The inclusion of sulbactam extends ampicillin's spectrum of action to beta-lactamase producing strains of bacteria.

In Japanese clinical trials, these occurred with a frequency of 3.7% and 1.1%, respectively; however, in studies outside Japan, diarrhoea was much more common at 10% to over 50% in patients taking sultamicillin.

Other adverse effects occurring in the range of 1 to 10% of people include nausea, vomiting, stomach ache, headache, rashes, and infections with Candida albicans.

[1][5] Interactions with other drugs are similar to other penicillins: allopurinol increases the risk for patients to develop rashes.

Conversely, the elimination of sultamicillin's active constituents (ampicillin and sulbactam) is reduced by probenecid and probably by the nonsteroidal anti-inflammatory drugs (NSAIDs) aspirin, indometacin and phenylbutazone.