Assessing Warfarin-Drug Interactions among Patients at a Governmental Hospital in Riyadh Province, Saudi Arabia

SUMMARY. Warfarin is used in managing and preventing thromboembolic events, but its administration is extensively known to be associated with the risk of warfarin interactions with other drugs. This retrospective study was conducted to assess warfarin-drug interactions at a governmental hospital in in Riyadh Province. Atorvastatin (7.04%), paracetamol (5.63%), bisoprolol (4.93%), and simvastatin (4.93%) were the most commonly prescribed medications among our sample of warfarin users. Our results showed that more than 77% of the prescriptions contained at least one drug interaction with warfarin. Most of the interactions we observed were either major (41.79%) or moderate (41.79%). All the major interactions increase the risk of bleeding and the documentation of warfarin’s major interaction with five medications (amiodarone, aspirin, azithromycin, simvastatin, and levofloxacin) was excellent. The documentation of warfarin’s major interaction with three medications (amoxicillin, amoxicillin/clavulanic acid, and metronidazole) was good. Clini-cians are advised to be aware of warfarin’s potential interactions and should monitor their patients’ status closely. Moreover, pharmacists should check the drug interactions between warfarin and other medications before filling the prescriptions.