Antihyperalgesic efficacy of lacosamide in a rat model for muscle pain induced by TNF.

Chronic muscle pain is a problem with high prevalence in clinical practice and its pharmacological treatment is difficult. There is a lack of animal models which reliably predict analgesic activity of drugs on muscle pain. Here we used intramuscular injection of tumor necrosis factor-alpha (TNF) in rats as a model of muscle pain. In this model we tested the antihyperalgesic action of lacosamide in comparison to the analgesics pregabalin and gabapentin. Mechanical withdrawal thresholds to muscle pressure were measured with an algesimeter exerting pressure on the gastrocnemius muscles previously injected with TNF. Fore limb grip strength was measured with a digital grip force meter after TNF injection into the biceps brachii muscles. A complete reversal of hyperalgesia was seen with lacosamide at 30mg/kg. Significant effects were also seen for pregabalin at 30 and 100mg/kg and gabapentin at 100mg/kg. In biceps muscle hyperalgesia, a significant reversal of hyperalgesia was seen with lacosamide at 10mg/kg. Significant effects were also seen for pregabalin and gabapentin at 100mg/kg. We could thus demonstrate in a rat model for myalgia that lacosamide effectively reduces muscular hyperalgesia and is somewhat more potent than gabapentin and pregabalin.