5-alpha-reductase inhibitor (type II)
Finasteride drug interactions: a practical overview
Drug interactions are the single biggest cause of preventable medication problems. Finasteride (Finasteride) interacts to varying degrees with several classes of medication and with a smaller list of foods. This page summarises the practically important ones at 1mg, framed for a real-world prescription review rather than an exhaustive PDF list.
High-priority interactions for Finasteride
For Finasteride, the most clinically relevant interactions are typically with strong CYP3A4 inhibitors and inducers, with cardiovascular medications (notably nitrates for several 5-alpha-reductase inhibitor (type II) agents), with central nervous system depressants, and with medications affecting blood pressure or heart rate. Finasteride binds with high affinity to 5-alpha-reductase type II, blocking the conversion of testosterone into DHT.
Working with the pharmacist
A pharmacist review of all current medications is the practical safeguard against unintended interactions with Finasteride. According to the prescribing information for Finasteride, the full medication list — prescription, OTC, supplements and recreational substances — should be reviewed before starting and at every dose change at 1mg.
Frequently asked questions
What's the most important Finasteride interaction to know? ▾
For most 5-alpha-reductase inhibitor (type II) medications, the highest-priority interaction is with nitrate medications used for chest pain — this combination is often a hard contraindication. After that, strong CYP3A4 inhibitors (some antifungals, macrolides) are the next concern at routine 1mg doses.
Do I need to tell the pharmacist about supplements? ▾
Yes. Supplements and herbal products can interact with Finasteride in ways that prescription drug-drug interaction databases miss. The pharmacist needs the complete picture — including supplements like St John's Wort, grapefruit-containing products and high-dose vitamins — to flag risks at 1mg.
Products containing Finasteride
More on Finasteride
- With alcoholFinasteride and alcohol — is it safe to drink?
- With foodShould Finasteride be taken with food?
- Side effectsFinasteride side effects: common, rare and warning signs
- Dosage guideFinasteride dosage guide: how much to take and when
- OnsetHow fast does Finasteride start working?
- DurationHow long does Finasteride last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.