Pain assessment after intramuscular injection

Several parameters (pH, osmotic pressure) influencing the local tolerance of injectable drugs have been well-documented; however, little attention has been paid to pain following an injection--a common problem in clinical practice. A pain questionnaire was used to record pain up to 24 h after a deep ventrogluteal injection. Two groups of healthy volunteers were recruited: the first group (n = 6) received 3 different cotrimoxazole preparations and placebo and the second group (n = 10) received 4 different multivitamin preparations and placebo (double-blind, cross-over). Parameters monitored during and after injection included pain localization (line drawing), pain intensity (visual-analog scale: VAS) and verbal description of pain (pain rating index: PRI). In both groups, the equality of pain (VAS, PRI) induced by the preparations was rejected in all cases (Friedman's test, p < or = 1%). The pairwise comparisons of the groups showed significant differences (p < or = 5%) between various preparations. The correlation (Spearman's rank correlation) between pain parameters VAS and PRI was high. The present investigations have shown that the pain questionnaire is a valuable tool to investigate the subjective pain symptoms during and after the injection of different preparations.