Objective To identify potential drug interactions and side effects in an oncology outpatient clinic.

Method The study was undertaken at an oncology outpatient clinic during November 2012 in Turkey. The information regarding patient demographics, drug treatments and side effects were collected retrospectively through the patient care records and potential drug interactions were identified. Side effects due to chemotherapy were assessed by using determined criteria of the National Cancer Institute Common Toxicity Criteria version 2.

Results A total number of side effects assessed in 347 patients was 9080, of those 1526 (16.96%) were graded as ‘≥1’, which accounts for 4.4 side effects per patient. The top three categories of side effects were gastrointestinal (32.30%), neurological (23.91%) and fatigue (16.12%). Men experienced more side effects than women, and there was a correlation between the number of side effects and patient's age. There were 229 drug–drug interactions identified in 126 patients (1.8 interactions per patient). There was no correlation between the number side effects and drug interactions. An estimated prevalence (36%; in 126 out of 347 patients) of drug interactions found in this study was similar to the previous studies.

Conclusions Identification of potential drug-related problems in the clinic may improve the patient monitoring process and maintain effective drug treatment in oncology settings. There is a potential role for a clinical pharmacist to be integrated into the outpatient clinic.