Clinical Use of GnRH Agonists in Canine and Feline Species

Reversible Contraception in Males: An Obtainable Target?

The last few decades have brought contraception to the forefront of research, with great strides made in effectively targeting and optimizing the physiology, pharmacology, and delivery processes that prevent pregnancy. However, these advances still predominantly target female contraceptives for the prevention of contraception, whereas targeting the male sex has lagged far behind. This has led to a marked deficiency in safe and effective male contraceptive agents, resulting in a heavy dependence on female contraceptives to prevent unwanted and unplanned pregnancies. Current research in the veterinary field and in rodents highlights several promising avenues whereby novel, safe, and effective male contraceptive alternatives are being developed-with an emphasis on reduced side effects and reversibility potential. This review aims to discuss current and novel male contraceptives (both human and veterinary formulations) while highlighting their efficacy, advantages, and disadvantages.

Efficacy and Safety of 4.7 mg Deslorelin Acetate Implants as a Neutering Option in Male Cats: A Large-Scale Multicentre Randomised Controlled Study

This multicenter-controlled, double-masked randomized European study was conduc-ted to confirm both the efficacy and safety of a deslorelin implant in controlling fertility and sexual behavior in a large population of tom cats over a 12-month period. Among the 225 screened individuals, a total of 205 privately owned indoor intact male cats, aged 3 months of age or older, were randomly allocated to a deslorelin implant (n = 154) or to a negative control group (n = 51). After the screening visit performed between day (D)-14 and D-7, six additional visits were sche-duled on D0, D45, D93, D186, D279 and D372. Effects on testosterone, sexual behaviors, penile spines, testicular volume and intact male cat urine odor were assessed at every visit under masked conditions as regards to the treatment group. In addition, phone calls from the investigators to the owners were scheduled on D7 and then on a monthly basis whenever no visit was scheduled. Success was defined as an individual serum testosterone concentration below or equal to 0.10 ng/mL and was 77.9% at D45, 83.1% at D93, 84.4% at D186 and D279, and 61.7% at D372 in the deslorelin group, and 3.9% at D45, 5.9% at D93, 3.9% at D186, 7.8% at D279 and 3.9% at D372 in the negative control group. Testing for superiority was made stepwise from D45 to D372 upwards; the difference in success rates was significant from D45 to D372 (p < 0.001 for each time point). The mean testosterone concentration dropped from baseline in the deslorelin group, remaining below the set threshold of 0.1 ng/mL until D372. From D7 onwards, the mean sum score for sexual behaviors (including vocalization, urine marking, aggression and intact male cat urine odor) was significantly lower at each observation time point in the deslorelin group compared to the control group, where no decrease in scores was observed. The mean percent change to baseline of the testicular volume and the percentage of cats with a decreased visibility and adult appearance of penile spines were significantly lower in the deslorelin group as soon as D45. No relevant safety concerns were reported during the course of the study. The deslorelin implant Suprelorin^® 4.7 mg (Virbac, Carros, France) is a safe and effective neutering option, inducing infertility over a 12-month period when administered to intact male cats aged between 3 months of age and 11 years of age. The implants also successfully reduced sexual behaviors (i.e., vocalization, urine marking, aggression), intact male cat urine odor, testicular volume and penile spine score for 1 year (372 ± 5 days).

Serum Anti-Müllerian Hormone Levels and Estrous Monitoring of GnRH Agonist Deslorelin-Induced Estrus in Bitches: A Pilot Study

This study was performed to monitor estrous patterns and, more importantly, changes in anti-Müllerian hormone (AMH) concentrations during the peri-ovulatory period in deslorelin-induced estrous bitches. Healthy anestrous bitches (n = 4) were used. Estrus and ovulation were monitored after deslorelin implantation. Blood samples were collected for analysis of progesterone, estradiol-17ß and AMH concentrations before implantation (day 0) and on days 6, 8, 10, 12, 14, 16, 18, 20 and 22 after implantation. Six days following treatment, all bitches showed estrus signs. Ovulation took place between days 12 and 15. Circulating AMH concentrations varied among bitches from 0.12 to 3.08 ng/mL. However, no significant differences in AMH levels (mean ± SD) were observed between day 0 and days following post-implantation (p > 0.05). There were no significant correlations between AMH and estradiol or AMH and progesterone (p > 0.05). Ultrasonographically, the number of clearly identifiable ovarian follicles was higher before ovulation and the area of ovaries increased after ovulation (p < 0.05). Except for AMH, changes in vaginal cytology, estradiol-17ß and progesterone levels observed in our study were similar to naturally occurring estrus. Large intra- and inter-individual variation in AMH were observed suggesting that AMH is currently not suitable as a canine fertility marker to monitor ovarian response to deslorelin treatment for estrus induction.

