Finasteride, minoxidil, dutasteride and PRP: what the research shows

Four treatments for pattern hair loss have real human trials behind them: finasteride, dutasteride, minoxidil and PRP. Ketoconazole shampoo has smaller studies. Stem cells and exosomes are promising but still experimental. This guide explains what each one does, what the research shows and what the side effects are. It is not a prescription: a doctor who knows your health decides what suits you.

At a glance

“Off-label” means a doctor prescribes a medicine for a use it is not officially licensed for, based on research. It is common in hair medicine, and the prescribing doctor takes responsibility for the choice.

How hair loss medicines work

Pattern hair loss is driven mostly by DHT, a hormone made from testosterone. In people whose hair follicles are sensitive to it, DHT slowly shrinks the follicles until they make only thin, short hairs, and then none. More than 380 genetic regions are linked to it, which is why it runs in families (Liu 2025).

• Finasteride and dutasteride lower DHT, which slows or stops the shrinking.
• Minoxidil does not act on hormones. It stimulates the follicles to grow, although exactly how is still not fully understood.
• PRP and ketoconazole may support growth through growth factors and by calming scalp inflammation. The evidence for them is weaker.

Medicines work on the hair you still have. They cannot bring back hair where the follicles are gone. That is where a hair transplant helps.

Finasteride

In short: finasteride is the best-studied medicine for male pattern hair loss. In large trials it slowed hair loss and regrew some hair. A minority of men get sexual or mood side effects.

What the trials show:

• In two one-year trials of 1,553 men aged 18 to 41, finasteride improved scalp hair at one and two years, while men on placebo kept losing hair. Side effects were uncommon in these trials (Kaufman 1998).
• A 2022 analysis of 23 trials ranked finasteride among the most effective treatments for men at 48 weeks (Gupta 2022).
• A spray version for the scalp regrew hair about as well as the tablet in a trial of 458 men, with blood levels of the drug more than 100 times lower (Piraccini 2022).

Side effects:

• Pooled placebo-controlled trials still show a higher risk of sexual side effects, such as lower libido or erection problems: about 1.7 times the risk with placebo (Lee 2019).
• Reviews also link finasteride to a higher rate of depression. A small number of men report sexual or mood symptoms that continue after stopping, known as post-finasteride syndrome. Depression was added to the US label in 2011 (Pompili 2021, Gupta 2022 review).

Who it is not for: finasteride is licensed for men. In women it is off-label. A Cochrane review found it no better than placebo for female pattern hair loss, and experts consider it only after the menopause (van Zuuren 2016, Gupta 2025).

Dutasteride

In short: dutasteride lowers DHT more than finasteride and regrew more hair in trials. For hair loss it is prescribed off-label, usually when finasteride has not worked well enough.

• In a trial of 917 men over 24 weeks, dutasteride increased hair count and hair thickness more than both finasteride and placebo, with similar side effects (Gubelin Harcha 2014).
• The 2022 analysis of 23 trials found the largest rise in total hair count at 24 weeks with dutasteride (Gupta 2022).
• Experts suggest topical minoxidil and finasteride first, and dutasteride if those are not enough. Dutasteride can lower sperm count and movement, so it needs care in men with fertility concerns, and men whose partner is pregnant should avoid it (Gupta 2025).
• In pooled trials the rise in sexual side effects was not statistically significant, but there were few dutasteride trials (Lee 2019).
• Dutasteride injected into the scalp (mesotherapy) is being studied. Results are encouraging, but methods are not standardised and side effects have been reported (Gupta 2023).

Minoxidil

In short: minoxidil on the scalp is the best-studied treatment for both men and women. A low-dose tablet is a newer, off-label option that some people find easier to keep up.

On the scalp:

• In 393 men over 48 weeks, the stronger solution regrew 45% more hair than the weaker one, and more than placebo. It also caused more itching and irritation (Olsen 2002).
• In 381 women over 48 weeks, the stronger solution beat placebo on every main measure. Side effects included itching, irritation and unwanted facial hair (Lucky 2004).
• A Cochrane review of 47 trials in women found evidence that topical minoxidil works and is safe for female pattern hair loss (van Zuuren 2016).

