprogesterone acetate (MPA), megestrol acetate (MA), proligestone (PR), chlormadinone acetate (CMA), delmadinone acetate (DMA), norethisterone acetate (NTA) and melengestrol acetate (MGA). From the clinical point of view all these product act in the same way through a block of the production and/or release of GnRH from the hypothalamus. These compounds show a variety of action on the reproductive and endocrine system (such as hyperplasia of the endometrium, hyperplasia of the mammary parenchyma, decreased production of adrenocorticosteroids, increased secretion of prolactin and growth hormone, insulin resistance) as well as some local skin reactions at the injection site and behavioral modification (increased appetite and weight, polydipsia, slight depression, decreased libido in males). In pregnant bitches and queens the use of PGs may cause masculinization of female fetuses if administered early in pregnancy (during organogenesis, up to day 25 after ovulation) or delayed parturition if administered in the last decade of pregnancy.
Clinical Considerations For a Safe Use of Progestogens
The above cited effects are not always present, are reversible and do not generally cause problems in healthy young to adult animals treated for not too long and using the recommended dosage. In general, a treatment period of 12 months is considered adequate in most individuals, although longer treatments can also be safe provided that the female is given a rest of a few months every year or so. While most bitches and queens may tolerate well treatment periods of more than 6 months, animals with a pre-existing disease such as subclinical diabetes, microscopic mammary lesion/tumor or cystic endometrial hyperplasia may see their condition worsen rapidly as a result of the PG treatment. The following is a series of considerations on patient selection and type of presenting complaint for which a PG treatment should or should not be used.
Do not use long acting compounds (such as MPA or PR or any other compound marketed for long term use) prior to puberty in felines, as this may cause the queen to develop a long-lasting mammary hypertrophy which could become a life-threatening situation. In prepuberal animals it is best to use initially a short acting compound (such as MA) per os for 1-2 weeks and then change to a long acting PG once potential side effects have been ruled out.
Do not treat pregnant females, as this may cause fetal developmental defects as well as delayed parturition, thereby causing fetal death in utero due to placental ageing and detachment.
Do not treat pseudopregnant bitches. During a PG treatment clinical signs of pseudopregnancy will disappear but will recur once treatment is discontinued, and the problem may worsen.
Do not treat a female during diestrus. The stage of the reproductive cycle should always be identified using vaginal cytology and/or serum progesterone assay, and the bitch or queen should best be treated during anestrus. Diestrus should be ruled out in felines too, as approximately 30% of queens ovulate spontaneously, maintaining thereafter a 30-45 day-long diestrus.
Do not treat females with uterine haemorrhage. Prolonged sanguineous vulvar discharge following parturition in the bitch can be a critical problem which should either be treated with a uterine contractive drug (i.e., as ergonovine) or sent to surgery. Milder bloody vulvar discharge can be caused by uterine neoplasia, cystic endometrial hyperplasia with superimposed endometrial inflammation, pyometra, metritis. None of these conditions will benefit from administration of a progestogen.
Do not treat diabetic patients. Although not always necessary, it would be wise to measure blood glucose before and/or after a prolonged treatment to confirm health status with regard to glucose metabolism.
Do not use PGs in females with prolonged heat. A prolonged heat may be due to ovarian cyst(s), a granulosa cell tumor, or may be due to a split heat (in the bitch) or to a misinterpretation of normal estrous signs by the owner. For none of these categories is a progestogen treatment indicated (although in some cases a young, health bitch with an ovarian cyst may temporarily benefit from administration of a progestogen). Therefore, bitches or queens with a prolonged heat should not be treated with a progestogen, unless a diagnosis of cystic ovarian disease has been carefully confirmed and surgery or administration of GnRH or hCG are not a valid therapeutic option.
Choosing the Right Candidate
The ideal candidate is an adult postpuberal female in anestrus. Before a female gets treated with long acting compounds she should be evaluated for normality of uterine and mammary conditions as well as of glucose metabolism. In fact, a long acting progestogen might precipitate a subclinical uterine, endocrine or mammary condition (such as diabetes, cystic endometrial hyperplasia-pyometra in the bitch or mammary hyperplasia in the queen) which often are not clinically evident in the early stages, and which have been reported (albeit rarely) also in young animals. If one of the above conditions is present the administration of a long acting progestogen prior to diagnosis may pose a serious health threat on the female. A minimum database of clinical information to be gathered prior to administering a long-acting compound should include:
Collecting a thorough reproductive history to rule out occurrence of estrus within the last 1-2 months (which would mean that the female is in diestrus)
A complete clinical exam
Palpation of the mammary gland to rule out presence of mammary nodules
A vaginal smear to rule out presence of oestrus
Table 1 shows the suggested dosages of the most commonly used progestogen-based compounds in the bitch and queen.
