Age-related differences in metoclopramide requirement for pain on injection of propofol

Pain on injection is still a major problem with propofol; metoclopramide effectively decreases this pain. The purpose of this study was to evaluate the influence of aging on metoclopramide requirement for propofol-induced pain.

In a randomised, double-blind manner, 120 patients, 60 younger (aged 20-40 years) and 60 older (aged 60-80 years) adults, received placebo (saline) or metoclopramide intravenously at two different doses (2.5mg and 5 mg) [younger group n = 20 each, older group n = 20 each], with venous occlusion for 1 minute, followed by administration of propofol 0.5 mg/kg into a dorsal hand vein. A blinded researcher asked the patient to assess the pain according to a pain score (0 = none, 1 = mild, 2 = moderate, 3 = severe) during injection of propofol.

For younger patients, the incidence of propofol-induced pain was 30% in patients receiving metoclopramide 5mg (both p < 0.05), 70% in those receiving metoclopramide 2.5mg and 80% in those receiving placebo. The median pain score was lower in patients receiving metoclopramide 5mg (0) than in those receiving placebo (1.5) [p < 0.05]. For older patients, 15 patients (75%) complained of pain in the placebo group, compared with six (30%) in the metoclopramide 5mg group (p < 0.01) and seven (35%) in the metoclopramide 2.5mg group (p < 0.05). The median pain score was lower in patients receiving metoclopramide 5mg (0) [p < 0.01] or metoclopramide 2.5mg (0) [p < 0.05] than in those receiving placebo (1).

This study showed that older patients require less metoclopramide, with venous occlusion for 1 minute, to reduce pain on injection of propofol than do younger patients.