Probenecid: Probenecid decreases the renal tubular secretion of amoxicillin. Concurrent use with Cilamox may result in increased and prolonged blood levels of amoxicillin.
Allopurinol: The concurrent administration of allopurinol and ampicillin causes substantial increases in the incidence of rashes compared to administration of ampicillin alone. It is not known whether this potentiation of ampicillin rashes is due to allopurinol or the hyperuricaemia present in these patients.
Similar reactions can be expected with amoxicillin.
Oral contraceptives: In common with other broad-spectrum antibiotics, patients should be warned that Cilamox may reduce the effectiveness of oral contraceptives.
Drug/Laboratory Test Interactions: Oral administration of Cilamox results in high concentrations of amoxicillin in the urine. Since high urine concentrations of ampicillin may yield false reactions when testing for the presence of glucose in urine using *Clinitest*, Benedict's solution or Fehling's solutions it is therefore recommended that tests based on enzymatic glucose oxidase reactions such as *Clinistix* or *Tes-Tape* should be used.
A transient decrease in plasma concentration of total conjugated oestriol, oestriol-glucuronide, conjugated oestrone and oestradiol was observed following administration of ampicillin to pregnant women. This effect may also occur with amoxicillin.