Finasteride and tamsulosin used in benign prostatic hypertrophy: a review of the prescription-event monitoring data.

OBJECTIVE: To review the results of non-interventional observational cohort studies of 14 772 patients treated with finasteride and 12 484 patients treated with tamsulosin, both studies being of national proportions and undertaken in general medical practice in England. METHODS: Both studies were undertaken by prescription-event monitoring (PEM), whereby the exposure data are derived from information provided in strict confidence by the Prescription Pricing Authority of the National Health Service. The outcome data are derived from 'green form' questionnaires completed by the prescribing general practitioners (GPs). Additional data are obtained by medical follow-up with the attending practitioners. Adverse experience was measured in three ways; as reports of events which the doctors considered to represent adverse drug reactions; as reports of reasons for stopping the drug; and by studying the incidence density of each reported event. For these purposes a computerized dictionary containing 1430 higher level terms was used. The duration of exposure in the finasteride study was approximately 1 year and was approximately 6 months in the tamsulosin study. RESULTS: The outcome data on the 14 772 and 12 484 patients treated in the finasteride and tamsulosin studies were derived from the 63% and 57.4% of the green forms sent out and returned, respectively. The finasteride cohort included two women and the tamsulosin cohort 70 women. The mean (SD) age of the men in the two cohorts was, respectively, 69.0 (9.2) and 66.2 (11.7) years. Both drugs were well tolerated on long-term therapy and 69.6% (10 274 patients) of the total finasteride and 62.0% (7739 patients) of the total tamsulosin cohort were still receiving the drug at the end of 6 months. In the finasteride study, impotence or ejaculatory failure was reported in 2.0% of the patients still receiving the drug; there were reports of decreased libido in 1.0% and gynaecomastia was reported whilst the drug was still being prescribed in 39 patients (0.3% of the cohort). With tamsulosin, uncommon cases of dizziness, headache, malaise and hypotension (89 reports in 12 484 patients, i.e. 0.7% of the cohort) were common to the findings of reported adverse reactions, reasons for stopping the drug and events of highest incidence density. None of the deaths which occurred in either of these large cohorts was attributed by either the reporting GPs or the PEM medical staff to the drugs examined. Conclusion The GPs rated the drugs effective in most patients; tolerance and adverse experience was consistent with the known pharmacology of the two drugs. No serious, unexpected adverse effects were identified.

A pharmacoeconomic analysis of patients with symptoms of benign prostatic hyperplasia.

A pharmacoeconomic analysis of therapies for patients with benign prostatic hyperplasia (BPH) was conducted. The therapies compared were androgenic hormone inhibition (finasteride) and alpha-blockade (doxazosin, prazosin and terazosin). This was a cost-effectiveness analysis from the perspective of the US military. The 36-month decision-tree model considered the aforementioned drugs as initial therapy for BPH following an unsuccessful period of watchful waiting. Therapy was continued toward a successful response. All patients who did not respond to therapy received secondary interventions, including transurethral resection of the prostate (TURP). The main outcome measures were clinical effectiveness and incurred costs. A Monte Carlo sensitivity analysis was performed on all cost-effectiveness ratios. The model and sensitivity analysis supported prazosin as the most cost effective alpha-blocker over finasteride: the mean difference was $US381.65 (1994 values) per successfully treated patient, with a range of $US57.83 to $US675.53, in favour of prazosin. If prazosin was used as initial drug therapy after watchful waiting for a man over 50 years of age with classical symptoms of prostatism and no other severe or confounding comorbid conditions, a cost of $US578.15 per treatment could be expected, with clinical effectiveness of 70.3%. Patients who cannot tolerate prazosin should be considered for terazosin therapy before moving on from alpha-blockers. Subsequent treatment with finasteride would cost $US1426.53, with an additional clinical effectiveness of 9.9%. For the small number of patients who fail both therapies, the cost effectiveness of a first TURP as 'third-line' intervention [$US4321.36 for an additional effectiveness of 8.62% and a repeat TURP as 'fourth-line' ($US7650.54 for 0.59%) interventional] was calculated in a similar manner. Costs were cumulative, and effectiveness was derived from the total number of patients who started prazosin therapy. Pharmacological therapy was more cost effective than surgical intervention, and alpha-blockers were more cost effective than finasteride. Among the alpha-blockers, prazosin was by far the most cost effective followed by terazosin, then doxazosin.

Comparison of the effects of the 5 alpha-reductase inhibitor finasteride and the antiandrogen flutamide on prostate and genital differentiation: dose-response studies.

Studies were performed to compare the effects of 5 alpha-reductase inhibition and antiandrogen receptor blockade on differentiation of male internal and external genital structures and prostate in the rat. Dose-response studies were performed on male rats treated in utero during the period of sexual differentiation with either the potent 5 alpha-reductase inhibitor finasteride or the antiandrogen flutamide. The treated animals were raised to adulthood and killed, and genital structures were evaluated. Treatment with the 5 alpha-reductase inhibitor finasteride at a dose of 25 mg/kg.day resulted in significant feminization of the external genitalia. There was no further feminization of the genitalia at doses up to 300 mg/kg.day. Wolffian ductal differentiation occurred at all doses evaluated. Seminal vesicle weight, however, significantly decreased at 25 mg/kg.day, but without a further decrease at higher doses of the 5 alpha-reductase inhibitor. Vas deferens and epididymal weights were unchanged at all doses evaluated. There was a significant decrease in prostate size at 25 and 50 mg/kg.day, with no further decrease at higher doses. In flutamide-treated animals, complete feminization of the genitalia occurred at 24 mg/kg.day in all animals. At 18 mg/kg.day, Wolffian ductal differentiation occurred, but seminal vesicle weight was decreased. At dosages of 100, 200, and 300 mg/kg.day flutamide, the vas deferens was absent unilaterally or bilaterally, with small remnants of epididymal head and tail present. At dosages of 24 mg/kg.day and above, the prostate was absent. Studies with the 5 alpha-reductase inhibitor finasteride demonstrate the dependency of prostate and male external genital differentiation on dihydrotestosterone (DHT). However, unlike androgen receptor blockade with flutamide, finasteride did not totally abolish prostate differentiation or completely feminize the external genitalia, despite increasingly higher doses. Since there is no evidence of multiple 5 alpha-reductase isoenzymes to date in the rat, these results suggest that testosterone (T) can compensate for DHT to some degree at the level of the androgen receptor. Wolffian differentiation, however, was not affected by inhibition of DHT, demonstrating its T dependency, but seminal vesicle growth was impaired. Thus, inhibition of 5 alpha-reductase activity limits seminal growth potential in adulthood. Studies with the antiandrogen flutamide show that at doses significantly above that required to completely block prostate differentiation and cause genital feminization, Wolffian ductal differentiation is significantly impaired. Thus, higher doses of flutamide are needed to block the paracrine effect of T on the Wolffian ducts.

Finasteride-associated male infertility.

Finasteride is a potent and specific inhibitor of the alpha-reductase enzyme in men. Clinical studies have shown that finasteride 1mg/day is effective for promoting hair growth in men with male pattern hair loss. However, there is a concern about the use of finasteride, especially in young fertile patients, because of its action on testosterone metabolism. This paper describes 3 cases of young patients who had very poor seminal quality during finasteride treatment (1 mg/day), and their seminal quality greatly improved after cessation of finasteride treatment. Two of them presented with a left varicocele and the other was obese. We hypothesize that finasteride may not dramatically change the spermatogenesis process in healthy men, but in patients with conditions related to infertility, an amplification of the negative influence of finasteride could occur. Future studies should be done to clarify the extent of the effect of finasteride in patients fertility problems.