Minoxidil : Excretion and Metabolism

[jellybean_gurlz]

Hi there. I have been reading quite a lot of posts on this site but there was a particular one which really sparked my interest. Especially since it is heavily connected with the Minoxidil,which I am especially curious about,as a 1st-year medical student myself. I heard its usage is deemed to be controversial in some cases


The title of the thread is "Blood donation - Are the medications I use safe?" by capati92, under the Blood Disorders Community and the original poster mentioned something about using 5% Minoxidil topical solution though she is a female (based on my prior medical knowledge, only 2% is recommended for women as with a higher dose,it is highly likely that they will gain unwanted facial hair and what not). And true enough,this 20 year-old girl, not much older than myself at 19-going-on-20, has that problem.


The main question I have regarding Minoxidil is, can it be absorbed systematically in topical solution form so much so that it could trigger such an effect? If so,after how long is Minoxidil excreted from the body? What is its half-life and what is its duration for metabolism? Thank you. :)

[Cody Midlam, PharmD]

From the available data, there does appear to be a dose-dependent correlation with hypertrichosis (facial hair growth) in women when using the 2% or 5% minoxidil solution. One study comparing minoxidil 2 vs 5% found 4 out of 153 patients receiving the 5% solution developed facial hair. In all four of these patients, serum minoxidil was found to be low or non-detectable. The correlation between increased facial hair growth with the 5% solution is evident, but the cause is undetermined. The adverse effect of facial hair growth is reversible and may disappear despite continued use of the product.

Regarding the systemic absorption of topical minoxidil and its excretion; percutaneous absorption of 2% minoxidil is reported to be 0.3- 4.5% of the applied dose on average. In comparison to the oral form of minoxidil, peak serum concentrations of minoxidil 5mg daily are generally 20-30 times higher than the mean serum concentrations achieved after twice daily minoxidil 2% when applied topically. Percutaneous absorption may be effected by alteration to the scalp such as irritation.

Following topical administration of minoxidil, systemically absorbed minoxidil is excreted primarily in the urine, and following cessation of topical minoxidil dosing, 95% of the systemically absorbed drug is eliminated within 4 days. One study finds the mean plasma half-life of minoxidil and its metabolites is 4.2 hours.

[jellybean_gurlz]

Hi there. Thank you so much for the enlightening evidences. This has helped me so much and it really means a lot to me. :) Again,I'm truly grateful for all the trouble and effort you have put in to find this for me.