The
incidence of skin rashes among those taking either
ampicillin or
amoxicillin is increased by
allopurinol.
There would seem to be no strong reason for avoiding concurrent use, but prescribers should recognise that the development of a rash is by no means unusual. Whether this also occurs with
penicillins other than
ampicillin or
amoxicillin is uncertain, but it does not seem to have been reported.