Terbinafine (Lamisil) is given orally to treat fungal skin and nail infections. Well documented side effects include stomach problems nausea, loss of appetite, abdominal pain, diarrhea skin eruptions, and kidney dysfunction, including jaundice and h

It can also cause joint and muscle pain and, as it is excreted in breast milk, should never be taken by breastfeeding mothers.

Doctors in Canada now report a previously unrecorded side effect linked to the drug, which led to two previously healthy individuals being hospitalized (Medical Monitor, 17 September 1997). Three patients with stable psoriasis where the skin erupts in red, scaly lesions found their skin condition became much worse. In one case, a patient whose rash was previously confined to her hands, feet and nails found psoriasis spread to her trunk and arms. In another, within three weeks of taking the drug for a nail infection, a woman was covered in pustular psoriasis, which needed hospital treatment.

In a fourth case, after taking terbinafine, a patient with no personal or family history of the condition also ended up in hospital with pustular psoriasis.

Doctors should be more careful about dishing out this drug, concludes the Medical Monitor. Malformed nails "can be due to fungal infections or psoriasis or even both, which cannot be clinically distinguished". A diagnosis should be confirmed before antifungal treatment is started. "There is no point in risking side-effects when the dystrophy is due to psoriasis rather than infection," it concludes.