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in prostatic size as detected by ultrasonography
within 10 days. When administered to research dogs
at 5 mg/kg/day PO for 1 year, it did not alter libido or sperm production31. Also flutamide is a human drug not approved for use in veterinary medicine, although it appears safe, effective and well tolerated in dogs.
GnRH agonists - Following administration of a GnRH agonist, prostatic size decreases in parallel with
the decrease of testosterone. When adult dogs are implanted with 4.7 or 9.4 mg deslorelin their prostatic volume decreases more than 50% from week 6 onwards32-33, and serum T concentrations decreases 90% from week 3 onwards34. We have observed disappearance of conspicuous (>17 mm diameter) prostatic cysts following treatment with a single 4.7 mg deslorelin implant35 as well as of larger (20x25 mm) prostatic cysts in adult male dogs with clinical signs of benign prostatic hypertrophy undergoing treatment with a 4.7 mg deslorelin acetate administered every 6 months (unpublished observation). In milder or less complicated cases of BPH, an improvement of the clinical situation
of treated dogs is observed often without any additional pharmacological treatment already at the first follow-
up visit. In cases in which prostatic size is markedly increased and in the presence of rectal or urethral constriction or other signs of discomfort, deslorelin may cause a temporary worsening of the clinical situation because of the initial (first week) rise in testosterone secretion due to temporary hypersecretion of pituitary gonadotrophins (flare effect); in these cases we normally add a 2-week course of a progestogen derivative such as cyproterone acetate. The mechanism of action of GnRH agonists in achieving a decreased prostatic size is probably through the decrease in serum testosterone, which also cause a (reversible) sterility. Therefore, GnRH agonists should not be used for the treatment of BPH in male dogs intended to be used for breeding.
Clinical management of canine BPH
The best way to prevent the development of clinical BPH in the dog is to identify its early pre-clinical
signs by performing a regular monitoring of prostatic conditions by ultrasound. If signs of BPH (such as presence of prostatic cysts or increased prostatic size) are observed during a routine check while the dog
is asymptomatic, owners should be advised to watch for the development of clinical signs in order to start treatment as soon as possible. There is little information on the value of a preventive treatment for BPH in the dog. In men, preventive treatment is often discouraged because of the many side effects which may be caused by alpha-1 adrenergic antagonists (the most common treatment for human BPH). However, incidence of
side effects of such drugs in the dog is unknown, and most importantly alpha-1 adrenergic antagonists are not 1st-choice drugs for canine BPH, while steroidal or non-steroidal antiandrogens or GnRH agonists are
more indicated for this purpose. Side effects of long term treatment with steroidal antiandrogen include termporary adrenocortical suppression and a decrease in libido and semen quality. All steroidal antiandrogens should be avoided in breeding animals because of their potential negative impact on fertility. However, the use of medroxyprogesterone acetate (4 mg/kg SC every 3-5 months), chlormadinone acetate (0.1-0.3 mg/kg/day per os for 6 months) as well as osaterone acetate in its well known weekly treatment regimen have been associated with a normal or acceptable fertility in male dogs at least for the first few weeks and therefore might be used for limited amounts of time in these patients.
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