Chronic Use of Deslorelin in Dogs: Six Cases (2005-2022)

Deslorelin is currently registered for the induction of temporary infertility in male dogs, male cats, male ferrets, and also prepubertal female dogs, but research has shown its usefulness for other conditions requiring chronic treatment. This paper presents six cases of dogs chronically treated with deslorelin for indications such as benign prostatic hyperplasia, control of fertility, abnormal reproductive behavior and urinary incontinence. All animals were in good health during treatment. Treatment duration was 2-9 years. No short-term side effects were observed except for flare-up reactions, which were observed only in 1/4 intact males. Two dogs developed a neoplasia: a spayed bitch treated for urinary incontinence developed a pituitary carcinoma, and an intact male dog implanted for control of fertility developed a bladder carcinoma. While the pituitary carcinoma seems unlikely to be related to deslorelin, the bladder carcinoma could be due to the neutered condition of the dog (which was treated for 9 years) as urinary tract neoplasia is more common in dogs following gonadectomy. Chronic treatment with deslorelin is regarded as safe when an animal is being treated for life. The possibility that a pause in the treatment might be helpful for the animal should be investigated.

Reversible Control of Reproduction In Queens: Mastering the use of reproductive drugs to manipulate cyclicity

BACKGROUND

The literature is full of papers reporting side effects of progestogens in cats; however, they are, in fact, safe drugs, as discussed in this article. Gonadotropin-releasing hormone (GnRH) agonists and melatonin are additionally a practical solution for controlling cyclicity in queens, but they also have some contraindications and need to be used carefully.

CLINICAL RELEVANCE

Mastering the use of reproductive drugs allows feline practitioners to handle many more clinical situations than can be solved using surgery. It is not necessary to be a specialist in reproduction to be able to halt cyclicity in a valuable breeding queen using hormones.

EQUIPMENT AND TECHNICAL SKILLS

A sound knowledge of appropriate dosages and criteria for patient selection for all reproductive drugs currently used in feline reproduction is the best guarantee of owner satisfaction and of ensuring the queen's health. Availability of a serum progesterone assay, either in-house or via an external laboratory, is also important, in order to confirm a queen is at an appropriate stage of the reproductive cycle for treatment.

AUDIENCE

This article is aimed principally (but not exclusively) at veterinarians working with cat breeders and whose clientele is increasingly interested in alternative methods of controlling reproduction in pet queens. Surgery is no longer the only choice, and practitioners who manage to keep abreast of new developments will be able to address clients' needs in a modern, professional way.

EVIDENCE BASE

This review draws on a vast body of scientific evidence-based literature. Previously, personal (and sometimes misinformed) opinions, such as the proposed dangerous side effects of progestogens, have been perpetuated in the scientific literature. The papers cited in this review have therefore been carefully scrutinised to distinguish reliable information based on controlled studies from non-evidence-based information.

Prepubertal Use of Long-Term GnRH Agonists in Dogs: Current Knowledge and Recommendations

The search for an alternative approach of estrus control (induction or suppression) in dogs is an important issue and the use of slow GnRH agonist-releasing implants has been the subject of frequent research in recent years. Studies to date demonstrate that the short- and long-term effects of deslorelin implants applicated at different time points of the prepubertal period are similar to those of adult dogs; however, there are important differences. The age of the prepubertal bitch and the dosage appear to be the main determinants of the response to deslorelin, as well as the individual metabolism of the bitch. Recent studies reported that the deslorelin-mediated long-term delay of puberty does not have negative carry-over effects on subsequent ovarian functionality, serum steroid hormone concentrations, uterine health, and fertility; however, more molecular studies are needed to determine the effects of application time of GnRH agonists on hormone concentrations and peripheral receptor expression. Furthermore, the long-term effects of delay of puberty with deslorelin on joint health, tumor development, the immune system, and social behavior deserve further investigations.

