Ketoconazole

Ketoconazole is an antifungal compound initially developed to treat dandruff and severe psoriasis. It has been discovered to be effective in increasing both the number and diameter of hair, which is notable considering it was not primarily intended for hair growth. The compound works by disrupting fungal growth on the scalp. Ketoconazole also appears to mildly reduce dihydrotestosterone (DHT), which helps in maintaining hair that would otherwise be lost.

It's recommended to use a ketoconazole shampoo with a concentration of at least 2% for it to be effective in hair maintenance. Users should apply the shampoo two to four times per week, keeping it on the scalp for three to five minutes to allow sufficient contact time. However, the compound can have side effects such as scalp irritation or hair becoming thin, dry, and brittle. Using biotin-enriched shampoos might help offset these side effects 1 2.