Probenecid decreases the renal tubular secretion and sulbactam. Concurrent use of probenecid with Sultamicillin may result in increased and prolonged blood levels of ampicillin and sulbactam. The concurrent administration of allopurinol and ampicillin increases substantially the incidence of rashes in patients receiving both drugs as compared to patients receiving both drug as compared to patients receiving ampicillin alone.