It’s not a new drug – it’s been available in topical form for hair loss since 1988 and was approved as an antihypertensive in 1979 – but .
The number of scholarly publications examining its use for hair loss has grown dramatically in the last 2 years: There were 2 in 2019, and that jumped to 17 in 2020 and 20 in 2021, with another 16 published so far this year, according to a PubMed search. An August article in The New York Times touting it as a potential cheap magic bullet is likely to drum up even more interest, said dermatologists.
The low-dose formulation is especially exciting for women, as there have been few great oral options for them, clinicians said.
Female hair loss “is devastating,” said Lily Talakoub, MD, adding that topical minoxidil (Rogaine), topical serums, and supplements “really do not provide the considerable growth that women really want to see.” Oral minoxidil is not approved by the U.S. Food and Drug Administration for hair loss, but “it has been shown in studies to cause the hairs to grow,” and has become a “lifeline” for women, said Dr. Talakoub, a dermatologist who is in private practice in McLean, Va.
“For many years we haven’t had anything new to tell patients medically,” said Lynne J. Goldberg, MD, professor of dermatology and pathology at Boston University School of Medicine. “Now, all of the sudden there’s a cheap, widely available efficacious medicine. That’s huge for female-pattern hair loss,” said Dr. Goldberg, who is also the director of the Boston Medical Center’s Hair Clinic.
“I’ve been using oral minoxidil for about 4 years with great success,” said dermatologist Eva Simmons-O’Brien, MD, who is in private practice in Towson, Md. She has used it primarily in women, mainly because she sees more women than men for hair loss.
Dr. Simmons-O’Brien said the excitement about low-dose oral minoxidil follows an increasing recognition in the medical and scientific community that hair loss is more than just a cosmetic issue.
Mechanism not fully understood
When minoxidil was first brought to market as an antihypertensive, clinicians noted hair growth in “balding patients,” which led to the development of the topical form. Even though it has been used for hair growth for decades, its mechanism of action is not fully understood. It is known that minoxidil is a vasodilator; it may also increase DNA synthesis and enhance cell proliferation, according to a review published in 2019.
“The positive effect of minoxidil on hair growth is mainly due to its metabolite, minoxidil sulfate, and the enzyme responsible for this conversion is sulfotransferase, which is located in hair follicles and varies in production among individuals,” write the authors, all affiliated with Mahidol University in Bangkok, Thailand.
Writing in the American Academy of Dermatology’s Dermatology World Insights and Inquiries, Warren R. Heymann, MD, observed that “even after decades of use,” how minoxidil improves alopecia is still not completely understood. He noted that a 2020 review found that minoxidil’s vasodilatory effects “are propagated by upregulation of vascular endothelial growth factor (VEGF), increasing cutaneous blood flow with resultant increase in oxygen and growth factor delivery to the hair follicle.” The medication prolongs the anagen phase and shortens the telogen phase, added Dr. Heymann, head of dermatology at Rowan University, Camden, N.J.
As an antihypertensive, minoxidil is given at 5-40 mg daily. Those doses have produced serious side effects such as sodium and fluid retention, ischemic heart disease, pericardial effusion, and pulmonary hypertension, according to the Thai researchers.
Those side effects have appeared to be rare with low-dose oral minoxidil. However, in JAAD Case Reports, South African researchers reported a case in which low-dose oral minoxidil may have led to cardiac side effects. A healthy 40-year-old woman, who after 3 weeks of treatment with 5% topical minoxidil, tacrolimus ointment 0.1%, clobetasol propionate ointment, 100 mg of doxycycline twice daily, and 0.25 mg of oral minoxidil daily, was hospitalized with full-body edema. An ultrasound showed fluid collections in the pericardium, pleural space, and abdomen. She also had a pleural effusion. The patient was given 40 mg of intravenous furosemide daily for 4 days, and the edema resolved.
“Having excluded other causes of pericardial effusion and anasarca in the previously healthy, young woman, we concluded that LDOM [low-dose oral minoxidil] was responsible for her clinical presentation,” write the authors.
A review of 17 studies published on-line in 2020 in the Journal of the American Academy of Dermatology found low-dose minoxidil to be safe and effective. Androgenetic alopecia was the most commonly studied, with doses of 0.25-1.25 mg proving to be effective and safe. It was also safe and effective for female-pattern hair loss, traction alopecia, chronic telogen effluvium, lichen planopilaris, alopecia areata, and permanent chemotherapy-induced alopecia.
The most common adverse effect was hypertrichosis. Other adverse events included postural hypotension and dizziness, lower-limb edema, and mild blood pressure changes.
In another multicenter, 1,404-patient safety study published in 2021 in JAAD, the authors found that hypertrichosis was the most frequent adverse event, reported by 15% of patients. Systemic adverse events included lightheadedness (1.7% of patients), fluid retention (1.3%), tachycardia (0.9%), headache (0.4%), periorbital edema (0.3%), and insomnia (0.2%). Only 29 patients (1.2%) withdrew because of these side effects.
“It definitely helps, and it’s relatively safe,” said Adam Friedman, MD, professor and chair of dermatology at George Washington University in Washington. “But I wouldn’t want to call it a game-changer,” he said, adding that it works best when used in combination with other therapies. He often uses it with a 5-alpha reductase inhibitor – finasteride (Propecia) or dutasteride (Avodart) – “rather than as a monotherapy,” said Dr. Friedman.