Dutasteride, a prostate medicine

Your dermatologist mentioned it, or you read about it on a forum: dutasteride, described as a more powerful finasteride. You look up the leaflet and find a line that has nothing to do with hair: treatment of the symptoms of benign prostatic hyperplasia². So is it a hair loss medicine or not?

Both, depending on where you live and which doctor you ask. Here’s what regulators, studies and guidelines say, without dressing anything up.

What it is

Dutasteride belongs to the same family as finasteride: the 5-alpha-reductase inhibitors. This enzyme turns testosterone into DHT (dihydrotestosterone), the hormone that, in people predisposed by their genes, gradually shrinks the hair follicles on the scalp.

The difference is one of strength. The enzyme comes in several types. Finasteride mainly blocks type 2 and lowers DHT in the blood by about 65%. Dutasteride blocks types 1 and 2, and the drop reaches about 90%¹. How finasteride differs from minoxidil is covered in what sets the two medicines apart.

Licensed for the prostate, not for hair

In France, dutasteride is a prescription medicine licensed for one condition: benign prostatic hyperplasia, to treat its symptoms and reduce the risk of urinary retention and surgery². The European guideline on androgenetic alopecia points out that it has never been registered in Europe for hair loss¹.

Elsewhere, things differ. According to a 2024 review, only South Korea and Japan have approved it for male androgenetic alopecia³. In the United States, too, its approval covers the prostate only³.

A doctor can still prescribe it for hair loss: this is off-label prescribing. Spanish dermatologists ask doctors in that case to inform the patient, get their verbal or written consent and record it in their notes⁵.

What the studies show

The largest trial included 917 men aged 20 to 50. They were randomly given dutasteride at several doses, finasteride or a placebo for 24 weeks. At the dose used for the prostate, dutasteride increased hair count and hair thickness more than finasteride and placebo, both in a measured area of the scalp and on photos rated by a panel. The number and severity of side effects were similar across groups⁴.

These results have limits. The trial lasted six months, as the authors point out themselves, and several of them worked for the manufacturer⁴. The 2024 review reaches the same conclusion for the field as a whole: randomised trials of oral dutasteride don’t go beyond 24 weeks³. Yet androgenetic alopecia plays out over years.

Guidelines that disagree

Professional bodies read this evidence differently.

• The European S3 guideline ranks it second-line: it can be considered in men over 18 when finasteride hasn’t worked after 12 months¹.
• The Spanish Academy of Dermatology consensus ranks it first-line in men, for efficacy it considers greater and safety it considers similar, while noting that the use is off-label⁵.
• The British Association of Dermatologists writes that improvements beyond finasteride haven’t been convincingly shown, and that side effects have been reported to be more frequent and longer lasting⁶.

Three readings, one molecule. Choosing a treatment, or whether to take one at all, is done with a doctor who knows your history. To prepare for that appointment, the questions to ask your doctor can help.

Side effects

The French product information lists the effects seen in men treated for the prostate. In placebo-controlled trials, about 19% of the 2,167 patients on dutasteride had a side effect in the first year, mostly mild to moderate and mostly sexual².

Dutasteride product information, 2,167 men treated for an enlarged prostate. These men are older than most people losing their hair; the figures drop in the second year.²

The leaflet also lists breast tenderness or swelling (1.3%), loss or excess of body hair (uncommon) and, at an unknown frequency, depression, pain or swelling in the testicles and allergic reactions. It states that the sexual side effects may persist after stopping, and that dutasteride’s role in this is unknown². The medicine also lowers sperm count, volume and motility; reduced male fertility can’t be ruled out².

Any change in the breasts (a lump, nipple discharge) should be reported promptly, as should signs of depression².

Pregnancy, blood donation, blood tests

Dutasteride is contraindicated in women, children and adolescents². It is absorbed through the skin: women, children and adolescents should not touch a leaking capsule, and any contact should be washed off with soap and water. In a pregnant woman, it can disrupt the development of the genitals of a male foetus, especially in the first 16 weeks. It is also found in semen: the leaflet recommends a condom if your partner is or may become pregnant².

PSA, a blood test used to monitor the prostate, falls by about 50% after 6 months of treatment. A new baseline is then measured, and the doctor ordering the test needs to know. After stopping, PSA returns to its starting level within about 6 months².

For blood donation, the US label says not to give blood until at least 6 months after the last dose⁷. The medicine stays in the body for a long time: its half-life, the time for the amount in the blood to halve, is 3 to 5 weeks with continuous use². Mention it at the health check before you donate.

How long it takes, and stopping

Spanish dermatologists consider that a treatment for androgenetic alopecia should be kept up for at least 6 to 12 months before judging it⁵. The European guideline waits 12 months on finasteride before calling it a failure¹. That timeline is covered in when to judge finasteride.

On stopping, the rule applies to every treatment for pattern hair loss: they only work for as long as you take them⁶. And tablets aren’t the only route: minoxidil comes as a tablet or a lotion, with a different mechanism.

Tracking the effect with photos

With a treatment judged over months, the mirror is a poor witness. It changes with the light, the time of day, your haircut. You don’t remember exactly what your crown looked like six months ago.

Comparable photos solve that: same room, same light, same distance, dry hair, every week. Calvap guides you zone by zone, with your previous photo overlaid to match the framing. The journal keeps your treatment start date and what you notice, on the same timeline as your photos.

At your follow-up appointment, your doctor sees what has changed since day one, in pictures taken under the same conditions.