Table 1. Suggested dosages of the 3 most commonly used progestogen compounds in bitches and queen for the control of estrous.
| Suggested dosage | Dog | Cat |
| Medroxy-progesterone acetate | 2.5-3.0 mg/kg IM every 5 months | 2.0 mg/kg IM every 5 months |
| Megestrol acetate | <2.0 mg/kg administered for <2 weeks in proestrus, or <2.0 mg/kg administered for a longer duration of time in anestrus. A typical dosage for estrus suppression is 2.0 mg/kg/day for 8 consecutive days, while a typical dosage for temporary postponement is 0.5 mg/kg/day in late anestrus. | In anestrus: 5 mg/cat every 2 weeks or 2.5 mg/cat/week (better if divided into 2 administrations every 3.5 days) in proestrus: 5 mg/cat/day for 4 days, then 5 mg every 2 weeks. |
| Proligestone | 10-33 mg/kg SC every 3,4,5,5 months | 10 mg/kg SC every 3,4,5,5, months |
Androgens
Androgens are also widely used for the control of estrous cycle in dogs and cats, although less information is available on most of the active principles commercially available for veterinary use. In the male, androgens cause a block of spermatogenesis (due to degeneration of seminiferous tubular epithelium), an increase in libido, a higher incidence of priapism, and growth of prostatic tumors. In the female, the main reproductive effect of androgens is to cause suppression of ovarian activity thanks to a negative feedback on the pituitary which decreases gonadotropin secretion; the ovaries of dogs treated with an androgen generally contain primary and secondary follicles but few that mature to ovulatory size. Androgens will also cause atrophy of mammary gland/endometrium and lactation arrest.
Mibolerone (originally marketed by Upjohn as Cheque drops®) was until recently the only androgen approved for estrus suppression in bitches in the United States. Other androgens marketed in Europe for human or veterinary use such as testosterone, methyltestosterone nandrolone and stanozolol are sometimes used in bitches, although recommended dosages are not available for each one of these compounds. Androgens are not recommended for use in breeding animals. Estrus suppression can be achieved starting the treatment at least 30 days before onset of the next proestrus and for as long as estrus suppression is desired. Prolonged postponement can be achieved in bitches for up to 2-5 years. Return to estrus averages about 70 days, with a range of 7 to 200 days. There are no published reports describing fertility after treatment with androgens. Although most bitches seem to exhibit apparently normal fertility, we have occasionally observed cases of prolonged anestrus in bitches treated with androgens. The most commonly reported side-effect of androgens in female dogs is clitoral hypertrophy, which occurs to some degree in 15 to 20% of dogs treated with mibolerone. Other reported side-effects of androgens include creamy vaginal discharge, vaginitis, increased mounting and aggressive behaviour, anal gland inspissations, musky body odor, obesity, and epiphora. Androgens are contraindicated in potentially pregnant bitches, as they may cause masculinization of female fetuses; in prepuberal bitches, in which they may precipitate premature physeal closure, and in dogs with renal or hepatic diseases (Olson et al., 1986a). Presence of intranuclear hyaline bodies in hepatic cells and, rarely, changes in liver function tests have been described in dogs after treatment with mibolerone; clinical significance of hepatocellular changes is unknown. Testosterone also has been described for estrus suppression in bitches. Successful regimens reported include injection of 100 mg testosterone proprionate once weekly, oral treatment with 25 to 50 mg methyl-testosterone twice weekly, and subcutaneous implantation of at least 759 μg/kg. Testosterone, methyltestosterone and nandrolone are currently used with indications such as oestrus suppression, false pregnancy, lack of libido as well as with other non-reproductive indications (renal insufficiency, anemia, post-surgery etc.). Testosterone propionate (100 mg once weekly) and methyltestosterone (25-50 mg twice weekly per os) are currently marketed in some European countries for oestrus suppression. Canine false pregnancy can safely be treated with androgens as it does not recur following cessation of treatment unlike what happens with progestins.
