title: Lack of acetaminophen ceiling effect on R-III nociceptive flexion reflex.
abstract: OBJECTIVE
  The analgesic efficacy of intravenous doses of acetaminophen (paracetamol) 0.5 g, 1 g and 2 g (administered as propacetamol) was assessed in 11 healthy subjects in a randomised, double-blind, placebo-controlled crossover study. The antinociceptive effect was assessed over 8 h by measurement of the nociceptive flexion reflex threshold (R-III) in response to selective transcutaneous electrical stimulations.
  
  
  RESULTS
  After acetaminophen 0.5 g, R-III increased to a mean maximum of 23% over baseline values; after 1 g to 28%, and after 2 g to 40%. The AUC(0-8 h) of the analgesic effects and the AUC(0-8 h) of plasma concentrations closely correlated and were dose-dependent: rs = 0.37, for R-III and rs = 0.94, for the plasma concentrations. Intravenous acetaminophen exerted a dose-dependent central antinociceptive effect.
authors.affiliation: Division of Clinical Pharmacology and Pain Center, University Hospital, Geneva, Switzerland.
authors.forename: V
authors.initials: V
authors.lastname: Piguet
authors.forename: J
authors.initials: J
authors.lastname: Desmeules
authors.forename: P
authors.initials: P
authors.lastname: Dayer
mesh_terms: D000082:Acetaminophen / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000328:Adult; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D019540:Area Under Curve; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D010147:Pain Measurement / Q000187:drug effects*; D017288:Pain Threshold / Q000187:drug effects*
chemical_list: D018712:Analgesics, Non-Narcotic; D000082:Acetaminophen