Formulary
Finasteride: Indications, Dosing, Side Effects and Interactions
A specific inhibitor of the enzyme 5-reductase, which metabolises testosterone into the more potent androgen, dihydrotestosterone.
MedNext Academy | 3 min read
Finasteride: Indications, Dosing, Side Effects and Interactions
A specific inhibitor of the enzyme 5-reductase, which metabolises testosterone into the more potent androgen, dihydrotestosterone.
Drug action
A specific inhibitor of the enzyme 5-reductase, which metabolises testosterone into the more potent androgen, dihydrotestosterone.
Indications and dose
**Benign prostatic hyperplasia**
- **Adult** (By Mouth): 5 mg once daily, review treatment at 3-6 months and then every 6-12 months (may require several months treatment before benefit is obtained).
**Androgenetic alopecia in men**
- **Adult** (By Mouth): 1 mg once daily, continuous use for 3-6 months is required before benefit is seen, and effects are reversed 6-12 months after treatment is discontinued.
Cautions
Obstructive uropathy
Side effects
Common or very common Sexual dysfunction Uncommon Breast abnormalities; depression; skin reactions Frequency not known Angioedema; infertility male; palpitations; suicidal behaviours; testicular pain
Interactions
**Other interactions (4):**
- Finasteride is metabolised primarily via, but does not affect, the P450-3A4 system.
- Although the risk of finasteride to affect the pharmacokinetics of other drugs is estimated to be small, it is probable that inhibitors and inducers of cytochrome P450 3A4 will affect the plasma...
- Compounds which have been tested in man have included antipyrine, digoxin, glibenclamide, propranolol, theophylline and warfarin and no interactions were found.
- Due to lacking data for the concomitant use of finasteride and topical minoxidil in male pattern hair loss the combination is not recommended.
Medicinal forms
Suspension
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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