Minoxidil Absoption Paper And Puzzling Real Life Experience

[mvalley]

I came upon this paper which shows how much topical minoxidil is absorbed systemically. They did it via C14 labeling so it should be highly accurate. The absorption was 2.4mg-5.4mg/day. My question is why don't we see more edema related side effects with that kind of absorption? Meaning that using it topically would be like taking an oral dose of ~5mg/day.

Percutaneous Absorption of Minoxidil in Man
https://jamanetwork.com/journals/jamadermatology/article-abstract/545803


A related concept is how GOOD the results are with just 5mg daily of oral minoxidil --
Effectiveness and Safety of Low-Dose Oral Minoxidil in Male Androgenetic Alopecia
https://www.jaad.org/article/S0190-9622(19)30685-1/fulltext

 

[mvalley]

Another reference: https://www.glowm.com/resources/glowm/cd/pages/drugs/m053.html

Absorption: Poorly absorbed through intact skin. About 0.3% to 4.5% of a topically applied dose reaches the systemic circulation. Application to skin with decreased integrity may increase systemic absorption.

So if you are using 5% minoxidil twice per day, that's 100mg of minoxidil that is going on your head. That means you would be getting 0.3mg to 4.5mg/day. It's interesting since it implies many folks are getting the equiv of a low oral dose, daily.