Minoxidil for persistent chemotherapy- and endocrine-therapy hair loss

Minoxidil is a potassium-channel opener that prolongs the growth (anagen) phase of hair follicles; topical 2 percent and 5 percent formulations are licensed for androgenetic alopecia and low-dose oral minoxidil (0.25 to 5 mg) is widely used off-label. In a randomised placebo-controlled trial of 22 women receiving doxorubicin-cyclophosphamide chemotherapy (Duvic et al., 1996), topical 2 percent minoxidil did not prevent hair loss but shortened the time to maximal regrowth by about 50 days. For persistent chemotherapy-induced alopecia, most often after docetaxel or after busulfan conditioning for transplant, and for endocrine-therapy-induced alopecia, the Memorial Sloan Kettering dermatology group reported that topical minoxidil produced moderate or significant improvement in around 80 percent of treated patients with endocrine-related hair thinning (Freites-Martinez et al., JAMA Dermatology 2018), and case series of low-dose oral minoxidil describe similar regrowth. There are no large randomised trials in these settings. Side effects are scalp irritation, unwanted facial hair, and with tablets fluid retention, palpitations and low blood pressure; it should be prescribed by a clinician aware of the patient's cardiac history.