A Comparative Study of the Effects of Osaterone Acetate and Deslorelin Acetate on Sperm Kinematics and Morpho-Functional Parameters in Dogs

Simple Summary

Benign prostatic hyperplasia affects over 80% of old, non-castrated male dogs. In many cases, the severity of the symptoms means that treatment is required. The treatment of choice is surgical castration, which is unacceptable for the owners of stud dogs who are interested in therapy that does not exclude their animals from breeding. In those cases, treatment with deslorelin acetate or osaterone acetate offers an alternative to surgery. The aim of our study was to compare the changes in semen parameters over time. The deslorelin acetate implant gradually, during the course of its action, led to a full prevention the stud dogs from mating. However, in the first week following implant placement, in some individuals we observed an increase in sperm concentration (flare up effect), offering the possibility to obtain sperm in valuable dogs before the action of deslorelin acetate is completely established, precluding semen collection. On the other hand, osaterone acetate allowed for the continuous reproductive use of a stud dog, as it only affected some semen parameters, and mainly caused a temporary reduction in semen volume with the subsequent increase in semen concentration without altering the libido.

Abstract

Benign prostatic hyperplasia (BPH) is one of the most common problems in older male dogs that often has a huge impact on their health and welfare. This article presents a comparison between osaterone acetate (Ypozane^®; Virbac^®)(OA) and deslorelin acetate (Suprelorin^®; Virbac^®)(DA), medications that are the main therapeutic alternative to castration in dogs with BPH. Forty dogs were divided into four groups: I—negative control (five dogs without BPH); II—positive control (10 individuals diagnosed with BPH); III—15 dogs treated with DA, and IV—10 individuals treated with OA. Semen fractions were collected on days 0 (day of treatment), 7, 14, and 21, and weeks 8, 12, 16, and 20. Macroscopic, microscopic and CASA analyses were performed. Both DA and OA significantly affected the properties of the canine ejaculate. The DA lead to the lack of libido and had lesser effects to the sperm function before it caused azoospermia, whereas OA had no effect on libido and only temporary reduction in seminal plasma volume was observed, which resulted in temporary deterioration in the percentage of motile and progressive spermatozoa.

Double-Blind, Placebo-Controlled Trial of Cyproterone Acetate to Prevent Flare-Up Effect on Dogs Implanted With Deslorelin

Deslorelin slow-released implants are registered in Europe for the reversible suppression of fertility in male dogs. After administration, a time-limited increase in sex hormones concentration and related behavioral problems may be observed. The aim of this work was to assess whether cyproterone acetate, a synthetic progestogen, can prevent this flare-up effect. Eighteen privately-owned entire male dogs were enrolled in this double-blind, placebo-controlled, randomized clinical trial. All subjects received a 4.7 mg deslorelin implant by SC route and 1-3 capsules containing either cyproterone acetate 2 mg/kg (N = 9) or a placebo (N = 9), by oral route BID for 14 days, depending on the dog's weight. The dogs were followed for 28 days. An increase in the blood testosterone concentration was observed in respectively 9/9 and 7/9 dogs of the control and cyproterone groups (p = 0.47). However, a worsening of the sex hormone related problems (i.e., urinary marking, mounting, aggressiveness toward other dogs and/or escape) was only observed in the placebo group, in 56 or 66% of the dogs as measured by respectively the veterinarian and the owners. Our study suggests that cyproterone acetate is effective and safe to supress the deslorelin induced behavioral flare-up effect, but not the rise in testosterone.

Long-term effect of repeated deslorelin acetate treatment in bitches for reproduction control

