Effect of Guanfacine on Opioid-induced Hyperalgesia (OIH) and Tolerance

Inclusion Criteria * 18-65 years old * Chronic neck or back pain condition for at least 3 months * VAS score of 4-8 * Has not taken an opioid for the last 3 months * Has not taken guanfacine (or other alpha-2AR agonists) for the last 6 months Exclusion Criteria * Sensory deficits at site of QST, such as peripheral neuropathy * Allergic to or has had a severe adverse reaction to study medication (i.e. opioids, guanfacine, lactose, vitamin B2 a.k.a. riboflavin) * Cannot tolerate study drugs' maximum doses * Takes vitamin B2 \> 1.6mg/day during the study * Pregnant or breastfeeding * Pending litigation * Diagnosed with Raynaud's syndrome * Has other chronic pain conditions such as fibromyalgia or joint osteoarthritis that are predominant over back and neck pain with regard to its intensity (VAS) * Has known pre-existing cardiovascular disease (i.e. arrhythmia - prolonged QT interval \> 440ms), cerebrovascular disease, hepatic or renal impairment, CNS condition, metabolic condition, or history of syncope * Hypotension (SBP \< 90 mmHg and DBP \< 60 mmHg for female or SBP \< 100 mmHg and DBP \< 60 mmHg for male; measured while in a sitting position) or bradycardia (resting heart rate \< 60 bpm) * Subjects are on antihypertensive drugs (e.g., a beta-blocker) that result in hypotension and/or bradycardia as defined above * Tests positive for non-study opioids, illicit drugs, marijuana, or non-prescribed drugs * Major psychiatric disorders that required hospitalization in the past …