Objectives: To evaluate the nature, type and prevalence of potential drug-drug interactions (DDIs) in prescriptions dispensed in community pharmacies in Thessaloniki, Greece. Secondary objectives included the classification of DDIs as per pharmacotherapeutic class of the medications and the investigation of the relationship between medical specialties and the frequency of potential DDIs, as well as the relationship between DDIs and prescription size. Setting DDIs are a common cause of adverse drug reactions (ADRs) among patients using multiple drug therapy. In Greece a reliable computerized surveillance system for monitoring potential DDIs is not yet fully established. As a result, the prevalence of such DDIs in prescriptions dispensed by community pharmacies in Greece is unknown.
Methods: We conducted a prospective, descriptive study. Over a 3-month period (November 2007-January 2008), a total of 1,553 handwritten prescriptions were collected from three community pharmacies in Thessaloniki, Greece. The prescriptions were processed using the Drug Interactions Checker within the www.drugs.com database. The identified potential DDIs were categorized into two classes, major and moderate, according to their level of clinical significance.
Main outcome measures: Overall 213 prescriptions had one or more potential DDIs and a total of 287 major and moderate DDIs were identified. Potential DDIs were identified in 18.5% of all prescriptions. Major DDIs were identified in 1.9% of all prescriptions and represented 10.5% of all DDIs detected, whereas moderate DDIs were identified in 16.6% of all prescriptions and represented 89.5% of all DDIs detected. The rate of DDIs increased with prescription size. The most common drug involved in major DDIs was amiodarone which interacts with potassium-wasting diuretics, digoxin, simvastatin and acenocoumarol.
Conclusions: Our results indicate that patients in Greece are at risk of ADRs caused by medications due to potential DDIs. An appropriate surveillance system for monitoring such interactions should be implemented and physicians should be more aware of potentially harmful DDIs. Pharmacists can contribute to the detection and prevention of drug-related injuries, especially of clinically meaningful DDIs that pose a potential risk to patient safety.