Long-Acting GnRH Agonists
A recent development in the field of the control of reproduction in the bitch is the use of long-acting GnRH agonists such as deslorelin, which have become commercially available as veterinary drugs in Europe during 2008. In a recent study (Romagnoli et al., 2009) to evaluate clinical efficacy of deslorelin for inhibiting reproduction in the bitch, 10 adult, healthy bitches or bitches with mammary neoplasia for which owners were requesting suppression of cyclicity without performing gonadectomy were administered a 4.7 mg or a 9.4 mg deslorelin implant subcutaneously. The study design included history, physical exam, uterine ultrasound, haematology, serum biochemistry and progesterone (P4) assay to be performed prior to treatment, with physical exam and serum P4 to be repeated every 2.5 months until the treatment was discontinued. The first implant of deslorelin was administered in anestrus (N=5) or in diestrus (N=5).Treatment was repeated every 5 months for as long as necessary based on the clinical situation of the dog and owner’s desires. Some of the bitches implanted in anestrus came in heat within 4-15 days after treatment, while none of the bitches implanted in diestrus showed heat during treatment. Suppression of reproductive cyclicity was successfully achieved in 6/10 bitches for 1-4 years. No behavioural and local/general side effect were observed in any of the treated bitches. The 4.7 mg deslorelin implant may work well for suppression of cyclicity provided that it is administered in diestrus and at intervals of 4.5 months. The 9.4 mg implant may be more suitable for this use although its efficacy may also be shorter than 12 months. Owner compliance is an important limiting factor.
GnRH agonists can be used to control reproduction also in male dogs as well as in male and female cats (Romagnoli et al., 2005). We have administered the 4.7 mg deslorelin implant to adult dogs and adult and prepubertal male and female cats. Adult dogs respond well to the treatment, and we have observed a sharp reduction of fertility and aggressiveness in all (4/4) treated dogs, while libido has not always been affected completely in these animals as they were adults and well trained in breeding bitches in heat (Romagnoli, unpublished data). Results in male cats have been less reliable, with some animal responding well (loss of penile spikes, loss of libido, loss of aggressiveness) while others have kept showing good (albeit decreased) libido, good fertility and unchanged aggressiveness. Based on our ongoing studies in adult queens, the 4.7 mg deslorelin implant seems to be effective in inhibiting reproductive cyclicity for >12 months, and good efficacy has also been observed in delaying puberty in male and female cats implanted at 2-4 months of age (Romagnoli, unpublished data).
Contraception in Dogs and Cats
Nonsurgical contraceptive measures include permanent or temporary pharmaco-castration of males, reversible and nonreversible estrus prevention in females, estrus suppression in females, and pregnancy prevention or termination after unwanted mating. As for females, no new products for estrus prevention or suppression have been introduced in the last decade, other than revised formulations and new brands of progestins previously marketed. In fact, contraceptive options in bitches have decreased in some countries with the recent withdrawal of the androgen mibolerone (Cheque Drops©) as an estrus preventative. However, an implant product providing down-regulating amounts of a potent GnRH-agonist has recently been approved as male dog contraception in New Zealand and Australia, and efforts are underway to obtain approval as a contraceptive in bitches as well, as well as application to cats. Depending on price and regulatory hurdles, the product is likely to become available in many countries in the next decade. There are significant advances in protocols and products available for termination of unwanted pregnancies, including extra-label uses of prostaglandin, of PG analogs, of dopamine agonists, and of dexamethasone in selected situations; additionally, the anti-progestin aglepristone is approved and sold with an indication of pregnancy termination in some countries. The goal of non-surgical contraception in males has advanced on two fronts: the above-mentioned GnRH-agonist implant technology, and a new product that provides testis-necrosing doses of a metallic salt injected directly into the testes.
