Oral vs topical minoxidil: what the head-to-head trials say

It is one of the most frequently asked questions in any hair loss consultation: if minoxidil comes as a tablet and as a liquid or foam to apply to the scalp, which works better? For a long time the answer relied on case series and on each dermatologist's experience. Since 2024 there has been something more solid: a randomised clinical trial comparing them head to head and a meta-analysis pooling the available trials. And the result, spoiler alert, is less spectacular than many expected.

What exactly the benchmark trial compared

The study published in JAMA Dermatology in 2024 by Penha and colleagues is the most cited because it did something almost nobody had done: randomise. Ninety men with androgenetic alopecia were assigned to oral minoxidil 5 mg a day or topical minoxidil 5% twice a day, in a double-blind, placebo-controlled design, for 24 weeks. In other words, neither the participants nor the assessors knew who was taking what, which reduces expectation bias, and in the hair field that bias is huge.

The authors' conclusion is explicit: low-dose oral minoxidil had similar efficacy to 5% topical minoxidil in men with androgenetic alopecia, and may be an option for patients who prefer the oral route or who do not tolerate topical treatment. Note the nuance: an alternative option, not a superior one. The study declared funding from the support fund of the Brazilian Society of Dermatology (FUNADERM) and is registered in the Brazilian Clinical Trials Registry under the identifier RBR-252w9r, two details that speak to methodological transparency.

The vertex finding: the only point where the oral form stood out

When the results are broken down by area, the only difference in favour of the oral form appears. The percentage increase in terminal hair density was greater in the oral group at the vertex, the crown: +27.1% (95% CI: 6.5–47.8; P=0.005). By contrast, on the frontal scalp the difference did not reach statistical significance (+13.1%; 95% CI: −11.5 to 37.5; P=0.15), nor did total hair density at the vertex (+2.1%; 95% CI: −8.1 to 12.3; P=0.27). And one more nuance: measured in hairs per square centimetre, which was the trial's primary outcome, the difference in terminal hair at the vertex (23.4 hairs/cm²; 95% CI: −0.3 to 43.0; P=0.09) did not reach significance.

This is worth reading calmly, because it is where the most exaggeration happens. The finding refers to one specific area and one specific parameter (terminal hair, the thick and pigmented kind), not to an overall advantage of oral over topical. And a confidence interval running from 6.5 to 47.8 signals considerable imprecision: the sample is small. That is why the authors themselves do not turn that figure into a recommendation of superiority.

The meta-analysis: four trials, 279 patients, no difference

The second pillar of evidence is a meta-analysis published in 2024 (PMID 39425514) that searched PubMed, Embase and Cochrane for randomised trials comparing oral minoxidil with the topical solution in androgenetic alopecia. It pooled 4 trials and 279 patients, with follow-up of between 24 and 39 weeks.

The two main efficacy outcomes showed no differences. For hair density, the standardised mean difference was 0.02 (95% CI: −0.25 to 0.29; P=0.88), with no heterogeneity between studies (I²=0%). For hair diameter, −0.25 (95% CI: −0.75 to 0.26; P=0.34; I²=36%). Put simply: adding up what has been published, neither route is found to outperform the other on the parameters that measure whether there is more hair and whether it is thicker. The consistency between studies (that I² of 0% for density) reinforces that this is not a draw caused by statistical noise, but a consistent draw.

Where there is a clear difference: hypertrichosis

There is an intuitive idea that taking a tablet avoids the hassle of putting something on your head every day. That is partly true in terms of convenience, but the meta-analysis dismantles the notion that the oral route comes at no cost: the incidence of hypertrichosis was significantly higher with oral than with topical minoxidil, with a relative risk of 2.01 (95% CI: 1.18–3.41; P=0.01; I²=0%). That is roughly twice as many cases of hair growth in places where it is not wanted (face, arms, back).

It makes sense: a medicine that circulates throughout the body acts on all follicles, not just those on the scalp. That is the price of the systemic route, and it is exactly the kind of information worth knowing beforehand rather than afterwards. If you want the full picture of what has been documented with the oral route, we break it down in the map of the real side effects of low-dose oral minoxidil.

What cannot be concluded from this evidence

Here is the uncomfortable part, and it is the part most often left out of thirty-second videos. The available randomised comparative evidence is limited to time frames of 24 to 39 weeks and to small samples of men: 90 patients in the JAMA Dermatology trial, 279 in the meta-analysis. With those numbers and that length of time:

• It cannot be claimed that either route is equivalent or safe in the long term. Six months or a little more is not the time frame of a treatment that is usually considered over years.
• The results cannot be extrapolated to women: the verified trials were carried out in men with androgenetic alopecia.
• The favourable vertex finding cannot be turned into an overall advantage for the oral form: it was one specific area and a single parameter.
• It cannot simply be said that the oral form works better. What the evidence supports is similar efficacy, with a side-effect profile that differs.

There is also a prior condition that no comparison of routes can resolve: the diagnosis has to be right. Minoxidil is studied here in androgenetic alopecia, the patterned hair loss that progresses gradually, and that condition is not the only one that causes hair loss. Sudden, diffuse shedding after childbirth, surgery or an illness usually corresponds to telogen effluvium, which tends to resolve on its own, and round, well-defined patches point to alopecia areata, which has an autoimmune mechanism and a different approach. Comparing routes of administration when the diagnosis is wrong is like arguing about the colour of the car before knowing whether it has an engine.

In summary, and what you can do with this

What to remember is simple: when compared head to head, oral and topical minoxidil perform similarly in men at 24–39 weeks, with a slight edge for the oral form at the vertex and twice as much hypertrichosis with the systemic route. The choice, therefore, is not made in an article, but according to each person's diagnosis, preferences and risk profile. That is what medical hair loss treatment by telemedicine exists for in Spain today, with a prior assessment, a prescription when appropriate from a registered doctor and ongoing follow-up, which is what AiON offers. If you want to start at the beginning, you can check whether you are eligible in a few minutes.