Anti-hair loss drug linked to 'Werewolf Syndrome' in infants

The European Medicines Agency (EMA) modified the leaflets of medications containing minoxidil, a common treatment for androgenetic alopecia, a common form of hair loss to include warnings about the risk of excessive hair growth in infants due to accidental exposure. According to Exclásior, the updates now emphasize the need to avoid infants' contact with body parts where minoxidil lotions have been applied.

This decision follows reports of eleven babies developing an abnormal increase in hair, known as hypertrichosis or "werewolf syndrome," linked to the use of minoxidil by their caregivers. El Economista reported that the Navarra Pharmacovigilance Center raised alarms about this unexpected side effect after detecting cases in the Spanish region.

In one case detailed by EL PAÍS, a nursing baby progressively developed excessive hair growth on the back, legs, and thighs over two months. The investigation revealed that the father was using 5% topical minoxidil for androgenetic alopecia and had been on parental leave to care for his son. When the baby's contact with the medication was eliminated, the hypertrichosis was reversible within months.

Following this initial report, a review of similar cases in the Spanish Pharmacovigilance System database (FEDRA) identified six more incidents involving infants whose caregivers were using topical minoxidil. El Mundo noted that the search was expanded to the European pharmacovigilance database, EudraVigilance, where three additional cases were found, bringing the total to eleven.

The Navarra Pharmacovigilance Center suggested that contact between parents using minoxidil and their babies could be the cause of hypertrichosis. Público explained that this could occur either through topical transfer (skin-to-skin) or oral exposure, such as infants sucking on contaminated objects. The center emphasized that the skin of young children is more permeable, making them more susceptible to absorbing medications administered topically.

Minoxidil is widely used to stimulate hair growth in people with androgenetic alopecia, commonly known as baldness. 20 Minutos reported that the medication works by prolonging the hair growth phase and increasing blood flow to the hair follicles. While generally safe when used correctly, minoxidil can cause side effects, including hypertrichosis in areas other than the scalp.

According to El Economista, experts recommend precautions to prevent accidental exposure to infants. These include washing hands thoroughly after applying the lotion and keeping the medication in its original, tightly closed container out of the reach of children. The updated leaflets now advise users to avoid infants' contact with treated areas of the skin.

Hypertrichosis in infants can be alarming and may lead to numerous medical tests to rule out endocrine problems. This can generate significant stress for families, as the initial investigation often focuses on causes related to the patient themselves. Additionally, excessive hair growth in infants carries the risk of causing complications in the heart and kidneys.

In a prior incident in Spain in 2019, about twenty babies developed hypertrichosis due to a mistake by the company Farma-Química Sur. El Pais reported that the company distributed batches of minoxidil packaged as if they were omeprazole to several pharmacies, which were then used to prepare compounded syrups for infants. The case is still pending trial in the criminal court.

Experts underscore the importance of responsible use of minoxidil to prevent such adverse effects. Exclásior advised that the use of minoxidil should be supervised by a doctor, and users should pay attention to new warnings in the package inserts. Additionally, it's recommended to keep the medication away from children and to use safety caps to prevent accidental ingestion.

Marival Bermejo, a professor of Pharmacy at the University Miguel Hernández (Elche), explained to El Pais how the potential of minoxidil to promote hair growth was discovered by chance. "It is a potent vasodilator that has been used in oral tablets for severe arterial hypertension for half a century. Then it was seen that some patients developed hypertrichosis, so this side effect began to be exploited against alopecia topically in the form of hydroalcoholic solutions," she stated.

This article was written in collaboration with generative AI company Alchemiq