A qualitative systematic review of morphine treatment in children with postoperative pain

Background: Postoperative pain management in children is often empirical rather than evidence based. Morphine is the pharmacological treatment most widely used and although considered safe for children, adequate scientific data on morphine's pharmacokinetics, efficacy and safety are lacking. This systematic review aimed to evaluate the available literature examining different pediatric morphine regimens with respect to dosage, analgesic efficacy and incidence of side effects. Methods: Thirty-six randomized, double-blind controlled clinical trials with 49 comparisons, including multiple dosage regimens and routes of administration were included. The primary outcome measures for analgesic efficacy (pain intensity, time to first analgesic request and need for rescue analgesics) together with the incidence of morphine-related side effects were evaluated qualitatively by significant difference (P < 0.05) as reported in the original investigations. Results: Overall, significant improvements in the defined outcome measures on analgesic efficacy were only observed when morphine was compared with inactive control interventions. No relation between morphine dosage and analgesic efficacy was detected. The most common morphine-related side effects were vomiting and sedation, with significantly higher incidences observed after morphine administration in half of all comparisons. Conclusions: Although several factors may justify its use as first line therapy in many parts of the world, morphine alone is not the most suitable analgesic for postoperative pain in pediatric patients, as it does not have superior analgesic effect and a higher incidence of side effects compared with active control interventions. More standardized clinical trials with multimodal regimens as well as guidelines for evaluating pediatric medicines are desirable in the future.