What is the mechanism of action for minoxidil in the treatment of alopecia areata?

Updated: Aug 06, 2020
  • Author: Chantal Bolduc, MD, FRCPC; Chief Editor: Dirk M Elston, MD  more...
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The exact mechanism of action of minoxidil remains unclear. Minoxidil does not appear to have either a hormonal or an immunosuppressant effect. Minoxidil most likely has a direct mitogenic effect on epidermal cells, both in vitro and in vivo. Anagen-phase hair bulbs plucked from men applying minoxidil showed a significant increase in proliferation index as measured by DNA flow cytometry. Minoxidil also has been shown to prolong the survival time of keratinocytes in vitro. Finally, minoxidil may oppose intracellular calcium entry. Calcium influx normally enhances epidermal growth factors to inhibit hair growth. Minoxidil is converted to minoxidil sulfate, which is a potassium channel agonist and enhances potassium ion permeability, thus opposing the entry of calcium into cells. Local vasodilatation does not appear to play a primary role in hair growth associated with minoxidil.

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