Transcript Journal Club

Interaction between
acetaminophen and warfarin in
adults receiving long-term oral
anticoagulants: a randomized
controlled trial
นศภ.ณัฐวุฒ ิ
ดวงแดง
มหาวิทยาลัยเชียงใหม่
นสภ.จตุพร ใจเคลือ
่ น
มหาวิทยาลัย
พะเยา
นสภ.อังสนา
เพ็ญสมบูรณ ์
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impact factor =
2.743
Abstract
Introductio
n
 The mean INR increase in
patients receiving
acetaminophen at the highest
recommended dosage (4
g/day)
 No prospective study has yet
Research
 Acetaminophen
questionsgiven at 2
g/day and
3 g/day might potentiate the
anticoagulant
effect of warfarin
Objecti
ve
 To evaluate the effect of
acetaminophen, given at 2
g/day and 3 g/day, on INR in
stable patients treated with
warfarin
Study Design
 randomized, parallel (three
arms), double-blind,
placebo-controlled study
Inclusion
criteria
 Patients treated with
warfarin (target INR 2 to 3)
stable anticoagulation at
2 to 9 mg for more than 30
days
 Aged 18 years or older
Exclusion
criteria
 Any treatment change
within 7 days before
enrollment
 Any paracetamol intake
within the last 14 days
 St John's wort treatment
Exclusion
criteria
 Drug allergy Concomitant
drug
( 5fluorouracile, acetylsalicylic
acid, non steroidal antiinflammatory drugs,
chloramphenicol, diflunisal,
miconazole)
Drop out
 INR value were higher than
3.5
 Drug known to interact with
warfarin or acetaminophen
Method
45 Patients
Control group Experimental
(9)
group (36)
Placebo (9)
Acetaminophen
2 g/day (18) 3 g/day
(18)
Method
Placebo
2 g/day
3 g/day
two placebo tablets
three times a day
two 500 mg tablets twice a da
+ two placebo tablets once da
two 500 mg tablets
three times a day
Outcome
 Primary outcome
- The mean maximum increase in
INR from
baseline to Day 10
 secondary outcome
- The mean maximum INR
- Day 10 - Day 1 differences in
factors II, V, VII, AT-III plasma
Outcome
 secondary outcome
- Day 10 - Day 1 differences in
acetaminophen plasma
concentration between groups
- Day 10 - Day 1 differences in R(-),
S(-)warfarin plasma concentrations
between groups
- Day 10 - Day 1 differences in Gla-
Statistics
Sample size and percent drop out
There are 45 pt. in these study.
- intra-individual INR variability is 0.3
- expected INR increase of at least 0.5
- bilateral α level of 5% และ β level of 10%
-No drop out
Statistics
ามเหมาะสมของสถิตท
ิ ใี่ ช้กับชนิดของตัวแปร
- ANOVA
-post-hoc test
-All statistical analyses were implemented by using
Statview v8.0 (SAS Institute, Cary, NC, USA)
- Results were expressed as mean and 95%
confidence interval (CI), or as a percentage, as
appropriate. A P value of 0.05 or less indicated
statistical significance
Result
Result
Fig. 1 Correlation between INR
changes and
Result
Fig. 2 Correlation between INR
changes and factors II plasma
Result
Fig. 3 Correlation between INR
changes and factors VII plasma
Limitation of
Research
 The lack of variables follow
up after withdrawal of
acetaminophen
 The unexpected imbalance
observed in the
randomization of the
population regarding age,
Conclusion
- Acetaminophen, 2 g/day and 3
g/day
significantly increased the INR
in patients
treated with warfarin
- Recommend close INR
monitoring in patients
Generalizabi
lity
- European pt. -> Genetics variation
- Life style and environment
- Other drugs and agents
- Disease
Thank
you