Quantity and quality of potential drug interactions with coumarin anticoagulants in the Netherlands.
OBJECTIVE
Coumarin anticoagulants are prone to potentially life-threatening drug-drug interactions due to a combination of unfavorable properties. However, real life data on the actual occurrence are scarce. The aim of this study was to quantify and qualify potential drug interactions with coumarin anticoagulants in daily practice.


METHODS
A cohort study including all users of phenprocoumon or acenocoumarol during the period 1991-2003 in the PHARMO Record Linkage System. All 24 individual drugs and 11 drug groups interacting with coumarins according to central database used in the Dutch pharmacies were considered.


METHODS
Frequency and type of potential drug interactions during anticoagulant therapy with coumarins.


RESULTS
48,627 out of 76,455 mainly acenocoumarol-users (64%) were dispensed at least one potentially interacting drug (PID) during anticoagulant therapy. About 35% of these cases were dispensed a (very) strongly interacting drug, whereas 3% were dispensed a contraindicated drug. Antibacterial drugs and NSAIDs (39% and 37% of all users, respectively) were the most frequently dispensed PIDs.


CONCLUSIONS
Potential drug interactions with coumarins frequently occur in daily practice, confronting two-thirds of patients with an increased risk of bleeding. To a large part, this is attributable to commonly prescribed medication like antibacterial drugs and NSAIDs. This situation substantiates the need for proper monitoring or new anticoagulants with less drug-drug interactions.
Penning-van Beest
Fernie J A
FJ
PHARMO Institute, P.O. Box 85222, 3508 AE, Utrecht, The Netherlands. fernie.penning@pharmo.nl
Koerselman
Jeroen
J
Herings
Ron M C
RM
D000328:Adult; D000368:Aged; D000890:Anti-Infective Agents / Q000009:adverse effects; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000009:adverse effects; D000925:Anticoagulants / Q000009:adverse effects*; D015331:Cohort Studies; D003374:Coumarins / Q000009:adverse effects*; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged
D000890:Anti-Infective Agents; D000894:Anti-Inflammatory Agents, Non-Steroidal; D000925:Anticoagulants; D003374:Coumarins; C030123:coumarin