Drug reference

Finasteride

5-alpha-reductase inhibitor (type II) · Benign prostatic hyperplasia (BPH) agent, Androgenetic alopecia agent

Also known as Proscar, Propecia, Fincar, Finax

START

BPH: 5 mg OD; check baseline PSA (finasteride reduces PSA by ~50% after 6 months - multiply measured PSA by 2 for comparison). Alopecia: 1 mg OD; counsel on sexual side effects and need for 6+ months of use

TYPICAL MAX

5 mg/day (BPH); 1 mg/day (alopecia)

STOP IF

Severe depression/suicidal ideation, gynecomastia, significant sexual dysfunction, breast lumps

WATCH

PSA at 3 and 6 months (remember to double the value), IPSS score (BPH), hair growth/loss (alopecia), mood changes, sexual function, breast examination

CDSCO approvedJan AushadhiNPPA price-controlledATC G04CB01 (BPH); D11AX10 (alopecia)

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 23min · absorption onset
PEAK: 1.5h · Peak plasma concentration
t½: 6h · 5-6 hours (but tissue effect persists longer)
DURATION: 1d · 24-hour DHT suppression

EXCRETION

Renal (57%, metabolites); fecal (39%)

route + CYP

INTERACTIONS

1 major

incl. contraindicated

PREGNANCY

Contraindicated in pregnancy; teratogenic to male fetus (may cause feminization of external genitalia); women should not handle crushed tablets

FDA category + note

Top interactionssee all 2 →

PregnancyContraindicatedTextbookG&G 14e

Available in India

89 branded formulations and 86 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Jan Aushadhi — generic available at GoI pharmacies

Mechanism

Competitive inhibitor of 5-alpha-reductase type II enzyme, which converts testosterone to dihydrotestosterone (DHT) in prostate, hair follicles, and other tissues. Reduces DHT levels by ~70-80%, leading to prostate shrinkage (BPH) and prevention of further hair loss (androgenetic alopecia).

Indications

Benign prostatic hyperplasia (BPH) - improves symptoms and reduces risk of acute urinary retention and surgeryAndrogenetic alopecia (male pattern hair loss) - 1 mg dailyHirsutism in women (off-label, higher doses)Prevention of prostate cancer (controversial - 5 mg daily, REDUCE trial)

Dosing

Adult: BPH: 5 mg OD. Alopecia: 1 mg OD. May take with or without food
Pediatric: Not recommended under 18 years
Renal adjustment: No adjustment needed; not renally excreted
Hepatic adjustment: Use with caution in hepatic impairment; extensively metabolized in liver
Geriatric: Standard dosing for BPH (5 mg); no adjustment needed based on age
Max dose: 5 mg/day (BPH); 1 mg/day (alopecia)

Pharmacokinetics

Onset

BPH: 3-6 months for symptom improvement; PSA decreases by ~50% within 6 months. Alopecia: 3-6 months to see reduced hair loss; 12 months for regrowth

Peak effect

1-2 hours (Tmax)

Duration

24 hours

Half-life

5-6 hours (parent); but tissue effect persists much longer due to slow tissue dissociation

Bioavailability

~65%

Protein binding

90%

Metabolism

Hepatic CYP3A4 (extensive metabolism to inactive metabolites)

Excretion

Fecal (39%, as metabolites); renal (57%, as metabolites)

Contraindications

Hypersensitivity to finasteride
Pregnancy - women who are or may become pregnant should not handle crushed/broken tablets (teratogenicity risk to male fetus)
Not indicated for use in women or children

Side effects

Common

Decreased libidoErectile dysfunctionEjaculatory disorders (decreased volume)Gynecomastia / breast tendernessRash

Serious

High-grade prostate cancer (possible increased risk per REDUCE trial - controversial)
Male breast cancer (rare)
Depression / suicidal ideation (post-finasteride syndrome - rare but reported)
Sexual dysfunction persisting after discontinuation (post-finasteride syndrome)
Allergic reactions (angioedema, rash, pruritus)
Liver dysfunction