Study on the Effect of Granisetron on Myofascial Pain in the Orofacial Muscles

Inclusion Criteria: * age ≥ 18 years * a diagnosis of myofascial pain according to the research diagnostic criteria for TMD Axis I (RDC/TMD) * duration of TMD pain ≥ 3 months * self-assessed average myofascial-TMD pain intensity of ≥ 30 mm on a 100-mm visual analogue scale (VAS) during one week prior to examination * familiar pain upon digital palpation of the masseter and/or the temporalis muscles. * The patients remain included with one or several co-diagnoses of; a) disc displacement with or without reduction, b) osteoarthrosis in the any of the temporomandibular joints (TMJ), and c) episodic or chronic tension type headache Exclusion Criteria: * diagnosed systemic muscular or joint diseases (e.g. fibromyalgia, rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis) * whiplash associated disorder * neuropathic pain or neurological disorders (e.g. myasthenia gravis, orofacial dystonia) * history of psychiatric disorders * pain of dental origin * use of muscle relaxants or any medication that might influence the response to pain * pregnancy or lactation * known hypersensitivity to granisetron