| Abstract |
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Background and objective Drug interactions are an under-recognized
and not much studied issue in oncology. However cancer
patients often take many drugs besides their chemotherapy, and even
a slight increase or decrease in cytotoxic activity due to a drug
interaction could result in excessive toxicity or reduced efficacy.
The purpose of this study was to evaluate the frequency of major and
moderate interactions that involve anticancer agents in a group of
cancer patients.
Design A 10-week observational study.
Setting Patients with solid malignancies who came to Mont-Godinne
Hospital (Yvoir, Belgium) to receive chemotherapy or who were
hospitalized in oncology during the study period were included. A
clinical pharmacist questioned these patients about their ongoing
treatments (including over-the-counter (OTC) drugs, herbs, and
vitamins) and their alcohol and tobacco consumption. Three
renowned drug interaction compendia were used to identify drug
interactions: Micromedex Healthcare Series online, Epocrates
online, and Stockley’s Drug Interactions 2008.
Main outcome measures Frequency of interactions, type of drugs
involved, consequences and management.
Results One hundred and twenty-two patients (59 women, 63 men;
mean age, 63) were included. Patients took an average of 7.5 (range,
1–22) medications including herbs and vitamins. More than 80% of
patients used at least one OTC drug and 36% used herbs or vitamins.
A total of 41 interactions of major or moderate severity involving an
anticancer agent were identified among 25% of patients. Potential
adverse consequences were far more often an increased toxicity than a
decreased efficacy of one or both interacting drugs. 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.
Conclusions Interactions involving anticancer agents are frequent.
Unfortunately little is known about the prevalence of adverse drug
events due to these interactions. Despite this, it is essential that
preventive measures are taken to avoid increased toxicity or
decreased efficacy of the drugs, at least for more frequent and more
severe interactions. Most of the time, this simply involves surveillance
of biological or clinical parameters. In this case, collaboration
with a clinical pharmacist may be useful for the prescribing
physician. |
