Carbamazepine: Elevated carbamazepine levels have been reported when administered concomitantly with cefixime. Drug monitoring when these drugs are given together is advised.
Chloramphenicol: In vitro and in vivo antagonism have been noted between cephalosporins and chloramphenicol against a variety of Gram-positive and Gram-negative bacteria; therefore, it is recommended that combined therapy with chloramphenicol and a cephalosporin be avoided, particularly when bactericidal activity is considered important.
Nifedipine: Concomitant administration of cefixime and nifedipine increases oral bioavailability of cefixime as a result of higher Cmax and AUC.
Probenecid: Concomitant administration of probenecid reportedly increases Cmax and AUC of cefixime and decreases renal clearance and volume of distribution of the drug.
Salicylates: Concomitant administration of 650 mg oral dose of aspirin and a 400 mg oral dose of cefixime in healthy adult men may result in a 20-25% decrease in Cmax and AUC of cefixime but did not affect protein binding, serum t1/2 or renal clearance. This effect may not be clinically important since serum concentrations of cefixime remained higher than the MIC values reported for most susceptible organisms. However, some clinicians state that this effect may be clinically important in certain infections.
Warfarin and other anticoagulants: Increased prothrombin time, with or without clinical bleeding, has been reported when cefixime is given concomitantly.
Interference with Laboratory Tests: Nitroprusside test: A false-positive reaction for ketones in the urine may occur with tests using nitroprusside but not with those using nitroferricyanide.
Coombs' test: A false-positive Coombs' test has been reported during treatment with other cephalosporin antibiotics; therefore, it should be recognized that a positive Coombs' test may be due to the drug, e.g., Coombs' testing of newborns whose mothers have received cephalosporin antibiotics before parturition or in hematologic studies or in transfusion cross-matching procedures when antiglobulin tests are performed.
Clinitest, Benedict's Solution, Fehling's Solution: A false-positive reaction for glucose in the urine using Clinitest, Benedict's solution, or Fehling's solution may result when done during therapy with cefixime. It is recommended that other tests based on enzymatic glucose oxidase reactions (e.g., Clinistix) be used.