A 45-year-old female presents with a rash. She has
recently been treated by her GP for an urinary tract infection.
On examination she has a symmetrical rash mainly
affecting the limbs, especially her hands and feet. The lesions consist of
three concentric rings of colour change; a central blister surrounded by a
pale oedematous zone, which in turn is surrounded by an area of erythema.
The most likely drug that has been prescribed by the GP