DRUG INTERACTIONS 7.1 Effect of Other Drugs on Cyclophosphamide Exposure Protease Inhibitors Concomitant use of protease inhibitors may increase the concentration of cytotoxic metabolites and may enhance the toxicities of cyclophosphamide, including higher incidence of infections, neutropenia, and mucositis. 7.2 Drugs That Potentiate Cyclophosphamide Toxicities Radiation therapy or drugs with similar toxicities to Cyclophosphamide for Injection can potentiate toxicities for cyclophosphamide. Monitor for increased toxicities in patients receiving radiation therapy or drugs known to cause: • Myelosuppression and/or immunosuppression [ see Warnings and Precautions ( 5.1 ) ] • Nephrotoxicity including hemorrhagic cystitis [ see Warnings and Precautions ( 5.2 ) ] • Cardiotoxicity [ see Warnings and Precautions ( 5.3 ) ] • Pulmonary toxicity [ see Warnings and Precautions ( 5.4 ) ] • Secondary malignancies [ see Warnings and Precautions ( 5.5 ) ] • Hepatotoxicity including liver necrosis and VOD [ see Warnings and Precautions ( 5.6 ) ] 7.3 Effect of Cyclophosphamide on Other Drugs Metronidazole Acute encephalopathy has been reported in a patient receiving cyclophosphamide and metronidazole.
Source: FDA drug label - cyclophosphamide for injection