I NTERACTION BETWEEN PARACETAMOL AND WARFARIN IN PATIENTS : A DOUBLE - BLIND, PLACEBO - CONTROLLED, RANDOMIZED STUDY นสภ. มารุตต์ตรีอินทองรหัส นสภ. ชฎาพรพรมปัญญารหัส แหล่งฝึก : โรงพยาบาลเชียงรายประชานุเคราะห์

O BJECTIVE Main assess the effect of paracetamol on the INR in patients receiving a stable regimen of warfarin

O BJECTIVE Secondary +investigate the mechanism +evaluate a correlation between INR variation and paracetamol intake +determine a min. duration of paracetamol administration which does not cause significant INR variations +identify early variations in clotting factor activities

PATIENTS 20 outpatients, both sex, 18+ years Target INR 2-3 On stable warfarin > 1 m (2-9 mg/day) No recent or ongoing diseases The intake of concomitant Tx as well as medication known to affect INR values allowed on condition that dosages were kept constant throughout the trial

S TUDY DESIGN Single-center, double-blind,placebo- controlled, randomized and crossover study 20 pts 10: placebo 14 d 10: paracetamol 4 g* 14 d Wash-out period 14 d Paracetamol 4 g 14 d Placebo 14 d *Doliprane®, 500 mg capsule

Run-in periodVerify stability anticoagulant treatment D 0 (before 1 st medication intake) Physical examine and blood sample taken at hospital D 2, 4, 7, 9, 11 and 14 Visit at home - examine signs of hemorrhage and thrombosis -ask about possible lapses from the protocol Ex. changing any OTC or prescription drugs -counting the returned empty blister packs and the unused paracetamol and placebo capsules -evaluate alcohol consumption and dietary intake of food containing vit.K S TUDY DESIGN ( CONT.)

Intra-individual variability of INR = 0.3 (previous studies) => INR increase > 0.5 was significant and related to an interaction between paracetamol and warfarin If 2 successive INR values were >3.5, warfarin was to be discontinued then restarted at the same dose as before If INR remained outside the target range during the wash-out period, the warfarin regimen was readjusted and the pt entered the 2 nd study period after stabilization on the new dose

R ESULT Mean age: 62±19 years (range years) 19 (10 women and 9 men) completed the study 1 pt withdrew her consent for personal reason after 4 days in the 1 st period and 1 pt had a serious protocol deviation => excluded from final analysis No bleeding events The paracetamol regimen was stop in 4 pts and 1 pt in placebo administration because of increases in 2 consecutive INR values

R ESULT ( CONT.) 1 pt had a serious non-drug-related adverse event (hospitalization for a sinoatrial block) and discontinued the trial on day 4 of the 2 nd period

R ESULT ( CONT.) No significant variations in INR were observed during the placebo period Paracetamol therapy significant rise in mean INR was observe within 2 day Continued to increase until day 7 and remained significant enhanced until the end of the Tx period In each pt, the mean INR peak was significantly higher in the paracetamol period than in the placebo period

R ESULT ( CONT.) The mean absolute AUC of factor II,VII and X chandes from baseline were significantly greater during the paracetamol period than during the placebo period No significant variation in factor V levels

C ONCLUTION Mean INR rose rapidly after the start of patacetamol and significantly increase within 1 week of paracetamol intake Paracetamol intake were signigicant reduction in the vitamin K-dependent clotting factor II, VII, and X

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รูปแบบการศึกษา จำนวนของผู้ป่วยในการศึกษา ขนาดยา การตรวจติดตาม การประเมินความร่วมมือการใช้ยาตามสั่ง ความแปลผันของ INR

เกณฑ์การคัดเข้า/คัดออก จากการศึกษา ความคงที่ของ INR การรับประทานยาอื่นร่วมด้วย

ลักษณะต่างๆ ของกลุ่มศึกษา ช่วงอายุ โรคร่วมอื่นๆ ยาอื่นๆที่ได้รับ/สมุนไพร

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