As a low-dose tablet:

• In a trial of 90 men over 24 weeks, the tablet was not better overall than the solution, although photos favoured it on the crown (Penha 2024).
• In 1,404 patients, the most common side effect was unwanted hair growth on the face or body (15%). Light-headedness, fluid retention and a fast heartbeat each affected fewer than 2 in 100, and no life-threatening effects were seen (Vañó-Galván 2021).
• In 2025, 43 hair specialists from 12 countries agreed on how the tablet should be started, who should not take it and how it should be monitored (Akiska 2025).

If you use minoxidil on your scalp and are planning a transplant, your surgeon tells you when to stop it before surgery and when to restart.

PRP

In short: PRP (platelet-rich plasma) is made from a small sample of your own blood, concentrated and injected into the scalp. Randomised trials show it increases hair density. They are small and use different methods, so the certainty is moderate rather than strong.

• In nine randomised trials with 238 patients, PRP increased hair density at 3 and 6 months compared with placebo, but not hair count or thickness (Zhang 2023).
• Five trials compared PRP plus minoxidil with minoxidil alone. Adding PRP improved hair density, but the certainty of the evidence was low to very low (Yao 2024).
• A 2025 Canadian expert consensus included PRP among the treatments it recommends (Landells 2025).

Our PRP page explains how we use it.

Ketoconazole shampoo

In short: ketoconazole is a medicated anti-dandruff shampoo. Small studies suggest it may help as an add-on to other treatment, but there are no large trials yet.

• It acts against scalp yeast and calms inflammation, which may play a part in pattern hair loss. In an early study the shampoo improved hair density and hair size about as much as a minoxidil routine, and the authors called for larger controlled trials (Piérard-Franchimont 1998).
• A 2020 review of five human studies with 318 people found thicker hairs and better photos, and called it a promising add-on. Randomised trials are still needed (Fields 2020).
• The 2025 Canadian consensus came close to recommending it as part of a routine (Landells 2025).

Stem cells and exosomes: promising, not proven

In short: these are among the most talked-about new treatments. Early studies are encouraging: in small trials some patients had more hair density (Krefft-Trzciniecka 2023; Chien 2024). But the trials are small, products and methods differ, and long-term effects are not known. Nobody can promise they work for everyone.

• A 2023 review of 14 studies found stem cell treatments promising, with no major side effects reported, but said the results must be repeated in larger groups before they can be relied on (Krefft-Trzciniecka 2023).
• Ten trials of stem cell “conditioned medium” (the fluid stem cells are grown in) showed higher hair density, but only three of them were randomised (Chien 2024).
• Exosomes, tiny packages released by cells, have been tested in 125 patients with hair loss across nine studies. Side effects were rare in these studies. Across skin medicine as a whole, at least ten serious adverse events have been reported, and products are not yet made to consistent standards (Queen 2025).

What recent expert guidance does not recommend

A 2025 Canadian expert consensus reviewed 45 hair loss treatments. Among those it did not recommend were rosemary oil, caffeine products and herbal lotions (Landells 2025). Popular does not mean proven.

Medicines and a hair transplant

In short: transplanted hair comes from the back of the head, where hair resists DHT, so it usually does not need medicine. Your own hair around it can keep thinning, and that is the hair medicines protect.

• In a randomised trial of 79 men, finasteride taken from 4 weeks before to 48 weeks after a transplant improved the hair around the transplanted area. Visible improvement was seen in 94% of men on finasteride and 67% on placebo (Leavitt 2005).
• Over the years, thinning behind a new hairline can leave gaps. Our surgeons often see second procedures that became necessary because a patient’s own hair kept thinning after they stopped their medicine.
• Your surgeon may discuss medication such as finasteride or minoxidil, and its possible side effects. The choice is yours. Do not start or stop any medicine without advice from a doctor.

This guide explains published research. It is not medical advice or a prescription. Hair loss medicines can have side effects, and some are not suitable in pregnancy or with certain health conditions. For more papers our surgeons are reading, see New research we’re reading.

Sources

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