[Which analgesic dosage of paracetamol?]

The purpose of this study was to evaluate the dose-response of paracetamol and to assess its plasma concentration-effect relationship. According to a randomized, double-blind, and placebo controlled design healthy volunteers (n = 11) received 0.5, 1 and 2 g paracetamol (as propacetamol) intravenously (15 min). The extent of analgesic effect was measured over 8 hours by objective pain threshold (R-III) monitoring after selective transcutaneous electrical stimulation of the ipsilateral sural nerve. Maximal R-III threshold increase is at 2 hours after 0.5 g and 2.5 hours after 1 g and 2 g. The delayed peak effects, when compared to peak plasma concentrations, draw counter clockwise hysteresis. Duration of paracetamol antinociceptive effect increased concomitantly to dosage increment. Intravenous paracetamol exerts a dose-dependent central analgesia.