Pharmacologic Management of Myofascial Pain

Abstract Myofascial pain is thought to occur by peripheral and central mechanisms. Peripheral factors include trauma, dysregulated deep-tissue microcirculation, and altered muscular metabolism and mitochondrial function. Supraspinal mechanisms include decreased modulatory activity, hippocampal suppression, and possibly impaired stress responses. Myogenic pain has been reported to contribute to up to 50% of temporomandibular joint disorders. Myofascial pain is characterized by the presence of loci of hypersensitivity within tender, taut, palpable bands of muscle called trigger points (TP). There is increased paraspinal muscle tone in patients suffering from chronic LBP, and muscle spasm may be superimposed on primary injuries such as acute disc herniation. Individuals with nonspecific neck pain often manifest neck muscle contractions, altered patterns of muscle activation, and elevated levels of myoelectric activity. True muscle cramps are painful involuntary skeletal muscle contractions associated with electrical activity. True muscle cramps, by definition, occur in the absence of fluid or electrolyte imbalance and have diverse etiologies. Seventy percent of patients with tension headaches suffer from muscle tightness and tenderness, with the percentage even higher in individuals suffering episodic headaches. Studies showed TCAs to be effective in reducing the frequency and intensity of TTHs and facial pain/TMD. Gabapentin and pregabalin are first-line agents for the treatment of neuropathic pain but have also demonstrated some effectiveness in conditions characterized by muscle pathology. Studies showed varying effectiveness of muscle relaxants compared to other medications. Studies have shown conflicting results regarding the use of benzodiazepines in TMD and TTH. The evidence for their effectiveness in muscle spasm is moderate, and their adverse effect profile and inferiority compared to traditional muscle relaxants preclude their routine use. NSAIDs are considered to be a first-line treatment for acute TTH, though persistent use may lead to rebound headaches. In TMD, NSAIDs can be beneficial although the evidence is limited by the poor quality of the studies. Controlled studies showed botulinum toxin to be effective in myofascial pain. Opioids may provide short-term benefit for certain conditions characterized by myofascial pain, but they have not been shown to definitively provide long-term benefit, improvement in function, or greater benefit when compared to nonopioid therapy. The efficacy of topical treatments in myofascial pain has not been consistently shown.