PROGESTINS
Progestin administration remains the widest available method of cycle prevention in dogs. They are marketed with an indication for use in female dogs, and in some countries there may be an indication or suggested doses for use in cats. In all cases, progestin administration is intended to produce an artificial luteal phase (i.e., circulating progestin mimicking the normal post-estrus profile of progesterone); during this period a new ovarian cycle will not occur and following it a normal anestrus period is reinitiated. The progestin acts at the hypothalamic-pituitary level, primarily preventing increases in GnRH (and thus gonadotrophin) secretion that would otherwise occur as the stimulus for the next follicular phase and proestrus. Oral formulations are given daily; depot-injectable formulations, by single injections; extended therapy in either instance is by repeating the treatment at 2-5 month intervals, based on manufacturers recommendations. Generic progestin formulations marketed under various brand names in different countries include oral megestrol acetate, depot-injectable medroxy-progesterone acetate (MPA), oral MPA, depot-injectable proligestone, and others. The number of trade names under which each is marketed is large and expanding as these compounds go off patent and are produced as new brand names of the generic drug, often with the progestin identified only by a chemical name that is not typically used but is scientifically synonymous with the more commonly used chemical or generic name. MPA can validly be identified by any one 16 synonymous chemical formulas (e.g., 6-alpha-methyl-4-pregnene-3, 20-dion-17-alphaol acetate; 17-alpha-Acetoxy-6-alphamethylpregn-4-ene-3,20-dione) and an additional 14 generic drug names (e.g., MPA, mespirenone, NSC-26386, farlutin), in addition to 12 or more product brand names (e.g., Promone, Depo-promone, Perlutex, Repromap, Supprestal, Gestovex, etc). The situation is just as complex with megestrol acetate, as it has over 40 different chemical, generic, and trade names, and the number of brand names continues to increase as generic drug companies produce their own brands of same formulations. Unfortunately, doses and treatment protocols vary among manufactures, often markedly and incorrectly, and caution should be exercised because of the modest margin of safety as regards known side effects.
Side effects
There is likely no universally safe and effective dose of any of the progestins in either dogs or cats. In both species, effective dose can in some individuals result in uterine disease or diabetic-like symptoms. In dogs, reported possible side effects seen with recommended doses but more often with higher than recommended doses include mammary hyperplasia and mammary tumors, elevated Growth hormone and acromegalic changes, diabetes, adrenocortical suppression, masculinization of female fetuses, local skin reactions, and behavior changes including increased appetite with weight gain. Nevertheless, many bitches tolerate recommended doses well, without side effects. Of primary concern is the potential to cause cystic endometrial hyperplasia and resulting pyometra, especially if the dose is excessive and/or administered in late proestrus, estrus or the luteal phase, where interaction with a prior elevation in estrogen can magnify potential effects on the uterus. Administration in dogs should be limited to confirmed anestrus or very early proestrus. The latter should be confirmed by vaginal cytology as owners often recognize proestrus too late for safe or even effective administration. Administration late in proestrus can result in induction of a fertile ovulation rather than suppress the impending ovulation. In cats, spontaneous ovulations can occur, and the hormonal and cycle status of the queen should be confirmed before initiation of treatment. Contra-indications include pregnancy, and any history of reproductive tract, mammary or liver disease.
Megestrol acetate
In North America the only drug so marketed is Ovaban, 5 and 20 mg tablets, by prescription only, for use in dogs only, not more than successive cycles of use, not before or during first estrus cycle (i.e., pubertal proestrus), for postponement of estrus; administration in anestrus, at 0.25 mg/lb body weight per day for 32 days administered orally, intact, or crushed and mixed with food; administration in proestrus at 1 mg/lb per day for 8 days-administered orally, intact, or crushed and mixed with food. There is no indication for use in cats. The nearly-or quasi-equivalent metric doses and protocols for dogs, and those usually but not always recommended in European products are, for anestrus, 0.5 mg/kg/day for 32 days or 40 days, and for proestrus, 2.0 mg/kg/day for 8 consecutive days. In some countries there are products with an indication for use in prepubertal bitches and during pubertal proestrus; likewise, there may be indications for use in cats at doses of 5 mg/cat every 2 weeks or 2.5 mg/cat per week, or 5 mg/cat/ day for 4 days, then 5 mg once every 2 weeks It has been suggested that dosing in cats, as in dogs, if considered, should incorporate a dose per unit body weight, such as 0.5-1 mg/kg or less, assuming previously recommended dose would be sufficient for 5 kg or larger cats; dosing by body weight might limit the occurrence of side effect sin smaller cats. Dose response studies for cats have not been published. Where oral MPA is marketed, there are similar anestrus and proestrus protocols, with recommended doses that have not been subjected to dose-response studies that have been published.
