<p>Additive myelosuppression with other myelosuppressive agents. Cytotoxic agents may increase risk of pulmonary toxicity. May reduce response to vaccines, possibility of generalised infections with live vaccines. Increased risk of adverse effects if given in conjunction with or soon after radiotherapy. Decreased clearance when used wit cyclophosphamide, itraconazole or paracetamol. Combination with thioguanine may result in oesophageal varices, hepatotoxicity and portal HTN. Increased clearance by phenytoin.</p>