Effect of propranolol on TMD patients: preliminary findings

Temporomandibular disorders (TMD), a heterogeneous family of musculoskeletal disorders, represent the most common chronic orofacial pain condition. Considerable evidence now suggests that the painful myalgia seen in TMD patients may result from impairment in central pain processing and enhanced beta-adrenergic drive. The aim of the research is to test whether low dose propranolol, a non-selective beta-adrenergic receptor blocker, can reduce pain and restore function in TMD patients. 40 healthy control female subjects and 40 female TMD patients will be enrolled in randomized, double-blind, crossover, placebo-controlled study of 4 weeks duration. Only TMD patients have been randomized to 40 mg of daily propranolol treatment or placebo during their first week of treatment, followed by wash-out week, and second week of propranolol or placebo treatment. Subjects have been examined using the Research Diagnostic Criteria (RDC) for TMD to assess facial function, phenotyped by Quantitative Sensory Testing (QST) with respect to their pain sensitivity to pressure and heat pain, completed daily symptom calendar and a series of psychological and pain-related questionnaires. TMD patients' thermal and mechanical pain thresholds were significantly lower than those for healthy controls and they showed enhanced temporal summation of thermal pain compared with normal subjects. Propranolol treatment data are currently available for 12 TMD patients and suggest that propranolol may increase pressure pain threshold in those patients and reduce their average daily pain ratings. When asked to indicate the treatment arm that best relieved their condition, 8 of 12 subjects identified the propranolol treatment arm. Supporting earlier studies, results from the present research show that TMD patients are hypersensitive to noxious stimuli. The preliminary finding suggests that propranolol may diminish mechanical sensitivity and pain associated with TMD.