Determinants of potential drug-drug interaction associated dispensing in community pharmacies in the Netherlands.

OBJECTIVE: There are many drug-drug interactions (D-DI) of which some may cause severe adverse patient outcomes. Dispensing interacting drug combinations should be avoided when the risks are higher than the benefits. The objective of this study was to identify determinants of dispensing undesirable interacting drug combinations by community pharmacies in the Netherlands.

METHODS: A total of 256 Dutch community pharmacies were selected, based on the dispensing of 11 undesirable interacting drug combinations between January 1st, 2001 and October 31st, 2002. These pharmacies were sent a questionnaire by the Inspectorate for Health Care (IHC) concerning their process and structure characteristics.

MAIN OUTCOME MEASURE: The number of times the 11 undesirable interacting drug combinations were dispensed.

RESULTS: Two hundred and forty-six questionnaires (response rate 96.1%) were completed. Dispensing determinants were only found for the D-DI between macrolide antibiotics and digoxin but not for the other 10 D-DIs. Pharmacies using different medication surveillance systems differed in the dispensing of this interacting drug combination, and pharmacies, which were part of a health care centre dispensed this interacting drug combination more often.

CONCLUSION: Medication surveillance in Dutch community pharmacies seems to be effective. Although for most D-DIs no determinants were found, process and structure characteristics may have consequences for the dispensing of undesirable interacting drug combinations.