Descrição
The combination of allopurinol and amoxicillin is associated with a markedly increased incidence of skin rashes (primarily maculopapular), though the rash is usually non-severe and reversible.
Mecanismo
The mechanism is not fully established; hypersensitivity is thought to involve oxypurinol (the active metabolite of allopurinol) acting as a hapten that combines with aminopenicillin antigens to trigger T-cell-mediated hypersensitivity reactions.
Significância Clínica
Epidemiological studies show a 3- to 10-fold increase in rash incidence with the combination; most rashes resolve on drug discontinuation and are not life-threatening.
Conduta
Counsel patients about the increased rash risk; discontinue amoxicillin if a rash develops and assess whether allopurinol should also be stopped; consider alternative antibiotics in patients on allopurinol.