Potential interactions with anticancer agents: a cross-sectional study.

BACKGROUND Patients with cancer are particularly susceptible to drug interactions (DIs), but the extent of the problem has received limited attention. We aimed to evaluate the frequency of interactions with anticancer agents in a group of cancer patients. METHODS The study was performed in a Belgian teaching hospital. One hundred and twenty-two patients with solid malignancies were included. A comprehensive drug history was performed by a clinical pharmacist. Three renowned DI compendia were used to identify DIs. RESULTS Forty-one potential interactions involving an anticancer agent and considered to be clinically significant were identified among 25% of patients. The anticancer drugs mostly involved were cisplatin and methotrexate, and the most frequent co-medications involved were vitamin K antagonists, proton pump inhibitors and diuretics. In the majority of cases, the potential adverse consequence was increased toxicity of the anticancer agent and/or of the co-medication. Less than 10% of DIs were identified by the three compendia. CONCLUSIONS Preventive measures should be taken to avoid increased toxicity or decreased efficacy of the drugs. Most of the time, this simply involves surveillance of biological or clinical parameters. Collaboration with a clinical pharmacist may be useful for the prescribing physician.