Low-dose megestrol acetate revisited: a viable adjunct to surgical sterilization in free roaming cats?

Approximately 2-3 million cats are euthanased in animal shelters across the United States annually. Preventing pregnancy in cats is a key step to reducing this number. While surgery is generally a safe and effective tool for curbing reproduction in cats, it is not a practical method to achieve the reduction in numbers required for an appreciable impact on the cat population as a whole. Low-dose megestrol acetate (MA) is a synthetic progestin that has been used for the management of reproduction in free roaming cat populations; however, there has been no regulatory oversight regarding the use of this product for this purpose. Additionally, there is a paucity of data regarding the safety and efficacy of the product for the management of reproduction in free roaming cats. The purpose of this review is: (1) to outline the need for a non-surgical contraceptive in cats; (2) to discuss the uses of MA in domestic cats; (3) to consider potential adverse effects of the drug, and (4) to discuss regulatory challenges associated with the use of MA in free roaming cat populations. In order to answer the questions posed in this review, more data will need to be collected in laboratory and field studies.

An enzymatic method to determine γ-hydroxybutyric acid in serum and urine.

BACKGROUND: Gamma-hydroxybutyric acid (GHB) has become one of the most dangerous illicit drugs of abuse today. It is used as a recreational and date rape drug because of its depressant effect on the central nervous system, which may cause euphoria, amnesia, respiratory arrest, and coma. There is an urgent need for a simple, easy-to-use assay for GHB determination in urine and blood. In this article, a rapid enzymatic assay adapted to clinical chemistry analyzers for the detection of GHB is presented. METHODS: The described GHB enzymatic assay is based on a recombinant GHB dehydrogenase. The full validation of the assay was performed on a Konelab 30 analyzer (Thermo Fisher Scientific). RESULTS: The analytical sensitivity was <1.5 mg/L, whereas the functional sensitivity was 4.5 mg/L in serum and 2.8 mg/L in urine. The total imprecision coefficient of variation (CV) was <9.8% in serum and <7.9% in urine. The within-run imprecision showed a CV of <3.8% in serum and <4.6% in urine. The assay was linear within the range 5-250 mg/L. Mean recoveries were 109% in serum and 105% in urine. No cross-reactivity was observed for tested GHB analogues and precursors. Comparison of GHB-positive samples showed an excellent correlation with ion chromatography, gas chromatography-mass spectrometry, and liquid chromatography associated to tandem mass spectrometry. Except for ethanol, no substantial interference from serum constituents and some drugs was observed. CONCLUSIONS: This automated GHB assay is fully quantitative and allows the accurate measurement of GHB in serum and urine. It can be used as a rapid screening assay for the determination of GHB in intoxicated or overdosed patients.

Spaying-induced coat changes: the role of gonadotropins, GnRH and GnRH treatment on the hair cycle of female dogs.

Although spaying can result in qualitative hair coat changes in dogs, the influence of spaying on the hair growth cycle has never been described. The study aims were to examine the effect of spaying and gonadotropin-releasing hormone (GnRH) treatment on canine hair coat, cycle stages of hair follicles, plasma gonadotropin concentrations and mRNA transcription of luteinizing hormone (LH) and GnRH receptors in hair follicles. Fifteen female dogs were examined before and 1 year after spaying and 24 spayed dogs before and after GnRH treatment. Spaying resulted in increased plasma gonadotropin concentrations and increased anagen : telogen ratio of hair follicles, but only 20% of the dogs developed coat changes. No differences were found in mRNA transcription of LH and GnRH receptors. GnRH treatment resulted in reduced plasma gonadotropin concentrations and improvement of coat changes in 79% of patients. This was associated with an increase in catagen hair follicles without changes in the anagen : telogen ratio. The present study demonstrated that spaying had an effect on the anagen : telogen ratio of hair follicles. Spaying-induced coat changes did not correlate with the anagen : telogen ratio. GnRH treatment reduced gonadotropin concentrations and reversed coat changes in some dogs, but had no effect on the hair growth cycle other than increasing the number of catagen hair follicles. A weak positive correlation between the plasma LH concentration and the anagen : telogen ratio was noted; however, our data did not suggest a direct receptor-mediated hormonal effect on the hair follicle. The present study did not identify the pathomechanism of spaying-induced coat changes.

Urodynamic parameters and plasma LH/FSH in spayed Beagle bitches before and 8 weeks after GnRH depot analogue treatment.

