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Clin Pharmacol Ther. 1994 Apr;55(4):464-70.

A placebo-controlled model to assay the onset of action of nonprescription-strength analgesic drugs.

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  • 1Department of Epidemiology and Biostatistics, McGill University, Montréal, Québec, Canada.


The definition and detection of the onset of analgesic drug activity represent two of the more complicated methodologic challenges in clinical pharmacology. We addressed these issues by designing an analgesic assay with frequent posttreatment assessments to identify the first time when a subject experienced relief and when a nonprescription-strength analgesic could be distinguished from placebo. To test the feasibility of conducting this assay, 29 subjects with acute sore throat were randomized to receive 200 mg ibuprofen, 400 mg ibuprofen, or placebo under double-blind conditions. To identify the onset of analgesia, subjects used three rating scales at 5-minute intervals over the first hour. Subjects completed each series of assessments efficiently, most within 5 seconds. Each active agent was differentiated from placebo early after treatment (p < or = 0.05), and there was dose-separation. We conclude that the sore throat pain model can be used to evaluate the onset of action of nonprescription-strength analgesic agents.

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