Minoxidil is a well-known drug to regrow lost hair. Some men also use it in an attempt to grow a beard.
But how long does it take for minoxidil to clear out of our system? What is the half life of minoxidil? And more particularly, what is the half life of topical minoxidil, since a lot of people will be applying it for hair growth or beard growth.
I’ve researched what science deems to acknowledge as the average minoxidil half life. And thus, without further ado, let us deep dive into the clearance of minoxidil.
Minoxidil half life
Topical minoxidil half life
The half-life of topical minoxidil averaged 22 hours, compared to 1.49 hours for the oral formulation. Minoxidil and its metabolites are excreted almost entirely in the urine (97%), with a very minor degree of elimination via the faeces (3%).
Renal clearance of minoxidil and minoxidil glucuronide calculated from oral data averaged 261 mL/min and 290 mL/min, respectively.
Following cessation of dosing, approximately 95% of topically applied minoxidil will be eliminated within four days.[1]https://www.medicines.org.uk/emc/product/5082/smpc
Another study suggests that oral minoxidil reaches its peak plasma levels in about 1 hour. It suggests that the half-life of minoxidil is about 2.77-4.2 hours. [2]https://pubchem.ncbi.nlm.nih.gov/compound/4201#section=ATC-Code
It should be noted that the topical minoxidil solution is poorly absorbed through the skin (percutaneous absorption) with an average <2% of the applied dose.[3]https://www.sciencedirect.com/topics/chemistry/minoxidil
Since we are talking about using topical minoxidil for beard growth, the average half-life of topical minoxidil on the face will be about 22 hours.[4]https://www.medicines.org.uk/emc/product/5082/smpc
Bernstein’s medical center, which is specialized in hair restoration also suggests that topical minoxidil has a half-life of 22 hours in the skin[5]https://www.bernsteinmedical.com/medical-treatment/rogaine-minoxidil/
Even though it has a half-life of about 22 hours, it should be noted that Johnson & Johnson, which is the company that makes Rogaine specifically states that topical minoxidil is less efficacious if it is only applied topically once a day. It should also be mentioned that there is only a small amount of systematic absorption when the minoxidil is applied topically.
If you are wondering, this is how you should apply minoxidil.
Oral minoxidil half life
As noted in the studies above, the half life of oral minoxidil is about 1.49 hours. Another study said that the oral minoxidil half life is between 2.77 and 4.2 hours.
Conclusion
Minoxidil’s half life is different for the oral formula and topical solution. The half life of minoxidil in regard to the topical formula is much longer when compared to the oral minoxidil’s half life.
This can possibly be attributed due to the larger/faster amount of systematic absorption and, thus, clearance of the oral minoxidil solution when compared to the topical formula. That’s important to understand since we know that minoxidil can interact with other drugs.