One of the most effective male pattern hair loss treatments of the last 3 decades is Propecia, often known by its generic name finasteride. Finasteride is an oral medication designed to target the mechanism of male pattern hair loss at a chemical level, without the need for any messy creams or topical treatments, dubious devices or gimmicks, or any kind of hair replacement surgery.
Despite working systemically and altering certain hormone levels, finasteride is generally quite safe, with few side effects. However, like any medication you take orally, there can be some finasteride interactions and contraindications that you should be aware of, which may mean finasteride is not the best choice for you as an individual.
In this guide, we’ll explore the finasteride interactions and contraindications information, highlighting those conditions, medications, and other factors that might justify not choosing finasteride for your hair loss treatment. The information is based on both clinical trials and independent studies and features conclusions from the sum total of information presented to the FDA on adverse drug interactions and side effects over the course of the nearly three decades that finasteride has been on the market.
This shows that, for most men seeking hair loss treatment, finasteride is safe and effective – and outlines the precautions for finasteride interactions, contraindications, and those who should not use finasteride.
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General Disclaimer
As with all medical articles featured on Invigor Medical, this information is accurate and current to the best of our knowledge but is not a substitute for reviewing the official prescribing information. It is also not a replacement for consulting your doctor about the risks and benefits of finasteride.
Always discuss your medical history, health conditions, and all prescription or OTC medications and supplements with your provider before beginning treatment.
The Basics Of Finasteride
Finasteride is usually supplied as a 1 mg tablet taken once daily, with or without food. This is the standard dose for androgenic alopecia (male pattern baldness). Finasteride inhibits 5-alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT). Lowering DHT helps reduce hair loss and can support regrowth.
Finasteride Interactions
Finasteride is generally safe for long-term use. Sexual side effects occur in approximately 2.1%–3.8% of users—most commonly erectile dysfunction, decreased libido, or ejaculatory dysfunction. Additional adverse events reported include depression and breast tenderness.
Regarding prostate cancer risk, it is important to use accurate terminology.
5-alpha-reductase inhibitors have been associated with a higher incidence of high-grade prostate cancer in some trials; however, causality has not been established, and the clinical significance for the 1 mg dose used for hair loss remains uncertain.
This phrasing aligns with FDA labeling and is more medically precise than stating “known to cause.”
Aside from side effects, finasteride interactions may relate to how it is metabolized and eliminated—but overall, meaningful drug-drug interactions are rare.
No Known Finasteride Interactions
Clinical testing has shown no meaningful interactions between finasteride and medications metabolized through the cytochrome P450 pathway.
No significant interactions were observed with:
- Antipyrine
- Digoxin
- Propranolol
- Theophylline
- Warfarin
Additional medications studied without evidence of interaction include:
- Acetaminophen
- Aspirin
- Alpha-blockers
- Analgesics
- ACE inhibitors
- Anticonvulsants
- Benzodiazepines
- Beta-blockers
- Calcium channel blockers
- Cardiac nitrates
- Diuretics
- H2 antagonists
- HMG-CoA reductase inhibitors
- NSAIDs
- Quinolone antibiotics
Specific Finasteride Interactions, Adverse Events, And Precautions
Known prohibitions and precautions include:
- Women: Finasteride is not suitable or approved for use in women.
- Pregnancy: Finasteride should not be used by or handled by women who are pregnant or may become pregnant, as it can affect the development of male fetuses.
- Breastfeeding: Avoid all use and handling.
- Children: Not approved for pediatric use.
- Elderly men: No age-based contraindication, though efficacy may be reduced.
- Hepatic impairment: Use with caution in patients with liver disease. The effect of hepatic impairment on finasteride pharmacokinetics has not been studied, and no specific dose adjustment has been defined.
Finasteride Contraindications
Formal contraindications include:
- Use in women who are pregnant or may become pregnant
- Known hypersensitivity to finasteride or product components
- Men with current or prior prostate cancer should consult a physician regarding risk–benefit specifics
- Finasteride has been associated with a higher incidence of high-grade prostate cancer in some studies, but causation has not been established, particularly at the 1 mg dose for hair loss
Other Considerations For Finasteride Interactions, Cautions, And Side Effects
The full range of finasteride interactions, cautions, contraindications, warnings, side effects, and similar information should be reviewed with your doctor or prescriber prior to starting a finasteride treatment regimen. Every individual is unique, and a small portion of individuals may experience atypical symptoms, interactions, or responses to finasteride, as with any medication. For more information, you can review the complete US prescribing information for brand-name Propecia, on file with the US Food and Drug Administration.
Concluding Thoughts
While finasteride is generally considered safe and is highly effective at stopping male pattern hair loss and even regrowing hair, proper precautions need to be taken before and during the use of the drug.
Certain populations should avoid finasteride, as we outlined in our guide. Finasteride interactions are fortunately few, and mostly relate to prohibited populations (women, pregnant women, children), and those with physical impairments (such as hepatic impairment) that can interfere with metabolism and elimination of the drug.
Generally speaking, there are no serious finasteride interactions with a range of medications tested during pre-marketing of the drug, nor adverse finasteride interactions that have come to light over nearly 30 years of use by millions of people. For most men, it’s an affordable, effective, and safe way to reverse the effects of male pattern hair loss. Those interested can buy finasteride easily online with a prescription.
