Medication surveillance on intravenous cytotoxic agents: a retrospective study.

Background: Medication surveillance is not commonly performed for cytotoxic agents. Cytotoxic agents generally have a narrow therapeutic range and therefore it might be necessary to adjust the dose. Interactions may not only cause supratherapeutic ranges, but can also lead to subtherapeutic levels. Up till now, only a few studies have demonstrated the value and importance of medication surveillance in ambulatory cancer patients.

Objective: The objective of this study is to determine the prevalence and relevance of interactions with cytotoxic agents in ambulant cancer patients receiving one or more intravenous cytotoxic administrations.

Setting: This retrospective study was undertaken in the Orbis Medical Centre in Sittard, the Netherlands.

Methods: All ambulatory cancer patients receiving one or more intravenous cytotoxic treatments during the period October 2008 to April 2010 were included. Cytotoxic agent related information was determined using the hospital information system and medication history was determined using the Electronic Prescribing System (EPS) and an open care information system. Medication was entered into the EPS and medication surveillance was performed electronically using the G-standard. All alerts were generated retrospectively.

Main Outcome Measure: The prevalence and relevance of interactions between cytotoxic agents and other drugs in ambulatory cancer patients.

Results: A total of 527 ambulatory cancer patients was enrolled. The mean age of the patients was 63.6 years and 303 were female (55 %). In 24 patients a total of 58 cytotoxic agent-related interactions was detected of whom five were clinically relevant. The most frequent cytotoxic agent-related interaction was with acenocoumarol; the most relevant interactions were with antiepileptic drugs.

Conclusion: A total of 58 potential cytotoxic agent-related interactions was found. This corresponds to 11 cytotoxic agent-related interactions per 100 ambulatory cancer patients, of which one was indicated clinically relevant and should have required an intervention. The most frequently involved drug was acenocoumarol. Most drug-related interactions with cytotoxic agents are manageable and can be monitored. Prospective studies are needed to confirm the relevance of medication surveillance on cytotoxic agents.