Long-acting gonadotropin-releasing hormone (GnRH) analogs, which are approved for male dogs and ferrets, have been used off-label to suppress estrus in bitches predisposed to the side effects of spaying. Health data from the past 12 years were evaluated from bitches without progestogen pretreatment that received deslorelin acetate (DA) to suppress estrus for the first time before the age of 4.5 years. The study population included 32 client-owned bitches repeatedly treated with either 4.7 mg or 9.4 mg DA implants for a period of 5.3 ± 3.4 years (range 0.5-11.3 years). Follow-up information concerning immediate side effects of DA occurring within five months after the first DA treatment (n = 23) as well as long-term side effects of sustained gonadal suppression occurring after five months up to three years (n = 2), three years up to five years (n = 2) or more than five years (n = 8) were assessed through a questionnaire. Treatment was considered successful if no major side effects requiring medical treatment occurred, which applied to 26 out of 32 (81 %) bitches. In the six remaining bitches, the following major side effects led to treatment discontinuation: persistent urinary incontinence (n = 1), reoccurring induced heat (n = 1), uterine disease (n = 3) and/or ovarian tumor (n = 3). The bitches recovered completely after surgical spaying and/or DA implant removal. Minor side effects that did not require therapy or affect animal welfare included body weight changes (n = 18), subtle behavioral changes (n = 13), induced heat (n = 12), coat changes (n = 11), pseudocyesis (n = 6), transient urinary incontinence (n = 4), and/or temporary thickening of the uterine wall with little anechogenic content (n = 2). To examine a possible causal relationship between adverse side effects and DA treatment, further studies should compare the frequency of pathologies between groups of GnRH-treated, intact and spayed bitches of similar breeds and ages. Nevertheless, DA application before the age of 4.5 years may be a means of postponing surgical spaying for several years in breeds at high risk for developing urinary incontinence. Before DA is used in bitches, owners should be fully informed regarding possible side effects.

DESLORELIN (SUPRELORIN®) USE IN NORTH AMERICAN AND EUROPEAN ZOOS AND AQUARIUMS: TAXONOMIC SCOPE, DOSING, AND EFFICACY

The Association of Zoos and Aquariums Reproductive Management Center (RMC) in the US and the European Association of Zoos and Aquaria Reproductive Management Group (RMG) in Europe monitor efficacy of contraceptive products in participating institutions and use those results to inform contraceptive recommendations. This study used the joint RMC-RMG Contraception Database to analyze efficacy of deslorelin implants (Suprelorin^®), a contraceptive used in a wide range of mammalian taxa. More recently its use has increased in birds and in some reptiles and fish. Deslorelin, a gonadotropin-releasing hormone (GnRH) agonist, stimulates the reproductive system before downregulating receptors on pituitary cells that produce hormones that stimulate gonadal steroids in both males (testosterone) and females (estradiol and progesterone), interrupting sperm production and ovulation, respectively. Nevertheless, it has been used mostly in females. Efficacy has been high in mammals, with failures resulting in offspring in only 1.3% of treated individuals and 0.5% of treatment bouts. The failure rate has been higher in birds, with 14.7% of individuals in 7.2% of bouts producing eggs, perhaps reflecting differences in avian GnRH molecules. Too few reptiles and fish have been treated for meaningful analysis. Although deslorelin appears very safe, a possible exception exists in carnivores, because the stimulatory phase can result in ovulation and subsequent sustained progesterone secretion that may cause endometrial pathology. However, the stimulatory phase can be prevented by treatment with megestrol acetate for 7 d before and 7 d after implant insertion. The two current formulations of Suprelorin are effective for minimums of 6 (4.7 mg) or 12 mo (9.4 mg). The data indicate that Suprelorin is an effective and safe contraceptive option for female mammals, although it may not be effective in males of some mammalian species. Further research is needed to ascertain its usefulness in nonmammalian taxa.

Use of GnRH Agonist in Dogs Affected with Leishmaniosis

Sex-associated hormones such as testosterone have been demonstrated to modulate immune responses, which can result in different disease outcomes. The present study was aimed at evaluating the efficacy of a gonadotropin-releasing hormone GnRH agonist implant as deslorelin acetate in association with meglumine antimoniate plus allopurinol in dogs with canine leishmaniosis (CanL). Twenty-two dogs with CanL confirmed by clinical findings and laboratory tests were included in the study. Dogs were randomized into two groups. A control group (CTR, n = 12) was treated with meglumine antimoniate 50 mg/kg SC q 12 h for 28 days plus allopurinol at 10 mg/kg PO q 12 h for the whole study period (six months). An experimental group was treated with allopurinol and meglumine antimoniate, plus an implant of 4.7 mg deslorelin acetate (DES, n = 10). The animals were observed for three months, during which clinical evaluation, indirect fluorescent antibody test (IFAT) titre and testosterone assay were performed on time at day (D)0, 90 and 180. A significantly lower clinical score was recorded in DES than in CTR (p < 0.01) at D90 and D180 (p < 0.01). After 180 days of treatment (D180), a significant reduction of mean levels of IFAT was observed in the DES group (p = 0.03). A highly significant reduction of testosterone (p = 0.01) was observed in the DES group during the study. No statistical correlation between clinical scores, IFAT titres and testosterone within two groups was observed. Data suggested that the agonist of GnRH may be useful in the treatment of CanL.