Depot-MPA
Greater caution should be exercised with depot injectable progestins, as the treatment cannot be quickly discontinued in the event of overdosing or idiosyncratic occurrences of side effects. Conservative does are on the order of 2.5-3 mg/kg every 5-6 mos. in dogs, and 2-mg/kg/5 mo. in cats. Animals should be monitored for potentially debilitating side effects. Anecdotal reports suggest that experiences with proligestone are not very different from those with MPA, including the potential for undesirable reproductive and metabolic side effects. The typical product, i.e., Covina© or Delvosteron© Intervet 100 mg/ml is recommended by the manufacturer to be administered at doses of 10 to 33 mg/kg, given to bitches at 0, 3 and 7 months of treatment, and subsequently at 5-month intervals.
Progestin implants
In zoo-maintained exotic carnivores silastic implants of melengestrol acetate were used for many years but resulting uterine disease has reduced interest in their use. In dogs and cats, implants of progesterone, androgen and synthetic progestins have been shown capable of providing cessation of cycles, but studies of safety have been limited. One concern is whether the implants can provide steady state release with first order kinetics as opposed to burst release in the initial weeks. Implants of levo-norgestrel (Norplant) marketed for human sue, as well as equivalent implants made with generic levonorgestrel have been show to have a contraceptive efficacy in female cats but not dogs at doses that were multiples of the human dose on a body weight basis. Recently, silastic implants of a new design and containing a synthetic progestin have been reported to have first-order release kinetics when placed subcutaneous in dogs or cats and to provide safe and effective estrus cycle prevention for at least 2 years, without side effects. (Verstegen et al., 2004; Verstegen, personal communication).
ANDROGENS
Mibolerone is no longer marketed in the U.S. Performing dogs and working dogs are often subjected to high doses of synthetic androgens or testosterone esters are a mode of contraception, notwithstanding the potential anabolic effects that may accompany treatment. Clinicians should be aware of such drug abuse in dealing with animals with signs of masculinization, elevate hematocrits, adrenal suppression, and persistent anestrus.
GNRH AGONISTS
Available data suggest that 3 and possibly 4 different GnRH agonists have been shown to suppress gonadal activity in both male and female doges, to have a high margin of safety, to be fully reversible whether administered in adults or beginning prior puberty. The drugs are all decapeptides that represent modifications of the natural GnRH via substitution of one or more natural or synthetic amino acids resulting in potencies 100-200x that of GnRH. Formulation and marking of a commercial product involves or will involve implants to be placed s.c. via a needle/trochar, and which will release effective systemic concentrations for 6 mo. to one year or more. The agonists, when administered continuously, act by causing a protracted down-regulation of the GnRH receptors on gonadotrophin-secreting cells of the pituitary, following a brief period of up-regulation that causes a transient increase in LH and FSH (an effect sufficient to induce estrus in anestrus bitches). The resulting chronic suppression of LH and FSH concentrators results in suppression of gonadal hormone secretion and gametogenesis–a chemo-castration effect in males and a protracted anestrus in females, in each case reversible. Peptic, Australia has gained approval of sale of its implants of the GnRH analog deslorelin analog by the relevant authorities in Australia and New Zealand under the name Suprelorin©. The registered product claims efficacy for at least 6 months in 98% of male dogs as contraception, and use a treatment for benign prostatic hyperplasia (BPH) and as and as an aid in the control of unacceptable behavior. The expectation is to produce an implant with an efficacy per implant that last for one year, and to gain approval for the product being indicated for use as a cycle-preventing contraceptive in female dogs.
One caveat in using GnRH agonists in females is the concern of inducing a fertile estrus at the start of the treatment period, which is a typical response unless the animals are less than 3-5 months of age or have elevated progesterone concentrations (i.e., are within 1 month of a prior estrus or are pretreated with a progestin). Intervet researchers have reported on a formulation of an GnRH-agonist that is a modification of the human drug nafarelin, and the azaglynafarelin is formulated in a controlled release device, Gonazon-CR©. It safely and efficiently prevented puberty in female dogs throughout the treatment period of 1 year beginning at 4-5 months of age. Prevention of puberty did not appear to affect body weight or growth compared to controls in the study. The potential for this product to also come to the veterinary market also seems very promising.
