Control of reproduction and of undesirable social and sexual behaviour in dogs and cats

Effects of delmadinone acetate on pituitary-adrenal function, glucose tolerance and growth hormone in male dogs

OBJECTIVE

To characterise the effects of delmadinone acetate on the pituitary-adrenal axis, glucose tolerance and growth hormone concentration in normal male dogs and dogs with benign prostatic hyperplasia.

DESIGN

A prospective study involving nine normal male dogs and seven with prostatic hyperplasia.

PROCEDURE

Delmadinone acetate was administered to six normal male dogs and seven dogs with benign prostatic hyperplasia at recommended dose rates (1.5 mg/kg subcutaneously at 0, 1 and 4 weeks). Three normal controls received saline at the same intervals. Blood concentrations of ACTH, cortisol, glucose, insulin and growth hormone were measured over 50 days. Intravenous glucose tolerance and ACTH response tests were performed before and after treatment in the nine normal animals.

RESULTS

A substantial suppression of basal and 2 h post-ACTH plasma cortisol secretion was demonstrated after one dose in all dogs given delmadinone acetate. Individual responses after the second and third administration varied between recovery in adrenal responsiveness to continued suppression. Plasma ACTH concentration was also diminished after one treatment. No effects were evident on glucose tolerance or serum growth hormone concentrations.

CONCLUSION

Delmadinone acetate causes adrenal suppression from inhibition of release of ACTH from the pituitary gland. Treated dogs may be at risk of developing signs of glucocorticoid insufficiency if subjected to stressful events during or after therapy. Neither glucose intolerance nor hypersomatotropism seems likely in male dogs given delmadinone acetate at the recommended dose rate, but the potential for excessive growth hormone secretion in treated bitches remains undetermined.

Influence of orchiectomy on canine behaviour

One hundred and twenty-two dog owners were interviewed to obtain information about the effects of orchiectomy on the behaviour, unwanted side effects, and testosterone-dependent disease processes in their dogs. Behavioural problems were the main reason for orchiectomy, unwanted sexual behaviour being the most common, together with roaming, aggression, and abnormal urination behaviour. Objectionable sexual behaviour, inter-male aggression, roaming, and abnormalurination were reduced after orchiectomy in approximately 60 per cent of the dogs. The side effects of orchiectomy included increased bodyweight, increased appetite and decreased activity in less than 50 per cent of the dogs, and there was a significant relationship between increased appetite and bodyweight. The clinical signs of testosterone-dependent disease in most of the dogs either decreased or disappeared after orchiectomy.

Treatment of problem behaviour in dogs and cats by castration and progestagen administration: a review

Treatment of problem behaviour in companion animals by castration and progestagen administration is reviewed. In male dogs castration is effective in eliminating roaming and, to a lesser extent, mounting, urine marking and intermale aggression. Spraying, roaming and fighting behaviour in cats disappear almost completely after castration. In the latter species prepubertal castration does not seem to be more effective in preventing this problem behaviour than postpubertal castration is in eliminating it. In dogs, intermale aggression, urine marking, mounting and roaming have been treated successfully with progestagens; in cats the same treatment has been successful in decreasing fighting and roaming. There are no reports on the ethical aspects or on adverse side effects of castration. For progestagens a wide range of undesirable side effects have been described. The results of both castration and progestagen therapy differ in the various studies. The underlying mechanism(s) of progestagen influence on behaviour are not understood. Therefore, future research on this topic is necessary.

Medroxyprogesterone acetate and reproductive processes in male dogs

The treatment of normal male dogs with a depot preparation of medroxyprogesterone acetate (4 mg/kg) for 7 weeks reduced peripheral testosterone levels by 58%. No effects on testicular size and consistency, semen quality or libido were found.

Implant pellets I: effects of compression pressure on in vivo dissolution of delmadinone acetate pellets

A formulation containing 95% delmadinone acetate was compressed at three different pressures. These pressures resulted in a pellet density difference of 19%. In vivo dissolution profiles were determined for five lots of pellets. The pellets were implanted subcutaneously in rats, removed periodically, and assayed chemically for remaining steroid. The resulting data were fit, using the computer program NONLIN, to a dissolution model. The dissolution rate for the lot with the lowest density made at the lowest compression was statistically (p less than 0.05) different from the four other lots. A possible explanation for this increased dissolution rate could be that channeling occurs within the pellet, thereby increasing the effective dissolving surface. The results also indicate that equivalent dissolution rates between lots are reached at a certain compression and density.