Probenecid decreases the renal tubular secretion of amoxicillin. Concurrent use with co-amoxiclav may result in increased and prolonged blood levels of amoxicillin. Co-administration of probenecid cannot be recommended.
Penicillins reduce the excretion of methotrexate (potential increased toxicity).
Drug/Laboratory Test Interactions: Administration of co-amoxiclav will result in high urine concentrations of amoxicillin. High urine concentrations of ampicillin may result in false-positive reactions when testing for the presence of glucose in urine using Benedict's or Fehling's solution. Since this effect may also occur with amoxicillin and therefore co-amoxiclav, it is recommended that glucose tests based on enzymatic glucose-oxidase reactions to be used.
Following administration of ampicillin to pregnant women, a transient decrease in plasma concentration of total conjugated estriol, estriol-glucuronide, conjugated estrone and estradiol has been noted. This effect may also occur with amoxicillin as well as with co-amoxiclav.
The presence of clavulanic acid in Co-amoxiclav may cause a nonspecific binding of IgG and albumin by red cell membrane leading to a false-positive Coombs' test.