TESTIS-NECROSING INJECTIONS
In the U.S. the FDA has approved the product Neutersol© (Addison Biological Laboratories) developed by Technology Transfer, Inc. The injectable solution contains 13.1 mg/ml zinc as zinc gluconate that is neutralized to pH 7.0 with L-arginine. The indication is for intra-testicular injection to produce sterilization in 3-10 month old male dogs, the volume injected into each testicle being based on testicular width as determined by measuring each testicle at its widest point using a metric caliper. More than 99.5% of animals studied became sterile, but testosterone levels we only reduced by approximately 50%. Marketing is to both private practices and to animal welfare faculties with an interest in reducing the per overpopulation problem in the U.S. The claim is that by using fine needle injections, the procedure is tolerated by dogs without sedation, and that the side effects are usually minor. Local reactions included the expected testicular swelling, and in some cases pain with biting and licking at the scrotum, swelling of the prepuce and irritation, ulceration, and/or infection of the scrotum. Systemic reactions included an increase in the white blood cell count, vomiting, anorexia, lethargy and diarrhea. Withdrawal of food for 12 h pre injection is suggested. Scrotal swelling without pain may persist for a few months.
CURRENT RESEARCH: NEW MODES OF CONTRACEPTION
These include reports of several promising approaches intended to interfere with GnRH action, with function of pituitary gonadotrope cells responsible for secretion of LH and FSH, or with the action of LH on the ovary. Such approaches include presentation of GnRH or GnRH-like peptide multimers and/or protein conjugates as vaccines in protocols using new and more readily acceptable, less irritating adjuvants; delivery of a GnRH-vaccine expressed by modified virus; administrations of GnRH-peptides with GnRH or GnRH-agonist linked to a cytotoxin and/or membrane-active lytic peptide, intended to result in gonadotrope cell uptake of the cytotoxin and cell destruction; and use of a vaccine for immunization against bovine LH-receptor presented via silastic implants and serial booster injections, intended to prevent ovarian cells from responding properly to endogenous LH. Additional vaccine approaches include myriad proposed methods for immunization against the peri-oocyte zona pellucida proteins, especially ZP3, using as immunogen either a purified ZP protein or crude ZP preparation with one of many proposed acceptable but potentially sufficiently effective adjuvant or carrier system,
PREGNANCY TERMINATION AND PREVENTION: EXTRA-LABEL DRUG USE
Many of the protocols involve the extra label use of drugs marketed for use in other species, or for other indication in small animals, ideally along with ultrasound to confirm efficacy. These include natural prostaglandin F2a (PGF) at doses of 20-100 ug/kg, i.m. or sac., at a minimum of 2 times per day, to effect, and, various PGF-analogs marketed for use in large animals (e.g., Cloprostenol injections every 2 days, to effect), given after confirmation of pregnancy in dogs. Higher doses required in cats have been less well studied. Likewise, dopamine agonists including cabergoline marketed in some countries for suppression of lactation; given orally daily after day 30 (and to effect) in prolactin-suppressing doses will cause luteolysis and terminate pregnancy. In dogs, immunosuppressive oral doses of dexamethasone () given for 10 days will terminate pregnancy probably by mimicking mechanisms similar to those that occur naturally at parturition, and may be justified in certain locales and circumstances; the induced adrenal suppression is reversed immediately upon withdrawal. Recently, combination therapies of PGF or PGF-analog in conjunction with a dopamine agonist (cabergoline or bromocriptine) were show to have high efficacy and the potential to utilize lower amounts of the drugs and minimize side effect. These protocols have been reviewed in detail (Wanke et al, 2002, www.ivis.org).
ANTI-PROGESTIN: AGLEPRISTONE
The progesterone receptor antagonist aglepristone is currently marketed in a limited number of countries in Europe and South America, e.g., Alazine ©, Virbac France, 30 mg/ml, with an indication for termination of pregnancy any time after mating. Doses of 10 mg/kg administered twice, with an interval of 24 h, have been reported to terminate pregnancy given en at day 15, 30 or 34 of pregnancy. The protocol and findings have been reviewed in detail (Fieni et al, 2001, www.ivis.org)
Prevention of Unwanted Pregnancies in Dogs
Preventing unwanted pregnancy in dogs is a lot easier than having to terminate it later. You will be putting your dog through emotional, physical, and mental distress and in turn playing with her long-term health.
Pregnancy termination in dogs is legal. It can be done through a surgical spay or a drug-induced abortion depending on the stage the female dog is at in her pregnancy.
Here’s how you can prevent an undesired and unintended dog pregnancy.
Spaying & Neutering
Spaying refers to an operative surgery that sterilizes female dogs. Neutering refers to the operative surgery that sterilizes male dogs.
With females, it involves removing the fallopian tube, both the ovaries and the uterus. Spaying is a crucial surgery but your precious female will bounce back to normal within two weeks. Once the stitches come out, she’ll be even better than she was before.
