A double‐blind study of the speed of onset of analgesia following intramuscular administration of ketorolac tromethamine in comparison to intramuscular morphine and placebo

• Published in: Anaesthesia 1991-07, Vol.46 (7), p.541-544
• Main Authors: RICE, A. S. C., LLOYD, J., MILLER, C. G., BULLINGHAM, R. E., O'SULLIVAN, G. M.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Analgesics; Anti-Inflammatory Agents, Non-Steroidal - administration & dosage; Anti-Inflammatory Agents, Non-Steroidal - pharmacokinetics; Anti-Inflammatory Agents, Non-Steroidal - therapeutic use; Anti‐inflammatory agents; Biological and medical sciences; Double-Blind Method; Drug Combinations; Female; Humans; Injections, Intramuscular; Ketorolac Tromethamine; Male; measurement; Medical sciences; Middle Aged; morphine; Morphine - administration & dosage; Morphine - pharmacokinetics; Morphine - therapeutic use; Neuropharmacology; nonsteroidal; Pain; Pain Measurement; Pain, Postoperative - drug therapy; Pharmacology. Drug treatments; Time Factors; Tolmetin - administration & dosage; Tolmetin - analogs & derivatives; Tolmetin - pharmacokinetics; Tolmetin - therapeutic use; Tromethamine - administration & dosage; Tromethamine - pharmacokinetics; Tromethamine - therapeutic use
• ISSN: 0003-2409; 1365-2044
• DOI: 10.1111/j.1365-2044.1991.tb09651.x

Summary A double‐blind, randomised, parallel group, placebo‐controlled study was performed in 85 patients to compare the speed of onset of analgesia following the intramuscular administration of a single dose of 30 mg of ketorolac tromethamine, 10 mg of morphine or placebo. A new, sensitive, method was used to measure the latency of analgesia. The onset of analgesia was defined by the time taken for the pain intensity score to reach a specified percentage of the baseline value. Twenty‐five percent of patients achieving a 50% reduction in baseline pain intensity score appears to be the most appropriate parameter to assess the speed of onset of analgesia of ketorolac and morphine in the postoperative setting. Paired comparison demonstrated that ketorolac had a significantly faster onset of analgesia (p = 0.03) when compared to placebo, whilst comparison of morphine to placebo analgesic latency (p = 0.06) just failed to reach significance. There was no significant difference between the analgesic onset time of ketorolac and morphine (p = 0.73). Intramuscular ketorolac and intramuscular morphine have comparable analgesic onset times in the postoperative pain context. However, the sensitive method of measuring onset of analgesia described, highlights the slow onset of analgesia when analgesics of known efficacy are given by the intramuscular route in the postoperative period. More attention should be given to the speed of onset of analgesia in future assessments of analgesics.