Finasteride

# Finasteride ## Overview - **Classification**: 5-alpha reductase inhibitor - **Mechanism**: Inhibits Type II 5-alpha reductase, blocking conversion of testosterone to dihydrotestosterone (DHT), which reduces prostate size and increases hair growth. ## Primary Indications 1. **Benign Prostatic Hyperplasia (BPH)** - Treatment of symptomatic BPH to improve symptoms, reduce risk of acute urinary retention, and reduce need for surgery. 2. **Androgenetic Alopecia (Male Pattern Hair Loss)** - Treatment of male pattern hair loss in men (vertex and anterior mid-scalp). ## Adult Dosing ### Standard Dosing **Benign Prostatic Hyperplasia (BPH)** - **Dose**: **5 mg** - **Frequency**: Once daily - **Route**: Oral - **Duration**: Long-term **Androgenetic Alopecia (Male Pattern Hair Loss)** - **Dose**: **1 mg** - **Frequency**: Once daily - **Route**: Oral - **Duration**: Long-term, at least 3-6 months to assess efficacy. ### Dose Adjustments - **Renal Impairment**: No dose adjustment needed. - **Hepatic Impairment**: No specific dose adjustment recommended. Use with caution in severe hepatic impairment. - **Elderly Patients**: No dose adjustment needed. ## Pediatric Dosing ### Neonates (0-28 days) - **Finasteride is NOT indicated for pediatric use.** - **Special Notes**: Contraindicated in children. Exposure may cause abnormal development of male external genitalia. ### Infants (1-12 months) - **Finasteride is NOT indicated for pediatric use.** - **Special Notes**: Contraindicated in children. Exposure may cause abnormal development of male external genitalia. ### Children (1-12 years) - **Finasteride is NOT indicated for pediatric use.** - **Special Notes**: Contraindicated in children. Exposure may cause abnormal development of male external genitalia. ### Adolescents (13-18 years) - **Finasteride is NOT indicated for pediatric use.** - **Special Notes**: Contraindicated in children. ## Safety Information ### Contraindications - **Absolute**: Pregnancy (Category X) - risk of teratogenicity in male fetus. - **Absolute**: Hypersensitivity to finasteride or any component of the product. - **Absolute**: Not for use in women or children. ### Common Adverse Effects - **Common (1-10%)**: Decreased libido, erectile dysfunction, ejaculatory dysfunction (e.g., decreased ejaculate volume). - **Common (1-10%)**: Breast tenderness and enlargement (gynecomastia). - **Common (1-10%)**: Depression. - **Serious but Rare**: Male breast cancer, high-grade prostate cancer (potential masking due to PSA reduction), hypersensitivity reactions (e.g., angioedema). ### Key Drug Interactions - **None Significant**: Finasteride does not significantly interact with the cytochrome P450 system. - **Prostate-Specific Antigen (PSA)**: Finasteride decreases serum PSA levels by ~50%. This must be accounted for when interpreting PSA results. ## Monitoring & Follow-up - **Before Treatment**: Baseline prostate-specific antigen (PSA) levels and digital rectal exam (DRE) for BPH patients. - **During Treatment**: Periodic PSA monitoring. PSA levels should be doubled for interpretation while on finasteride. - **Clinical Signs**: Monitor for sexual side effects, breast changes (tenderness, lumps), and mood changes. ## Clinical Pearls - 💡 **Pregnancy Risk**: Pregnant women or those who may become pregnant should **NOT handle crushed or broken finasteride tablets** due to risk of absorption and potential harm to male fetus. - 💡 **PSA Interpretation**: Finasteride reduces PSA levels by approx. 50%. This should be accounted for when evaluating PSA values for prostate cancer screening. - 💡 **Onset of Effect**: For hair loss, expect to see effects after **3-6 months** of daily use. For BPH, symptom improvement may take **6-12 months**. - 💡 **Consistency**: Take **once daily** consistently. Missing doses can reduce efficacy, especially for hair loss. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.