Interacties en dubbelmedicatie bij poliklinische patiënten met kanker

Objective: The pharmacotherapeutic treatment of patients with cancer is generally associated with multiple side-effects. Drug interactions can reinforce or intensify side-effects. We assessed the prevalence of drug interactions among ambulatory cancer patients being treated with cytotoxic drugs using a novel advanced screening method. Design and methods: The patients were asked to complete a questionnaire and an interview to obtain demographic and medication data. Drug interactions were identified by using electronic (Drug Interaction Facts software, version 4.0) and manual (e.g. PubMed) screening methods. Results: In this study 278 patients were enrolled and 348 potential drug interactions were identified. Of all patients 161 (58%; 95% confidence interval 52-64%) experienced at least one interaction. Of all drug interactions 34% was classified as major and 60% as moderate. In 40% of all drug interactions an anti-cancer agent and in 60% a supportive agent was involved. OTC drugs were involved in 11% of all drug interactions. Drug interactions with Cumarins, quinolones, anti-epileptics and hydrochlorothiazide were seen frequently. Interactions that potentially cause QT prolongation, gastroduodenal toxicity and CNS depression were also common. Duplicate prescriptions were not found. Conclusion: Potential drug interactions are common in (hemato)oncology. Screening for drug interactions should take place routinely before administering cytotoxic drugs.