Hair Loss

Key takeaways

• Hair loss medicines work through two separate mechanisms: minoxidil widens scalp blood vessels to stimulate follicles, while finasteride and dutasteride block the hormone that shrinks them.
• Minoxidil is a topical liquid or foam applied to the scalp; finasteride and dutasteride are oral tablets.
• Expect 3 to 6 months of regular use before you notice a difference, and up to a year for the full effect; results reverse within months of stopping.
• Finasteride and dutasteride are teratogenic: women who are or may become pregnant must not handle broken or crushed tablets, since the drug can absorb through skin and harm a male fetus.

How hair loss medicines work

Minoxidil widens blood vessels in the scalp and is thought to prolong the growth phase of hair follicles, though the exact mechanism isn't fully established. Finasteride and dutasteride block the enzyme that converts testosterone into dihydrotestosterone (DHT), the hormone most responsible for shrinking scalp follicles in male pattern hair loss. Neither approach restores follicles that have already stopped producing hair entirely.

Choosing between minoxidil, finasteride and dutasteride

• Minoxidil: applied to the scalp once or twice daily as a liquid or foam. Some shedding in the first few weeks is normal and doesn't mean it's failing. It doesn't work through hormones, so both men and women use it.
• Finasteride: a daily oral tablet that blocks the enzyme that produces DHT, slowing hair loss in men. It can lower libido or cause erectile difficulty in a small proportion of users, effects that usually reverse on stopping. It is teratogenic: women who are or may become pregnant must not handle broken or crushed tablets, since the active ingredient absorbs through skin and can affect a developing male fetus.
• Dutasteride: works the same way as finasteride but blocks both forms of the enzyme, producing a larger drop in DHT. It carries the same pregnancy handling warning as finasteride, and its longer half-life means it stays in the body for weeks after you stop.

Common questions

How soon will I see results?

Most users need 3 to 6 months of continuous use before new growth becomes visible, and up to a year for the full effect. Stopping treatment lets hair loss resume within months, since neither drug produces a lasting change once you come off it.

Can women use these medicines?

Minoxidil is used by both men and women for pattern hair loss. Finasteride and dutasteride are not used by women who are or may become pregnant, because of the risk to a male fetus, and women handling these tablets for a partner should still avoid contact with any that are broken or crushed.

Do these medicines regrow hair permanently?

No. The effect lasts only as long as you keep using the medicine, and follicles that have already scarred over won't respond to any of these treatments.

Safety essentials

• Finasteride and dutasteride are teratogenic: women who are or may become pregnant must not handle broken or crushed tablets.
• Tell your prescriber about liver disease before starting finasteride or dutasteride, and about scalp irritation or heart problems before starting minoxidil.
• Persistent sexual side effects, mood changes, or breast tenderness or enlargement while on finasteride or dutasteride need a doctor's review rather than stopping and restarting on your own.
• Stopping either drug reverses its benefit within months; hair lost while off treatment doesn't automatically return once you restart.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.