The pathophysiology of urinary incontinence due to spaying remains unknown. Incontinent bitches can be treated successfully with depot preparations of GnRH-analogues and there are differences in plasma gonadotropin levels between continent and incontinent spayed bitches. It is therefore assumed that the supraordinated hormones, GnRH, FSH, and/or LH, have an effect on the urodynamic parameters. In this study, the potential influence of these hormones on the lower urinary tract was investigated by measuring urethral pressure profiles and cystometry. Simultaneously, plasma concentrations in 10 spayed Beagle bitches were determined 5 weeks prior to and 8 weeks after treatment with the GnRH analogue leuprolide. Within 1 week of GnRH analogue administration, plasma FSH and LH levels decreased from 72.5 and 7.7 to 7.75 and 0.72ng/mL, respectively. These plasma gonadotropin levels correspond with those of intact bitches during anoestrus. Urethral pressure profiles indicated that the treatment had no significant effect on maximum urethral closure pressure, functional and total length of the urethra, or area of the closure pressure curve. The data obtained by cystometry regarding mean bladder threshold volume showed a significant increase from 109 to 172mL. The improvement in bladder function after the application of GnRH-application is presumably a direct effect of the GnRH as a relationship between the plasma gonadotropin levels and the urodynamic parameters could not demonstrated.

Effect of a long acting GnRH analogue or placebo on plasma LH/FSH, urethral pressure profiles and clinical signs of urinary incontinence due to Sphincter mechanism incompetence in bitches.

In 23 bitches with urinary incontinence due to spaying, the effect of treatment with a long-acting formulation of leuprolide acetate on frequency of incontinence, plasma gonadotropin levels and urodynamic parameters was evaluated. In addition, the clinical effect was compared with that of treatment with alpha-adrenergics. Before treatment, the dogs' incontinent episodes occurred, on average, 4 times per day on up to 6 days per week. In the pre-trial after therapy with phenylpropanolamine (n=23) the episodes of incontinence decreased by 92%, in the double-blind study 5 weeks after GnRH-analogue (n=11) by 71%; and by 28% after the placebo (n=12). By the end of the study, nine of twenty-two leuprolide treated bitches responded completely to treatment and were continent for periods lasting 70-575 days after treatment. In another 10 dogs, response to therapy was partial and the frequency of incontinence was reduced by at least 50%. After therapy with placebo, one bitch had no episodes of incontinence for 412 days. Treatment with the GnRH-analogue significantly decreased the plasma gonadotropin levels but there was no correlation between the effect on gonadotropin levels and response to treatment. Treatment with leuprolide or placebo had no effect on urethral closure pressure regardless of the response to treatment. The hypothesis that the change of the plasma gonadotropin levels after spaying is the cause of reduced urethral closure function was not supported by the results of this study. A possible direct effect of GnRH-analogues on the bladder is discussed. Long acting GnRH analogues appear to be a well-tolerated alternative for urinary incontinence treatment, but they appear to be less effective than the alpha-adrenergics.

GnRH-agonist induction of fertile estrus with either natural mating or artificial insemination, followed by birth of pups in gray wolves (Canis lupus).

Although captive populations of endangered species such as the Mexican gray wolf (Canis lupus baileyi) can benefit from artificial insemination to accomplish genetic exchange, reliable techniques for timing insemination are lacking. We used the generic gray wolf (C. lupus) to test the efficacy of a short-acting GnRH-agonist implant, deslorelin, for inducing estrus. Of five females receiving implants on 17 or 18 January 2003, two mated naturally 10-17 days later, and the others were artificially inseminated using fresh semen, one on day 7 and all three on day 11. Relaxin tests revealed that one artificially inseminated female and both naturally mated females were pregnant on 1 March, and all three gave birth to healthy puppies on 4-6 April. Of the artificially inseminated females, only the one who subsequently conceived and gave birth was judged to be in cytologic estrus at the time of insemination. Two females were treated again with deslorelin on 12 January 2004, followed by collection of fecal samples for hormone analysis. One female, who was housed with a male, copulated on day 17 but did not conceive; the other was not with an adult male. Fecal progestin and estrogen profiles suggested that estrus, but not ovulation, was induced. These results indicated that deslorelin could induce fertile estrus in the gray wolf, although individual response varied. Further investigation is needed to better define and control the interval between implant insertion and ovulation for optimal timing of insemination.

Long-term suppression of fertility in female giraffe using the GnRH agonist deslorelin as a long-acting implant.

Zoological institutions provide an environment conducive to studying proximate mechanisms influencing reproduction that can provide guidance to both field and captive settings seeking to manage their stock. Both national parks and zoos have space limitations that sometimes require the use of reversible contraception in order to reduce reproductive rate or limit specific individuals from reproducing. We designed a study to test the efficacy of a long-lasting contraceptive in female giraffe by monitoring reproductive endocrinology and behavior. We implanted two animals with the GnRH agonist deslorelin and monitored their endocrine status using fecal steroid analysis. We have previously validated an assay for fecal pregnanes and here we report our validation for fecal estrogens. Both sex steroid concentrations were suppressed in two females, although one female exhibited an immediate post-implantation positive feedback response. Sexual activity nearly disappeared in one animal, whereas the other showed regular sexual behavior. The contraceptive effect lasted for at least 472 d, and successfully suppressed estrous cyclicity in one female for >2 y. We conclude that deslorelin implants provide a minimally invasive means for long-term suppression of reproduction in female giraffe.

