Pharmacokinetic interaction between finasteride and terazosin, but not finasteride and doxazosin

WITHDRAWN: Terazosin for benign prostatic hyperplasia

BACKGROUND

Lower urinary tract symptoms associated with benign prostatic obstruction (BPO) occur in up to 70% of men over the age of 60 years. To relieve these bothersome symptoms, treatment options include alpha-antagonists, also know as alpha-blockers.

OBJECTIVES

We conducted a systematic review to evaluate the effectiveness and adverse effects of the alpha-blocker, terazosin, for treatment of urinary symptoms associated with BPO.

SEARCH STRATEGY

Trials were searched in computerized general and specialized databases (MEDLINE, Cochrane Library), by checking bibliographies, and by contacting manufacturers and researchers.

SELECTION CRITERIA

Studies were included if they (1) were randomized trials of at least 1 month duration, and (2) included men with symptomatic BPO and compared terazosin with placebo or active controls.

DATA COLLECTION AND ANALYSIS

Study, patient characteristics and outcomes data were extracted in duplicate onto standardized forms utilizing a prospectively developed protocol. The main outcome measure for comparing the effectiveness of terazosin with placebo or other BPO medications was change in urological symptoms as measured by validated symptom scores. Secondary outcomes included urodynamic measures. The main outcome measure for adverse effects was the number of men reporting side effects. We also evaluated the number of men withdrawing from treatment and the number withdrawing due to adverse effects.

MAIN RESULTS

Seventeen studies involving 5151 subjects met inclusion criteria (placebo-controlled (n = 10); alpha-blockers (n = 7); finasteride alone or in combination with terazosin as well as placebo (1); microwave therapy (TUMT) (1). Study duration ranged from 4 to 52 weeks. Mean age was 65 years and 82% of men were white. Baseline urologic symptom scale scores and flow rates demonstrated that men had moderate BPO. Efficacy outcomes were rarely reported in a fashion that allowed for data pooling but indicated that terazosin improved symptom scores and flow rates more than placebo or finasteride and similarly to other alpha antagonists. The pooled mean percentage improvements for the Boyarsky symptom score was 37% for terazosin versus 15% for placebo (n = 4 studies). The mean percentage improvement for the American Urological Association symptom score (AUA) was 38% compared to 17% and 20% for placebo and finasteride, respectively (n = 2 studies). The pooled mean improvement in the International Prostate Symptom Score (IPSS) (40%) was similar to tamsulosin (43%). Peak urine flow rates improved greater with terazosin (22%), than placebo (11%) and finasteride (15%) but did not differ significantly from the other alpha-blockers. The percentage of men discontinuing terazosin was comparable to men receiving placebo and finasteride but was greater then with other alpha-antagonists. Adverse effects were greater than placebo and included dizziness, asthenia, headache, and postural hypotension.

AUTHORS' CONCLUSIONS

The available evidence suggests that terazosin improves urinary symptoms and flow measures associated with BPO. Effectiveness is superior to placebo or finasteride, similar to other alpha-blockers but less than TUMT. Adverse effects were generally mild but more frequent than other alpha-blockers and associated with between a two-to-four fold increase in treatment discontinuation.

Finasteride 1 mg has no inhibitory effect on omeprazole metabolism in extensive and poor metabolizers for CYP2C19 in Japanese

OBJECTIVE

To examine the inhibitory effect of finasteride 1 mg on the metabolism of omeprazole in genetically determined extensive (EMs) and poor metabolizers (PMs) for CYP2C19 in young healthy Japanese male subjects.

METHODS

Twenty-four volunteers participated in this study, among whom 12 were homozygous EMs and 12 were PMs for CYP2C19. A single center, controlled, randomized, open, crossover study with a 5 day washout between the two study periods was performed. Each of the six EMs and PMs received a single oral 20 mg dose of omeprazole on day 1 (treatment I). After a 5 day washout period, these subjects received 1 mg of finasteride once a day for three consecutive days, and a single oral 20 mg dose of omeprazole was co-administered on day 3 (treatment II). The 12 other EMs and PMs received treatments I and II in reverse. Plasma samples were collected for up to a 12 hours postdose of omeprazole, and the pharmacokinetic parameters of omeprazole were determined.