B-Mode and Doppler Ultrasonographic Findings of Prostate Gland and Testes in Dogs Receiving Deslorelin Acetate or Osaterone Acetate

Simple Summary

This article presents the use of ultrasonography (basic and advanced techniques) in dogs suffering from benign prostate hyperplasia (BPH) for the assessment of the effects of two different medications: osaterone acetate (Ypozane^TM), a registered drug for BPH in dogs, and deslorelin acetate (Suprelorin^TM), registered for pharmacological castration in dogs. Based on the obtained results it can be stated that both B-mode and color Doppler Ultrasound imaging techniques are suitable for diagnosis and progress assessment of dogs suffering from BPH. Both investigated medications (osaterone acetate and deslorelin acetate) led to a significant sonographic improvement. Deslorelin acetate reduced prostate volume more slowly, but its effect lasted longer than for osaterone acetate.

Abstract

This article presents B-mode and color Doppler imaging of the prostate and testes in dogs suffering from benign prostate hyperplasia (BPH), and receiving deslorelin acetate (Suprelorin^TM) or osaterone acetate (Ypozane^TM). The study was planned as a controlled clinical trial, dogs were divided into negative control (healthy dogs, n = 10), positive control (dogs with BPH, n = 10), and study groups, III (n = 15), receiving deslorelin acetate (DA), and IV (n = 10), receiving osaterone acetate (OA). The B-mode appearance of the prostate parenchyma improved in all investigated dogs from the DA group, and in 60% of OA dogs. Prostate volume was reduced more quickly with OA (from D14), but lasting for a shorter time (on average up to week 20), compared to DA that reduced the prostate volume more slowly (>8 weeks), but the reduction remained longer (>24 weeks). The systolic peak velocity (SPV) and mean velocity (Vmean) were higher in all dogs diagnosed with BPH, compared to Control Group I. The indices did not change in both Control Groups I and II, whereas in study Groups III and IV they decreased throughout the study period compared to day 0 and Control Group II. In Group III the highest reduction was noted from day 21 to week 8, whereas in Group IV the lowest Vmean was recorded before day 21. Testicular parenchyma and volume changed significantly in Group III receiving DA, and the velocity of blood flow in the testicular artery correlated positively with testicular volume only in this group (III). The present study proved the usefulness of B-mode and color Doppler US imaging techniques for diagnosis and progress assessment of dogs suffering from BPH. The blood flow kinetics (mainly SPV) demonstrated a time association between the blood flow changes registered in the prostatic artery, and the subsequent volumetric and sonographic improvement of the prostate parenchyma. The reduction in flow indices was noted prior to the reduction in prostate volume, suggesting that the sonographic recovery of the prostate tissue, occurs secondarily to the regression of the prostate vascular system. Both investigated medications (osaterone acetate and deslorelin acetate) led to a significant sonographic improvement. Deslorelin acetate reduced prostate volume more slowly, but its effect lasted longer than for osaterone acetate.

Attempts to downregulate ovarian function in the bitch by applying a GnRH agonist implant in combination with a 3ß-hydroxysteroid-dehydrogenase blocker; a pilot study

Approaches to downregulate ovarian function in the sexually mature bitch by applying slow release GnRH agonist implants are hampered by the initial stimulation of folliculogenesis (flare up) and the resulting side effects. The present pilot study was designed to test to what extent these effects can be suppressed by simultaneous treatment with the 3ß-hydroxysteroid-dehydrogenase (HSD3B) blocker trilostane (T). Treatment with T in 6-h intervals completely blocked adrenal cortisol production. However, in parallel and concomitant with the increase of LH, progesterone and estradiol levels increased, ending up in pro-estric steroid levels in two of the three dogs. Hormonal changes were reflected in the respective clinical symptoms. During the whole observation period the course of LH concentrations did not indicate downregulation of pituitary function as a result of treatment with the GnRH-agonist Suprelorin®, 4.7 mg. The incomplete inhibitory effect of T on the follicular production of sex steroids could be explained by an insufficient transfer of T into the follicular compartment or the existence of a HSD3B isoform in the dog ovary different from the adrenal enzyme. Concerning the lack of downregulation and when accounting for published data different pharmacodynamics/pharmacokinetic activities of GnRH-agonists should be taken into account.

