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Interaction between acetaminophen and warfarin in adults receiving long-term oral anticoagulants: a randomized controlled trial นศภ. ณัฐวุฒิ ดวงแดง มหาวิทยาลัยเชียงใหม่ นสภ. จตุพร ใจเคลื่อนมหาวิทยาลัย พะเยา นสภ. อังสนา เพ็ญสมบูรณ์ มหาวิทยาลัยพะเยา
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Click to add Title 1 2 3 4 Title
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impact factor = 2.743
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Abstract
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Introduct ion The mean INR increase in patients receiving acetaminophen at the highest recommended dosage (4 g/day) No prospective study has yet evaluated the effect of acetaminophen at 3 g/day
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Acetaminophen given at 2 g/day and 3 g/day might potentiate the anticoagulant effect of warfarin Research questions
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Objec tive To evaluate the effect of acetaminophen, given at 2 g/day and 3 g/day, on INR in stable patients treated with warfarin
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Study Design randomized, parallel (three arms), double- blind, placebo-controlled study
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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 Laboratory values remained within normal limits
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Exclusion criteria Any treatment change within 7 days before enrollment Any paracetamol intake within the last 14 days St John's wort treatment
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Exclusion criteria Drug allergy Concomitant drug ( 5- fluorouracile, acetylsalicylic acid, non steroidal anti- inflammatory drugs, chloramphenicol, diflunisal, miconazole) Pregnancy
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Drop out INR value were higher than 3.5 Drug known to interact with warfarin or acetaminophen
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Method 45 Patients Control group (9)Experimental group (36) 2 g/day (18) 3 g/day (18) Placebo (9) Acetaminophen
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Method Placebo two placebo tablets three times a day two placebo tablets three times a day 2 g/day two 500 mg tablets twice a day + two placebo tablets once daily two 500 mg tablets twice a day + two placebo tablets once daily 3 g/day two 500 mg tablets three times a day two 500 mg tablets three times a day
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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 concentrations between groups
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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-type Osteocalcin and undercarboxylated Osteocalcin plasma concentrations between groups
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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
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Statistics ความเหมาะสมของสถิติที่ใช้กับชนิดของตัวแปร - 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
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Result
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Fig. 1 Correlation between INR changes and acetaminophen plasma concentrations
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Result Fig. 2 Correlation between INR changes and factors II plasma concentrations
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Result Fig. 3 Correlation between INR changes and factors VII plasma concentrations
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The lack of variables follow up after withdrawal of acetaminophen The unexpected imbalance observed in the randomization of the population regarding age, gender and basal warfarin dose Limitation of Research
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Conclusion - Acetaminophen, 2 g/day and 3 g/day significantly increased the INR in patients treated with warfarin - Recommend close INR monitoring in patients taking acetaminophen during warfarin therapy
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Generaliza bility - European pt. -> Genetics variation - Life style and environment - Other drugs and agents - Disease
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Thank you
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