Background: Cancer patients are especially vulnerable to drug interactions, which may alter the efficacy and toxicity of treatment, leading to severe clinical consequences.
Objective: Determine the incidence of such interactions in patients receiving chemotherapy, as well as to identify the drugs most frequently involved, investigate the influence of the pharmacist's interventions and verify the degree of acceptance of pharmacist's recommendations by the medical team.
Setting: The oncology department of a Spanish tertiary hospital.
Methods: During 3 months, all the drug interactions in the regular combined with treatment for cancer were analysed using two databases, and recommendations were made when clinically significant interactions (CSI) were identified.
Main outcome measure: Incidence of CSI in oncology outpatients; drugs involved in CSI.
Results: Of the 75 patients included, 31 (41%) presented CSI. Most interactions were among drugs included in the patient's usual treatment. The principal drug groups involved in CSI were cytostatic agents, antiemetics and antidepressants. The hospital pharmacist intervened on 20 occasions (35% of the patients presenting drug interactions). These interventions mainly focused on recommendations to modify or discontinue drug prescriptions, and were followed in 94% of cases.
Conclusion: The incidence of drug interactions in cancer patients is high, and they most often involve medications to treat comorbid conditions. The pharmacist, as a member of the multidisciplinary team, can contribute significantly by checking the treatment prescribed and detecting interactions, to reduce medication-related problems and to optimise drug therapy for these patients.