The potential interaction between oral anticoagulants and acetaminophen in everyday practice.
OBJECTIVE
The drug-drug interaction between oral anticoagulants (especially warfarin) and acetaminophen has been described, but evidence is conflicting and evidence for a similar interaction between acenocoumarol or phenprocoumon and acetaminophen is limited. Therefore, a study was performed to determine the influence of acetaminophen on oral anticoagulation with acenocoumarol or phenprocoumon in everyday practice.


METHODS
Included were patients from two Dutch anticoagulant clinics who had used oral anticoagulants for at least three months and who started with acetaminophen (case group) or benzodiazepines (control group).


RESULTS
Fifty-four patients were included who had a first prescription of acetaminophen in their pharmacy record (during oral anticoagulant use) and twenty patients with a first prescription of a benzodiazepine (during oral anticoagulant use). The INR (International Normalized Ratio) difference before and after acetaminophen use was not statistically significant between the two groups and showed no dose dependency.


CONCLUSIONS
These data do not demonstrate that acetaminophen, in the dosages used in everyday practice, has a clinically relevant influence on the INR in patients using acenocoumarol or phenprocoumon.
van den Bemt
P M L A
PM
Hospital Pharmacy Midden-Brabant, TweeSteden Hospital, St. Elisabeth Hospital, Tilburg, The Netherlands. PvdBemt@zamb.tsz.nl
Geven
L M
LM
Kuitert
N A
NA
Risselada
A
A
Brouwers
J R B J
JR
D000082:Acetaminophen / Q000008:administration & dosage / Q000097:blood*; D000284:Administration, Oral; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage / Q000097:blood*; D016009:Chi-Square Distribution; D004347:Drug Interactions / Q000502:physiology; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D016014:Linear Models; D008297:Male; D008875:Middle Aged
D000925:Anticoagulants; D000082:Acetaminophen