Clinical and endocrine responses to treatment with deslorelin acetate implants in ferrets with adrenocortical disease.

OBJECTIVE: To evaluate the clinical and endocrine responses of ferrets with adrenocortical disease (ACD) to treatment with a slow-release implant of deslorelin acetate. ANIMALS: 15 ferrets with ACD. PROCEDURE: Ferrets were treated SC with a single slow-release, 3-mg implant of deslorelin acetate. Plasma estradiol, androstenedione, and 17-hydroxyprogesterone concentrations were measured before and after treatment and at relapse of clinical signs; at that time, the adrenal glands were grossly or ultrasonographically measured and affected glands that were surgically removed were examined histologically. RESULTS: Compared with findings before deslorelin treatment, vulvar swelling, pruritus, sexual behaviors, and aggression were significantly decreased or eliminated within 14 days of implantation; hair regrowth was evident 4 to 6 weeks after treatment. Within 1 month of treatment, plasma hormone concentrations significantly decreased and remained decreased until clinical relapse. Mean time to recurrence of clinical signs was 13.7 +/- 3.5 months (range, 8.5 to 20.5 months). In 5 ferrets, large palpable tumors developed within 2 months of clinical relapse; 3 of these ferrets were euthanatized because of adrenal gland tumor metastasis to the liver or tumor necrosis. CONCLUSIONS AND CLINICAL RELEVANCE: In ferrets with ACD, a slow-release deslorelin implant appears promising as a treatment to temporarily eliminate clinical signs and decrease plasma steroid hormone concentrations. Deslorelin may not decrease adrenal tumor growth in some treated ferrets. Deslorelin implants may be useful in the long-term management of hormone-induced sequelae in ferrets with ACD and in treatment of animals that are considered at surgical or anesthetic risk.

FSH and LH plasma levels in bitches with differences in risk for urinary incontinence.

To determine whether the height of the plasma gonadotropin levels after spaying is associated with urinary incontinence, the concentrations of plasma follicle stimulating hormone (FSH) and luteinizing hormone (LH) were determined once in 191 intact and 308 spayed bitches. The bitches were grouped according to their risk for urinary incontinence and the medians of their respective gonadotropin levels were compared. For intact anestrous bitches, the FSH- and LH-plasma concentrations were 5.2 (4, 8) ng/mL (median (Q1, Q3)) and 0.5 (0.5-0.5) ng/mL, respectively. In the first year after spaying, the gonadotropin concentrations rose significantly, then stabilised at a level around 10 times those of intact bitches (FSH 62.5 (44, 91) ng/mL; LH 6.1(4, 11) ng/mL). The plasma gonadotropin concentrations of long-term spayed (>12 months) continent bitches (n=209) were higher (FSH 66.8 (46, 104) ng/mL; LH 6.5 (4, 11) ng/mL) than in spayed incontinent bitches (n=60) (FSH 51.5 (38, 74) ng/mL; LH 5.5 (3, 8) ng/mL), the latter also had a higher body weight. Multiple regression analysis showed that the FSH-plasma concentration and not the body weight was decisive for the occurrence of urinary incontinence. The results of this study suggest that levels of gonadotropins are associated, directly or indirectly in the pathophysiology of urinary incontinence after spaying.

Changes in plasma gonadotropin concentrations and urethral closure pressure in the bitch during the 12 months following ovariectomy.

Urinary incontinence due to acquired urethral sphincter incompetence is a common side effect of spaying, for which the underlying cause remains unknown. Spaying not only results in a significant reduction in the urethral closure pressure within 1 year but also in an increase in the plasma gonadotropin concentrations. To investigate the possible link between the post-ovariectomy changes in plasma gonadotropins and in urethral closure pressure, gonadotropin and urodynamic measurements were performed in 10 Beagle bitches before and for a period of 1 year after spaying. Plasma gonadotropin concentrations rose quickly after ovariectomy and peak levels were seen within 3-5 weeks, followed by a sharp drop until week 10. A steady increase was observed subsequently until week 42, when a plateau was reached. One year after spaying, the mean FSH concentration was 75.3 +/- 32.1 ng/ml, a 17-fold increase, and the LH was 8.3 +/- 3.8 ng/ml, an eightfold increase over the pre-spaying values. Ten months after spaying, the mean urethral closure pressure (9.7 cm H2O) was significantly reduced when compared to the mean pre-operative value of 15.4 cm H2O. However, there was no clear relationship between the gonadotropin concentrations and the urethral closure pressure. From these results it seems unlikely that chronically elevated gonadotropins are the underlying cause for reduced urethral closure pressure after spaying resulting in urinary incontinence.