Study of Orofacial Pain and PropRANOlol

Purpose:

Primary: To evaluate the efficacy of extended-release (ER) propranolol compared to placebo in the reduction of a pain index in patients with temporomandibular disorder (TMD).

Secondary: To determine if extended-release propranolol efficacy varies according to participants' catechol-O-methyltransferase (COMT) genetic polymorphisms and to investigate the efficacy of extended-release propranolol compared with placebo using secondary endpoints.

Exploratory: To investigate whether the efficacy of extended-release propranolol in the reduction of the pain index varies according to participants' polymorphisms in 3 other genetic regions and according to various phenotypic characteristics.

Participants:

200 patients with chronic TMD will be randomly assigned, in a 1:1 parallel, double-blind fashion, to receive either extended-release propranolol or placebo at one of three study sites: University of North Carolina-Chapel Hill School of Dentistry; University of Florida-Gainesville College of Dentistry; and the State University of New York at Buffalo School of Dental Medicine.

Procedures (methods):

Randomization will be to either propranolol or placebo. The 10-week study treatment period is divided into: 1 week of drug titration, 8 weeks of drug maintenance, and 1 week of drug tapering. The titration and tapering doses are 60 mg (capsules) once per day orally; the maintenance dose is 60 mg twice per day orally. Participants will attend 6 clinic visits over 12-15 weeks as follows: screening and baseline visit (Visit \[V\] 0, 7-21 days prior to V1); randomization and start of treatment (titration) (V1, study day 0); maintenance visit 2 (V2, 1 week post-randomization, study day 7+3); maintenance visit 3 (V3, 5 weeks post-randomization, study day 35 +/- 7); tapering visit (V4, 9 weeks post-randomization, study day 63 +/- 7); and tapering visit 5 (V5, 11 weeks post-randomization and 1 week after drug tapering ends, study day 77 +/- 7). Depending on the visit, procedures will include: reviews of medical history, weekly alcohol consumption, concomitant therapies and medications, adverse events, compliance, and eligibility; administration/review of questionnaires; blood draw; pregnancy test in women of childbearing potential; and dispensing of study drug.

"Temporomandibular disorder" (TMD) encompasses all musculoskeletal disorders of the masticatory system and includes myalgia, arthralgia, temporomandibular joint (TMJ) disc displacements, and TMJ degenerative joint diseases. The prevalence of TMD ranges from 6% to 12% in the general population, with muscle dysfunction the most prevalent TMD diagnostic group. TMD is associated with substantial disability and suffering and negatively impacts quality of life. Jaw pain is the most common symptom that compels treatment seeking. In addition to facial pain, TMD patients frequently report comorbid pain conditions such as headache, low back pain, and fibromyalgia. New approaches to TMD therapy are urgently needed to improve clinical outcomes and reduce economic impact of this disorder.

There is currently no FDA-approved product labeled specifically to manage/treat TMD; however, classes of drugs are used to relieve TMD-associated pain, such as non-steroidal anti-inflammatory drugs (NSAIDs), anti-inflammatory drugs, corticosteroids, benzodiazepines, sedative hypnotics, muscle relaxants, opioids, antidepressants, and anticonvulsants - although evidence to establish their efficacy and safety in this population is scarce. Practitioners' justification for their use may be based on poorly controlled clinical trials or clinical trials in other pain disorders such as acute postsurgical dental pain, arthritic pain, chronic lower back pain, and neuropathic pain. Thus, there is a need for controlled clinical trials to better understand the physiological mechanisms responsible for TMD symptoms.

Evidence suggests that enhanced β-adrenergic drive contributes to the pathogenesis of TMD and other complex persistent pain conditions. For example, individuals with myofascial pain conditions have elevated catecholamine levels and augmented sympathetic responses to stressors. While increased β-adrenergic drive appears to heighten pain, β-adrenergic antagonists can reduce clinical pain and/or nociceptive sensitivity. A recent study of a single infusion of propranolol in TMD and fibromyalgia patients revealed short-term improvement in clinical pain ratings. The antagonist pindolol was similarly efficacious in alleviating cardinal symptoms of fibromyalgia pain. In addition, intramuscular injections of low-dose propranolol in rats reduced inflammatory pain associated with carrageen-induced inflammation of the gastrocnemius muscle.

The study hypothesis is that therapy with the nonselective β-adrenergic receptor antagonist propranolol extended-release capsules (FDA approved to treat many cardiac conditions, tremor, migraine, and pheochromocytoma) will provide efficacious and safe treatment for painful TMD. It has well-studied pharmacodynamic, pharmacokinetic, and side-effect profiles. Peak blood level occurs at approximately 6 hrs, and the plasma half-life is approximately 10 hrs. The primary objective is to investigate the efficacy of propranolol compared with placebo over 9 weeks to reduce pain in patients with TMD. Secondary objectives are to: investigate by treatment group whether reduction in pain varies according to polymorphisms in the COMT gene coding region; and investigate the effect of propranolol compared with placebo to affect pain sensitivity, physical and emotional function, adverse effects, and use of rescue medications. Exploratory objectives are to: investigate gene-by-treatment group interaction to determine the effect of propranolol on reduction in the pain index according to polymorphisms in the COMT, beta-2 adrenergic receptor (ADRβ2), and beta-3 adrenergic receptor (ADRβ3) genetic coding regions.

Eligibility Criteria:
Inclusion:

* Diagnostic criteria for TMD: Group II, Masticatory Muscle Disorders, Myalgia
* Facial pain for at least 3 months (and at least 10 of the last 30 days at Visit 0)
* Average pain intensity rating ≥30 (0-100 numeric rating scale) over the past week or average daily pain intensity rating ≥30 on the same scale on at least 3 days over the past week
* Agrees to terms for continuing/discontinuing certain prescription/over-the-counter pain medications throughout participation
* Agrees to not commence new prescription medication, injection therapy, occlusal splint therapy or certain other pain management techniques throughout participation
* Agrees to limit consumption of alcohol to no more than 7 drinks/week (females) and no more than 14 drinks/week (males) throughout participation
* If a female of childbearing potential, agrees to use of contraception (licensed hormonal method, intrauterine device, condoms with contraceptive foam, abstinence, or partner vasectomy) throughout participation
* Able to understand and comply with study procedures and provide written informed consent

Exclusion:

* History of congestive heart failure or certain cardiac conditions including coronary artery disease, uncontrolled hypertension, or hypotension
* Bronchial asthma, nonallergic bronchospasm, renal failure or dialysis, diabetes mellitus, hyperthyroidism, fibromyalgia, or uncontrolled seizures
* Currently taking a β-blocker or certain other medications including haloperidol, intravenous verapamil, or reserpine
* Currently taking an opioid medication
* Daily prescription medication, occlusal splint therapy, or an investigational drug or treatment for pain management within past 30 days
* Injection therapy or certain other pain management techniques within last 2 weeks
* Facial trauma or orofacial surgery within past 6 weeks
* Active orthodontic treatment
* History of major depression or other psychiatric disorder requiring hospitalization within past 6 months
* Treatment for drug or alcohol abuse within the last year
* Smokes 25 or more cigarettes/day
* Currently receiving chemotherapy or radiation therapy
* Pregnant or breastfeeding