Sterilizing dogs has many benefits. If you’re not intending to mate your dog ever—it really is the best thing you can do for her. It reduces the chances of a lot of illnesses and infections in your dog. Not only that, but you’ll also have peace of mind, knowing that she won’t attract any male dogs to mate.
Female dogs never go into menopause. So spaying them will save you a lifetime of discharge and odors while keeping her happy and safe as well. But above all, spaying is a safer and painless solution as opposed to aborting an unwanted dog pregnancy.
Enclosures and Kennels
Dog enclosures, pet playpens, and kennels are the second best and safest ways to prevent an unwanted dog pregnancy. Choose these if you are not looking at sterilizing your dog and are maybe looking at having a litter in the future.
A female dog goes into heat every 6-8 months, depending on her cycle. If you’re not looking to breed her during a particular cycle, keep her confined indoors. Either put your dog in an enclosure or kennel or keep her inside the house. Although the latter option can be a tad uncomfortable since dogs in heat can be somewhat messy.
Some companies make special pet containment units for dogs in heat. But the regular ones work just fine too. You need to have an area where other dogs can’t enter at all. Keep the enclosure on a concrete or tiled surface so that it is easier to clean and harder for male dogs to dig into. Seal it against trespassing by other dogs, in every possible way.
Panties and Diapers
Fail-proof, cheap, and clean—panties and diapers for dogs in heat are great when you have to keep your dog indoors. The period or the heat in a dog lasts for about 3 weeks. So these work great and prevent blood drips for messing up your carpet.
Dog diapers not only contain the discharge, but they also curb a lot of the odor, which minimizes the scent for dogs in the vicinity. Even if the male dogs come looking for her, you can keep put your dog indoors until the end of her estrus. And rest assured, thanks to these sanitary pads or diapers for dogs, you won’t be cleaning up after her.
Termination
Usually, a dog’s pregnancy should be terminated within 45 days of gestation. After this, it can be very dangerous for the dog’s mental and physical health. Trying to abort a dog pregnancy after the stipulated time frame results in the birth of dead puppies, which can be very traumatizing for the mother.
To ensure that the abortion takes place in time, look out for telltale signs like enlargement of nipples, weight around the abdomen, and morning sickness. Get a scan done from a vet to be sure.
Having said that, terminating an unwanted pregnancy in dogs is just as painful and traumatic for the female dog as it is for humans. It can take its toll emotionally and mentally and leave her in distress. Whether it lasts for a few days or months, it depends on the dog.
Ethically, it is just as controversial, if not more (because you’re literally deciding for the dog), to terminate a fetus. So try and prevent it at first.
We know that accidents do happen, so here are some known methods to induce abortion in pregnant dogs. These require you to know of a female dog’s pregnancy as soon as possible.
Oral Estrogens
These are not recommended for dogs and should be your absolute last case option. Oral estrogens are the “morning-after pill” for dogs and are not the preferred choice for carrying out a healthy abortion.
Estrogens are known to cause diseases and infections like pyometra or infected uterus. This can turn fatal before you know it. They are also ineffective if not administered at the right time. So you’re putting your dog’s life at risk for nothing.
Mismate injection and Misalliance Treatment
A drug called Alizin is injected into the neck. Two injections need to be administered 24 hours apart. In order to terminate an unwanted dog pregnancy. This is called Mismate or Misalliance treatment, referring to mating that should not have taken place.
The drug blocks the progesterone receptors in a dog’s uterus, subsequently disabling the uterus to maintain the pregnancy. This causes an abortion. It is highly effective when given within 22 days of gestation.
Speak to your vet before giving your dog this injection and responsibly supervise your pet after administering the treatment. You can expect discomfort and side effects for some time after the treatment, and if it persists, you must seek medical help.
Injectable Estrogens
Injectable estrogens are a lot safer, compared to the oral ones. The only catch is that they must be administered to the dog shortly after mating.
Injectable estrogen is the best solution when you catch the dogs in action or right after the copulation has taken place. That is when they’re most effective in preventing pregnancy. They also allow the female dog to get pregnant later on if you do wish to breed them responsibly.
Here-below are the two most used injectable hormones.
Prostaglandin F2 Alpha
With minimal to mild side effects and high success rates, Prostaglandin F2 Alpha is a preferred drug to abort dog pregnancies. It’s a completely natural hormone and is safe to use. However, a trained professional must administer it to the dog and the animal must be kept under observance.
