Effect of tamsulosin on urethral tone in healthy male cats.

OBJECTIVES: Alpha-adrenergic antagonists are commonly used to prevent recurrent urethral obstruction in cats with mixed reports of efficacy. No published data on tamsulosin use in cats are available. The objective of this study was to measure changes in urodynamic parameters and blood pressure in five healthy male cats before and after administration of tamsulosin orally for 4 and 10 days. METHODS: Five young healthy adult male cats from a research colony were administered tamsulosin at 0.1 mg/cat PO q24h for 10 days. Urethral pressure profile and blood pressure measurements were performed before treatment and approximately 6 h after treatment on days 4 and 10. Maximum urethral closure pressure (MUCP) for the prostatic and penile urethra, functional urethral length (FPL), functional area (FA) and systolic blood pressures were recorded and compared between the time points. RESULTS: Significant changes in blood pressure on day 4 (121.1 mmHg ± 20.2 mmHg) and on day 10 (112.6 mmHg ± 14.9 mmHg) compared with day 0 (141.1 mmHg± 33.4 mmHg) were not detected (P = 0.18) in anesthetized cats. No significant difference in MUCP, FA or FPL measurements were detected among baseline, day 4 and day 10 of treatment. Hematuria and transient pollakiuria were induced in two cats with 3.5 Fr urethral catheters. CONCLUSIONS AND RELEVANCE: Tamsulosin at 0.1 mg/cat PO q24h did not induce hypotension in healthy cats. Urodynamic testing performed 6 h after the tamsulosin pill was administered did not detect consistent decreases in urodynamic functions induced by tamsulosin. Repeated catheterization of tom cats with 3.5 Fr catheters may induce significant urethral trauma.

Total thyroxine and thyroid-stimulating hormone responses of healthy cats to different doses of thyrotropin-releasing hormone.

Thyrotropin-releasing hormone (TRH) stimulation can be used as a test of thyroid function and pituitary thyrotropin (thyroid-stimulating hormone, TSH) reserve, but optimal stimulation testing protocols in cats are unreported. We randomly divided 6 healthy young adult cats into 3 groups of 2 and administered 3 different intravenous doses of TRH (0.01, 0.05, 0.1 mg/kg) at weekly intervals in our crossover study. Serum TSH and thyroxine (T4) concentrations were measured using chemiluminescent immunoassay before, and at 30 and 60 min after, TRH administration. All cats were monitored for 4 h post-TRH administration for side effects. All 3 TRH doses induced significant TSH (0.01 mg/kg, p = 0.001; 0.05 mg/kg, p = 0.002; 0.1 mg/kg, p = 0.006) and total T4 (0.01 mg/kg, p = 0.008; 0.05 mg/kg, p = 0.006; 0.1 mg/kg, p = 0.001) responses. Lower TRH doses (0.01 and 0.05 mg/kg) caused fewer side effects (1 of 6 cats) than did the highest dose (3 of 6 cats), and may be safer in cats than the previously reported higher dose (0.1 mg/kg) of TRH. Our results do not support the use of maropitant to prevent side effects of a TRH stimulation test in cats.