Dose of topical minoxidil

[asolof]

Many studies have been done comparing the relative efficacy, absorption, and side effects of different concentrations of topical minoxidil. They mostly document the superiority in efficacy of the 5% formulation over the lower concentrations tested, without a significant increase in side effects.

A Medline search failed to reveal any studies in which different volumes of the topical minoxidil were compared. The package insert says to apply 1 ml twice daily. I find this interesting because:

1. The instructions say to apply the 1ml over the affected area, regardless of the size of the affected area.

2. Since there is minimal absorption, any systemic effect of applying more to a smaller area is not likely to be increased.

3. Almost all other topical medicines require quantities proportional to the area being treated.

4. Different people have different amounts of existing hair onto which a variable amount of the application dose will be lost / wasted, depending on their quantity of hair and their application technique.

It seems to me that as long as a generous layer of the medicine can be spread over the affected scalp, anything more than that is superfluous. In my case I find that if I use the full 1 ml dose more of it tends to run, wet my hair, not get on the affected scalp, and my wet hair takes longer to dry. Cutting the dose down to 0.75ml seems to minimize these problems and still leave plenty to cover my scalp. It is a shame I couldn't find any studies where, say, different volumes of 5% minoxidil were compared on different size treatment areas so we would know for sure if the excess volume beyond what is necessary to cover the scalp, is really necessary.

 

[Bryan]

Many studies have been done comparing the relative efficacy, absorption, and side effects of different concentrations of topical minoxidil. They mostly document the superiority in efficacy of the 5% formulation over the lower concentrations tested, without a significant increase in side effects.

Interestingly, though, I can cite you an early study or two in which 2% topical minoxidil was compared to 3%, and oddly enough, the 2% was just about as good, or maybe even slightly better!

A Medline search failed to reveal any studies in which different volumes of the topical minoxidil were compared.

Actually, there was ONE study that tested multiple applications per day, like as many as 8 times per day! However, they didn't bother to look at haircounts, because that wasn't the purpose of the study. They were concerned with systemic absorption of topical minoxidil, and wanted to see if more minoxidil got into the bloodstream if you applied more and more of it to your skin. They found that the usual couple or so applications per day pretty much saturated the skin, so there was very little additional absorption with more frequent dosing.

2. Since there is minimal absorption, any systemic effect of applying more to a smaller area is not likely to be increased.

It's not really because of "minimal absorption", it's because of the saturation effect I discussed above.

It is a shame I couldn't find any studies where, say, different volumes of 5% minoxidil were compared on different size treatment areas so we would know for sure if the excess volume beyond what is necessary to cover the scalp, is really necessary.

My gut feeling is that a couple of 5% applications per day (or the equivalent amount of a 2% solution) onto a rather typically balding scalp is probably close to the limit of what you can achieve with topical minoxidil, at least with the standard ethanol/PPG vehicles.

Bryan