Co-administration of morphine and gabapentin leads to dose dependent synergistic effects in a rat model of postoperative pain

Morphine combined with gabapentin produces dose dependent synergistic antihyperalgesic effects in a rat model of postoperative pain. Using different dose combinations in the rat plantar incision model, researchers measured pain related responses with an electronic von Frey device. They quantified effects with % maximum possible effect (%MPE) and area under the response curve (AUC), then identified synergy with Loewe additivity response surface analyses. The combination generated synergy that was dose dependent, with the observed response exceeding theoretical additive expectations by about 26 to 58% for synergistic doses. The results suggest gabapentin could be an adjuvant to morphine to potentially reduce required morphine dose, though translation to humans would need further study.