Finasteride Tablets: Uses and Dosages
Finasteride tablets are primarily indicated for the treatment of benign prostatic hyperplasia (BPH) at a dose of 5 mg once daily, and for male androgenetic alopecia (male pattern baldness) at a dose of 1 mg once daily. 1, 2, 3
Indications and Dosing
For Benign Prostatic Hyperplasia (BPH):
- Dosage: 5 mg tablet taken once daily with or without meals 3
- Mechanism: Inhibits 5-alpha-reductase, reducing dihydrotestosterone (DHT) levels, which leads to:
- 20-30% reduction in prostate volume after 6-12 months
- 67% reduction in risk of acute urinary retention
- 64% reduction in need for BPH-related surgery 2
- Efficacy: Maximum efficacy typically achieved after 12 months of continuous therapy 2
For Male Pattern Hair Loss (Androgenetic Alopecia):
- Dosage: 1 mg tablet taken once daily 4, 5
- Mechanism: Inhibits conversion of testosterone to DHT in scalp, resulting in:
Combination Therapy
- For BPH: Finasteride 5 mg once daily can be combined with alpha-blockers (e.g., doxazosin) for enhanced efficacy 2, 3
- Evidence: Combination therapy with alpha-blockers and 5-ARIs is the most effective medical therapy for men with moderate-to-severe lower urinary tract symptoms (LUTS) and enlarged prostates 2
Important Clinical Considerations
Patient Selection:
- For BPH: Most effective in men with enlarged prostates (>40 mL)
- Not appropriate for men with LUTS who do not have prostatic enlargement 1
Monitoring:
- PSA levels: Values should be doubled for prostate cancer screening in patients on 5-ARIs
- Treatment response: Should be assessed after 4-12 weeks, with maximum benefit at 12 months 2
- Duration: Long-term therapy is required to maintain benefits
Common Adverse Effects:
- Sexual dysfunction (typically reversible):
- Gynecomastia 4
Common Pitfalls to Avoid:
- Prescribing for small prostates where efficacy is limited
- Expecting rapid symptom improvement (takes months to achieve significant effects)
- Discontinuing therapy too early before maximum benefit is achieved
- Not adjusting PSA values (approximately 50% reduction after 12 months) when screening for prostate cancer 2
Pharmacokinetics:
- Absorption: Well absorbed orally with 63% bioavailability
- Peak concentration: 1-2 hours after administration
- Protein binding: Approximately 90%
- Half-life: 6-8 hours
- Metabolism: Produces five metabolites, two with minimal activity 8
Finasteride has demonstrated a favorable safety profile with minimal clinically relevant drug interactions, and overdose appears to have limited consequences, with doses up to 80 mg/day for 3 months reported without adverse effects 3, 8.