Evaluation of the effects of a 4.7-mg deslorelin acetate implant on egg laying in cockatiels (Nymphicus hollandicus)

OBJECTIVE To evaluate effects of administration of a 4.7-mg deslorelin acetate implant on egg laying in healthy cockatiels (Nymphicus hollandicus). ANIMALS 52 cockatiels. PROCEDURES 26 breeding pairs (a female and its respective male in each pair) were selected on the basis of their history of egg laying. Female birds were sedated and received a 4.7-mg deslorelin acetate implant (n = 13) or placebo implant (13) in the subcutaneous tissues between the scapulae. Male and female birds of each breeding pair were placed in separate but adjacent cages. Birds were exposed to 16 hours of light and 8 hours of darkness. A nest box was placed in cages of female birds to stimulate reproductive activity. Egg production and quality were monitored daily for 365 days. RESULTS Deslorelin acetate implants significantly suppressed egg laying in cockatiels, compared with effects for the placebo implants. Eleven of 13 placeboimplanted birds laid eggs between 12 and 42 days after implantation. None of the deslorelin-implanted birds laid eggs within 180 days after implantation, and only 5 of 13 deslorelin-implanted birds laid an egg during the study period (first egg laid between 192 and 230 days after implantation). No differences in egg quality or number of eggs per clutch were observed between the 2 groups. CONCLUSIONS AND CLINICAL RELEVANCE Insertion of a 4.7-mg deslorelin acetate implant suppressed egg laying in healthy cockatiels for at least 180 days. Studies are necessary to evaluate effects of a deslorelin acetate implant in other avian species or in association with reproductive disorders.

Clinical use of deslorelin (GnRH agonist) in companion animals: a review

Over the years, many contraceptive medications have been developed for companion animals, but many secondary adverse effects have limited their use. A major advancement was achieved with the use of gonadotropin-releasing hormone (GnRH) analogues, mainly GnRH agonists, which mimic the effects of native GnRH. The development of effective low-dose, slow-release implants with potent agonists such as deslorelin (Suprelorin®, Virbac) have allowed their use to become widespread in recent years, with many potential benefits in companion animals. While the major application of deslorelin was initially male contraception, due to its two differing actions, either the stimulation of oestrus or the sterilization of fertility, its use has been increasing in the bitch as well. The aim of this study is to review the applications of deslorelin GnRH agonist implants in companion animal, such as dogs, cats and some exotic pets.

Use of GnRH-agonists for medical management of reproductive disorders in birds

Pet birds suffer from a wide range of reproductive conditions and diseases. Chronic egg laying, egg binding, and excessive reproductive activities are common problems. Veterinarians may prescribe behavior modification, changes in captive care, and medical therapy to curb these behaviors. Surgical removal of the oviduct is effective at stopping egg production; however, it is a specialized surgery that carries surgical and anesthetic-related risks. The inability to surgically remove the ovary in birds may result in persistent ovarian activity and secondary complications. Therefore, hormone therapy as an adjunct or main therapeutic approach, using sustained-release GnRH agonists, shows promise in pet birds.

Challenges for diagnosis and control of cystic hydatid disease

This paper is based on the experience of the authors, with the aim to define the challenges for Echinococcus granulosus (E.g./CE) diagnosis and control for those countries that may now or in the future be contemplating control of hydatid disease. A variety of methods are available for diagnosis in humans but a universal gold standard is lacking. Diagnosis in definitive hosts can avoid necropsy by the use of methods such as coproantigen detection but test performance is variable between populations. A sylvatic cycle adds challenges in some countries and the epidemiology of the parasite in these hosts is poorly understood. Control by solely administering praziquantel to dogs is not effective in developing countries where the disease is endemic. Additional avenues to pursue include the instigation of participatory planning, use of an existing vaccination for intermediate hosts and development of a vaccine and long-acting anthelmitic implants for definitive hosts. Promoting public acceptance of control of the dog population by humane euthanasia and reduced reproduction is also essential.