Encyclopedia · pathway modulator
PDE5 inhibitors (sildenafil, tadalafil)
Sildenafil raised growth factors in human hair papilla cells and sped up growth in mice, but its only human hair trial, a tiny open study in children with alopecia areata, showed nothing beyond spontaneous regrowth.
What it is
Erectile dysfunction and pulmonary hypertension drugs, prescription-only in the US, EU and UK. Their blood-vessel and cGMP logic resembles minoxidil's, which is why they are tried in hair.
How it works
PDE5 is highly expressed in human dermal papilla cells and follicles. Sildenafil increased papilla cell growth, raised VEGF and PDGF messenger RNA and activated ERK signalling, and topical application in mice accelerated the growth phase via more blood vessels around follicles. Choi 2018
What the studies show
- Human papilla cells in culture and mice showed the effects above. Lab and mouse data only. Choi 2018
- In an open pilot of 8 children with alopecia areata using 1% topical sildenafil twice daily for 3 months, 2 had fine hair and 1 terminal regrowth, judged to be spontaneous remission. The authors do not recommend use. Sarifakioglu 2006
- No pattern hair loss trial was found.
How it's used in studies
Topical 1% twice daily in the children's pilot.
Side effects and safety
Oral PDE5 inhibitors cause headache, flushing and low blood pressure, and are dangerous with nitrate drugs. Topical scalp safety is undefined.
Bottom line
Plausible mechanism, no usable human data. Discuss with a doctor.
Fun facts
- Viagra's target enzyme is abundant in hair papilla cells. Choi 2018
Studies 2
Choi HI et al. Novel effect of sildenafil on hair growth. Biochem Biophys Res Commun. 2018
Result: PDE5 is expressed in papilla cells; sildenafil raised proliferation, VEGF, PDGF and ERK signalling and sped anagen in mice.
Read the study ↗Sarifakioglu E et al. Determination of the sildenafil effect on alopecia areata in childhood: an open-pilot comparison study. J Dermatolog Treat. 2006
Tested: topical 1% sildenafil twice daily
Result: 2 had fine hair and 1 terminal regrowth, judged spontaneous remission; authors do not recommend use.
Read the study ↗Related
- DipyridamoleAn old antiplatelet pill that on paper boosts the same adenosine pathway topical adenosine uses, but no study has ever tested it on hair and its label lists hair loss as a rare report.
- MinoxidilThe most widely used hair-growth treatment, available as a cheap over-the-counter lotion or foam and as a prescription tablet, with a mechanism that is still only partly understood.
- MidodrineA blood-pressure pill that gives many people goosebumps and a tingling scalp because it grips the tiny muscle at each hair; related drugs briefly cut shedding during brushing, but midodrine itself has never been tested on hair.
- TopiramateAn epilepsy and migraine pill sometimes floated as a topical hair grower, although nobody has ever tested it on scalp hair; the real hair signals are reversible shedding, one case of overlong eyelashes and a small open trial in compulsive hair-pulling.