Usual side effects include trembling, nausea, and diarrhea, sometimes panting and shortness of breath may also occur. A vet must be present to keep these under control.
The hormone is known to cause luteolysis, which induces termination of pregnancy in dogs and other animals. It is also known to cause contractions, thus resulting in abortion.
Dexamethasone
Dexamethasone is an immunosuppressant steroid, which is used in both humans and animals to treat a lot of disorders. In dogs, this drug is prescribed for diseases of the eyes and skin.
Administering dexamethasone under strict medical supervision can result in non-complicated and relatively painless abortions in dogs. Depending on how the animal reacts, the fetus is either eliminated or absorbed by the dog’s body.
Some of the side effects of taking dexamethasone to abort dog fetuses are mild to severe, but these side effects are really rare and hardly fatal. Some dogs may experience vaginal discharge and anorexia too.
The drug should be injected into the dog’s system within a few days of copulation, even better still if it is administered within a few hours.
Dopamine Agonists
Dopamine agonists work in terminating dog pregnancies by suppressing the production of prolactin—a hormone that is crucial for maintaining pregnancy. Quelling prolactin directly results in decreased progesterone, thereby aborting the pregnancy in dogs.
The reason this is a popular method of terminating unwanted pregnancy in dogs is that it is a safe and effective method, with little to no side effects. The major side effects of taking this drug are a loss of appetite and nausea in dogs.
The good thing about dopamine agonists is that they need to be administered after 25 days of gestation, giving enough time to think the abortion over and for the pregnancy signs to show.
Epostane
This drug works by not letting the body produce progesterone. The lack of progesterone automatically terminates the pregnancy within seven days.
No side effects have been reported post administering epostane, making it a fail-safe and fool-proof method to abort dog pregnancies.
Unwanted Canine Pregnancies – FAQ
Unwanted canine pregnancies are a massive source of worries in most dog owners, and even breeders. While most dog owners never go through one, it can be taken as a disaster when it happens to your female dog.
Here are some common questions answered about unwanted dog pregnancies!
Relaxin is the hormone that is measured by canine pregnancy tests.
Until when do you have, to terminate an unwanted pregnancy?
Unwanted pregnancies should usually be terminated within 45 days of gestation.
The signs of pregnancy will begin to show in your dog within a few days—look out for physical and behavioral symptoms. If you’re in doubt of whether your dog is pregnant or not, a simple scan will determine it.
Fetal signs of pregnancy in dogs can show up only after 25 days of gestation in the scan, after which you have about a week to decide what you want to do.
Typically, abortion and termination of pregnancies in dogs through medicines requires a week’s worth of medication. So be on the safe side and determine your dog’s pregnancy early in the day.
Can you abort a pregnant dog at home?
Aborting your dog at home isn’t safe and is definitely not advised. Always involve your vet in the process and conduct the termination of the pregnancy under careful supervision.
While home remedies may work, they can have also a plethora of side effects, which can harm your dog. Instead, opt for safe and medically approved methods to terminate your dog’s unwanted pregnancy.
The termination procedure usually lasts for a week to ten days, during the course of which also, you need to keep your pet under a vet’s keen eye. So conducting a home procedure without any supervision is nothing less than dangerous and careless.
What are the risks of stopping an unwanted pregnancy?
A lot of the risks depend on how, when, and in what manner are you aborting the pregnancy in your dog.
When done with the help of safe drugs, under a veterinary doctor’s guidance and supervision, and within 25-30 days of gestation, the abortion poses little to no risks.
Side effects of certain drugs may range from nausea to loss of appetite and lethargy. Sometimes, dogs may also show symptoms like vaginal discharge, bleeding, and behavioral changes.
Most drugs will render a dog capable of procreating in the future, but sometimes when the pregnancy is terminated at a later stage, the dog may give birth to dead puppies. This can affect her emotionally. This can affect children in your household, too.
If proper care isn’t taken, after the abortion, the dog will be prone to uterine infections.
Is there a morning after pill for dogs?
Yes, there are certain pills that work as morning-after pills for dogs. These are administered within a few hours of copulation.
Morning-after pills for dogs are extremely ineffective and are known to cause serious infections in dogs. Most commonly, they cause pyometra or infection of the uterus. These infections, if not taken care of, can turn fatal.
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development) Image-Courtesy-Google Reference-On Request.
