Minoxidil: mechanisms of action on hair growth

Abstract

We have known for over 30 years that minoxidil stimulates hair growth, yet our understanding of its mechanism of action on the hair follicle is very limited. In animal studies, topical minoxidil shortens telogen, causing premature entry of resting hair follicles into anagen, and it probably has a similar action in humans. Minoxidil may also cause prolongation of anagen and increases hair follicle size. Orally administered minoxidil lowers blood pressure by relaxing vascular smooth muscle through the action of its sulphated metabolite, minoxidil sulphate, as an opener of sarcolemmal KATP channels. There is some evidence that the stimulatory effect of minoxidil on hair growth is also due to the opening of potassium channels by minoxidil sulphate, but this idea has been difficult to prove and to date there has been no clear demonstration that KATP channels are expressed in the hair follicle. A number of in vitro effects of minoxidil have been described in monocultures of various skin and hair follicle cell types including stimulation of cell proliferation, inhibition of collagen synthesis, and stimulation of vascular endothelial growth factor and prostaglandin synthesis. Some or all of these effects may be relevant to hair growth, but the application of results obtained in cell culture studies to the complex biology of the hair follicle is uncertain. In this article we review the current state of knowledge on the mode of action of minoxidil on hair growth and indicate lines of future research.

Plucked human hair as a tissue in which to assess pharmacodynamic end points during drug development studies

“…However, the relative positive nuclear count frequencies for the different markers in other healthy human tissues are fully consistent with the majority of these zero counts being 'biological'. Whether low levels of markers could be reliably increased prestudy in order to make them more practicable, for example, through the use hair stimulants such as minoxidil (Messenger and Rundegren, 2004), is currently unknown. The final evaluation of the usefulness of any of these markers as study end points will depend on demonstrating PD activity on them within a future drug-intervention study.…”

Visible-to-Near IR Quantum Dot–Based Hypermulticolor High-Content Screening of Herbal Medicines for the Efficacy Monitoring of Hair Growth Promotion and Hair Loss Inhibition

“…Finasteride and minoxidil are two well-known drugs for hair loss. 6,7 Finasteride is a synthetic 5-α-reductase inhibitor, and minoxidil is a vasodilator, both of which suppress male hormones and are used to treat alopecia. However, the use of two drugs should be limited due to strong side effects.…”

Structural Requirements of Minoxidil Analogs for Enhancing Lysyl Hydroxylase Inhibitory Activity

“…현재까지 Minoxidil은 상피세포와 섬유아세포의 생장을 자극하거나 lysyl hydroxylase (LH)저해, 콜라겐 생성저해, prostaglandin E 2 (PGE 2 ) 합성을 자극하여 prostacyclin의 생 산저해 및 피부돌기 세포에 의한 VEGF (vascular endothelial growth factor)의 합성을 자극하는 것으로 알려졌다 [5]. 이 와 같이 세포기능에 다양한 영향을 미치고 있으나 어떤 표적 을 통하여 발모에 영향을 미치는지에 대한 연구는 부족한 실정이다.…”