Evaluation of Potential Drug-drug Interactions in Patients with Hematologic Malignancies at a Referral Hematology–oncology Hospital: A Single-center Experience

Background: Drug-drug interaction (DDI) is a complication that results from the combined use of two or more drugs. DDIs can create problems and increase drug toxicity. In some DDIs, a drug can reduce the effectiveness of other drugs. The treatment regimen of hematologic malignancies includes various medicines. Patients may have another disease and receive other medicines in their treatment regimen, resulting in an elevation of DDI rate. This study was aimed to study the rate, pattern, and probable risk factors for moderate and major interactions. 
Subjects and Methods: In this cross-sectional study, data including type of administrated drugs, type of malignancies, and patients’ demographic data were obtained from medical records of patients referred to Tohid Hospital, Sanandaj, Iran, between 2011 and 2015. Major or moderate interactions were considered eligible for further analysis and minor interactions were excluded. DDIs were identified by Lexicomp software and Drug Interaction Facts book. Data analysis was carried out by descriptive statistics. 
Results: A total of 441 DDIs (moderate to major) were identified in 76 patients. DDIs in men were higher compared to women. In addition, most of the interactions in terms of intensity were moderate (62% of total interactions) and in terms of mechanism were pharmacodynamic (60% of total interactions). Interaction between acetaminophen and granisetron had the highest frequency. Among cancer drugs, cyclophosphamide (7% of total interactions) and among non-cancer drugs, granisetron (10% of total interactions) had the highest frequencies. 
Conclusion: Moderate or major DDIs occurred frequently in patients with blood cancer or related diseases. Most of the found DDIs were categorized as moderate with regard to severity. DDIs identification by the treatment team and replacement of treatment regimen will impose fewer complications on patients and increase patients’ survival.