Encyclopedia · drug with hair side effects
Phenytoin
The old epilepsy drug phenytoin is the best-documented anticonvulsant for causing excess facial and body hair, along with acne and gum overgrowth.
What it is
A prescription anticonvulsant used since the 1930s. It is cheap and generic, although newer drugs have replaced it for long-term care in many places.
How it works
The mechanism of the hair effect is not established in the sources we opened.
What the studies show
- A systematic review of 127 studies found the most robust evidence for cosmetic side effects with phenytoin (gum overgrowth, excess hair, acne) and valproate (hair loss, excess hair). Asadi-Pooya 2021
- A review covers the effect of phenytoin on skin and skin disease (we read only the title). Scheinfeld 2004
- The review we read gave no single pooled rate for the hair effect.
How it's used in studies
Antiepileptic dosing under specialist care only.
Side effects and safety
A serious drug: it can cause birth defects, has a narrow safe dose window and many interactions. Cosmetic effects are not a reason to stop without medical advice.
Bottom line
The hair signal is well replicated for excess hair, but it is a side effect, not a use. Compare topiramate, where the hair data are far weaker. Discuss with a doctor.
Fun facts
- Two old anticonvulsants top the cosmetic side-effect charts: phenytoin for extra hair and valproate for hair loss. Asadi-Pooya 2021
Studies 2
Asadi-Pooya AA et al. Cosmetic adverse effects of antiseizure medications: a systematic review. Seizure. 2021
Result: Most robust cosmetic evidence was for phenytoin (gum overgrowth, excess hair, acne) and valproate (hair loss, excess hair).
Read the study ↗Scheinfeld N. Impact of phenytoin therapy on the skin and skin disease. Expert Opin Drug Saf. 2004
Result: Review of phenytoin effects on skin (title only read).
Read the study ↗Related
- 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.
- Valproic acid (sodium valproate)A seizure and mood-stabiliser drug that grew hair as a scalp spray in one tiny trial, but taken by mouth commonly causes hair shedding and is a major birth-defect risk.
- 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.
- Drug-induced hair changesMedicines can thin hair, regrow it curly, darken or whiten it, or lengthen lashes; this table sorts the best-known links by how strong the evidence is.