Terbinafine

What it is

Terbinafine is an allylamine antifungal. It blocks an earlier step of fungal ergosterol production, which starves the membrane and lets a toxic intermediate build up inside the fungal cell. It is used for fungal infections of the skin and nails, where it collects in keratin and stays for a long time.

A usual adult range, not a national label — the dose and the timing differ by country and by product.

Used for

• Fungal infection

Approved uses differ by country — some of these may be off-label or unapproved where you live.

What to know while taking it

It can be taken with or without food. It inhibits a liver enzyme that handles amitriptyline and metoprolol, so their effects can grow stronger, showing up as drowsiness or a slow pulse and low blood pressure. Liver enzymes ALT and AST, and the white blood cell count, are the values that can shift on treatment, and long nail courses are reviewed rather than simply continued.

When to see a doctor

See a doctor for yellow skin or eyes, dark urine, pale stools or persistent loss of appetite, for fever, sore throat or mouth ulcers that suggest a drop in white cells, for a spreading rash, and for a lasting loss of taste.

Worth knowing

• Watch liver enzymes
• Reassess the need for long courses

Markers to watch

• ALT
• AST
• White blood cells