Incompatibilities: A false positive reaction for glucose in the urine may occur with Benedict's solution, Fehling's solution or Clinitest tablets. Positive Coomb's tests have occurred. Generally, Cephalosporins are incompatible with high weight molecules; therefore, they should be administered separately. Mixtures of Cefazolin with other antibiotics are not recommended. Cefazolin contains a methylthiadiazolethione, side chain and similarly to cephalosphorins containing the related N-methylthiotetrazol side-chain, may cause a disulfiram-like reaction with alcohol, and possibly enhance the effects of warfarin. The renal excretion of cefazolin and many other cephalosphorins is delayed by probenecid.