RESULTS

The geometric mean ratio (GMR) for the AUC((0-12 hr)) of omeprazole when co-administered with finasteride/omeprazole alone is 1.13 (90%CI, 1.03, 1.25) and 0.96 (0.88, 1.05) in EMs and PMs, respectively. Finasteride did not significantly alter C(max), T(max) and t(1/2) in both genotypes.

CONCLUSION

Finasteride 1 mg, widely used for the treatment of androgenetic alopecia in men, did not meaningfully increase omeprazole exposure (20 mg) in both EMs and PMs for CYP2C19. These results indicate that finasteride does not meaningfully inhibit CYP2C19 activity in vivo at the dose of 1 mg.

Terazosin for benign prostatic hyperplasia

BACKGROUND

Lower urinary tract symptoms associated with benign prostatic obstruction (BPO) occur in up to 70% of men over the age of 60 years. To relieve these bothersome symptoms, treatment options include alpha-antagonists, also know as alpha-blockers.

OBJECTIVES

We conducted a systematic review to evaluate the effectiveness and adverse effects of the alpha-blocker, terazosin, for treatment of urinary symptoms associated with BPO.

SEARCH STRATEGY

Trials were searched in computerized general and specialized databases (MEDLINE, Cochrane Library), by checking bibliographies, and by contacting manufacturers and researchers.

SELECTION CRITERIA

Studies were included if they (1) were randomized trials of at least 1 month duration, and (2) included men with symptomatic BPO and compared terazosin with placebo or active controls.

DATA COLLECTION AND ANALYSIS

Study, patient characteristics and outcomes data were extracted in duplicate onto standardized forms utilizing a prospectively developed protocol. The main outcome measure for comparing the effectiveness of terazosin with placebo or other BPO medications was change in urological symptoms as measured by validated symptom scores. Secondary outcomes included urodynamic measures. The main outcome measure for adverse effects was the number of men reporting side effects. We also evaluated the number of men withdrawing from treatment and the number withdrawing due to adverse effects.

MAIN RESULTS

17 studies involving 5,151 subjects met inclusion criteria (placebo-controlled (10); alpha-blockers (7); finasteride alone or in combination with terazosin as well as placebo (1); microwave therapy (TUMT) (1). Study duration ranged from 4-52 weeks. Mean age was 65 years and 82% of men were white. Baseline urologic symptom scale scores and flow rates demonstrated that men had moderate BPO. Efficacy outcomes were rarely reported in a fashion that allowed for data pooling but indicated that terazosin improved symptom scores and flow rates more than placebo or finasteride and similarly to other alpha antagonists. The pooled mean percentage improvements for the Boyarsky symptom score was 37% for terazosin versus 15% for placebo (n=4 studies). The mean percentage improvement for the American Urological Association symptom score (AUA) was 38% compared to 17% and 20% for placebo and finasteride, respectively (n = 2 studies). The pooled mean improvement in the International Prostate Symptom Score (IPSS) (40%) was similar to tamsulosin (43%). Peak urine flow rates improved greater with terazosin (22%), than placebo (11%) and finasteride (15%) but did not differ significantly from the other alpha-blockers. The percentage of men discontinuing terazosin was comparable to men receiving placebo and finasteride but was greater then with other alpha-antagonists. Adverse effects were greater than placebo and included dizziness, asthenia, headache and postural hypotension.

REVIEWER'S CONCLUSIONS

The available evidence suggests that terazosin improves urinary symptoms and flow measures associated with BPO. Effectiveness is superior to placebo or finasteride, similar to other alpha-blockers but less than TUMT. Adverse effects were generally mild but more frequent than other alpha-blockers and associated with between a two-four fold increase in treatment discontinuation.

Alpha-adrenergic blocking drugs in clinical medicine

The alpha-adrenergic blockers have played an important role in the treatment of vascular diseases. Nonselective alpha blockers have been used as treatments for patients with severe hypertension, including pheochromocytoma. Selective alpha 1 blockers have been used in the treatment of hypertension and prostatic obstruction, and these drugs have also been considered in the treatment of other vascular and nonvascular conditions. They have unique metabolic actions, specifically on plasma lipids and lipoproteins, which could be of clinical benefit.