SITE-SPECIFIC PHARMACOKINETICS AND PHARMACODYNAMICS OF INTRAMUSCULAR MEPERIDINE IN ELDERLY POSTOPERATIVE-PATIENTS

OBJECTIVE: To examine and compare the pharmacokinetics and pharmacodyn amics of meperidine when administered intramuscularly at gluteal and d eltoid sites in elderly postoperative patients, DESIGN: Prospective, r andomized investigation. SETTING: Tertiary care university teaching ho spital. PATIENTS: Fourteen patients 60 years of age or older who were undergoing general surgery. INTERVENTION: A Single dose of meperidine 0.75 mg/kg given intramuscularly at either a deltoid or gluteal site. MAIN OUTCOME MEASURES: Pharmacokinetic (based on concentration-time cu rves) and pharmacodynamic (i.e., pain scales, need for additional pain medication) comparisons were made, based on site of meperidine inject ion. RESULTS: No statistically significant differences were found in t he maximum plasma concentration, volume of distribution, or clearance of meperidine by site of injection. Substantial interpatient variabili ty in pharmacokinetic parameters was noted for both sites (range of ma ximum concentrations: 191-500 ng/mL gluteal, 166-374 ng/mL deltoid). A lthough pain scores were similar for the two groups, four of the patie nts in the group given gluteal injection required additional breakthro ugh pain management within 4 hours of meperidine injection compared wi th one patient in the group given deltoid injection. CONCLUSIONS: Ther e is no obvious relationship between meperidine pharmacokinetic and ph armacodynamic parameters, regardless of intramuscular injection site. Breakthrough pain is common when patients are given intramuscular inje ctions postoperatively, particularly when the gluteal route is used. W hen meperidine is used for analgesia in elderly postoperative patients , consideration should be given to more rapid and predictable routes ( e.g., intravenous injection) of meperidine administration.