Analgesic efficacy and safety of intravenous paracetamol (acetaminophen) administered as a 2 g starting dose following third molar surgery

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The recommended dose for intravenous (IV) paracetamol injection in adults is 1 g, however pharmacokinetic and pharmacodynamic findings suggest that a better analgesia could be obtained with a 2 g starting dose.


A single-centre, randomised, double-blind, placebo-controlled, 3-parallel group study was performed to demonstrate the analgesic efficacy and safety of IV paracetamol 2 g. Following third molar surgery, patients reporting moderate to severe pain received a single 15-min infusion of either IV paracetamol 2 g, IV paracetamol 1 g or placebo. Efficacy and safety were evaluated over 8 h. Laboratory tests were performed before and 48 h after drug administration.


Two hundred and ninety seven patients (132 = IV paracetamol 2 g; 132 = IV paracetamol 1 g; 33 = placebo) were randomised and completed the study. The summed pain relief over 6 h (TOTPAR6) was significantly superior with IV paracetamol 2 g as compared to IV paracetamol 1 g and placebo (p < 0.0001). Pain relief scores of IV paracetamol 2 g were significantly superior to IV paracetamol 1 g and to placebo from T30′ to T8h (p < 0.0001). Median duration of analgesia was significantly longer following IV paracetamol 2 g compared to IV paracetamol 1 g and placebo (p < 0.0001). Adverse events occurred with the same frequency in the 3 treatment groups. No clinically significant changes from baseline were observed for vital signs or laboratory tests.


The analgesic efficacy of a 2 g starting dose of IV paracetamol was superior over the recommended dose of 1 g in terms of magnitude and duration of analgesic effect for postoperative pain following third molar surgery, with no significant difference between groups regarding safety.

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