RESUMEN
Methadone is a mu (µ) opioid receptor agonist used clinically in adults and children to manage opioid use disorder, neonatal abstinence syndrome, and acute and chronic pain. It is typically marketed as a racemic mixture of R- and S-enantiomers. R-methadone has 30-to 50-fold higher analgesic potency than S-methadone, and S-methadone has a greater adverse effect (prolongation) on the cardiac QTc interval. Methadone undergoes stereoselective metabolism. CYP2B6 is the primary enzyme responsible for catalyzing the metabolism of both enantiomers to the inactive metabolites, S- and R-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (S- and R-EDDP). Genetic variation in the CYP2B6 gene has been investigated in the context of implications for methadone pharmacokinetics, dose, and clinical outcomes. Most CYP2B6 variants result in diminished or loss of CYP2B6 enzyme activity, which can lead to higher plasma methadone concentrations (affecting S- more than R-methadone). However, the data do not consistently indicate that CYP2B6-based metabolic variability has a clinically significant effect on methadone dose, efficacy, or QTc prolongation. Expert analysis of the published literature does not support a change from standard methadone prescribing based on CYP2B6 genotype (updates at www.cpicpgx.org).
RESUMEN
CLINICAL QUESTION: What is the comparative effectiveness of available therapies for chronic pain associated with temporomandibular disorders (TMD)? CURRENT PRACTICE: TMD are the second most common musculoskeletal chronic pain disorder after low back pain, affecting 6-9% of adults globally. TMD are associated with pain affecting the jaw and associated structures and may present with headaches, earache, clicking, popping, or crackling sounds in the temporomandibular joint, and impaired mandibular function. Current clinical practice guidelines are largely consensus-based and provide inconsistent recommendations. RECOMMENDATIONS: For patients living with chronic pain (≥3 months) associated with TMD, and compared with placebo or sham procedures, the guideline panel issued: (1) strong recommendations in favour of cognitive behavioural therapy (CBT) with or without biofeedback or relaxation therapy, therapist-assisted mobilisation, manual trigger point therapy, supervised postural exercise, supervised jaw exercise and stretching with or without manual trigger point therapy, and usual care (such as home exercises, stretching, reassurance, and education); (2) conditional recommendations in favour of manipulation, supervised jaw exercise with mobilisation, CBT with non-steroidal anti-inflammatory drugs (NSAIDS), manipulation with postural exercise, and acupuncture; (3) conditional recommendations against reversible occlusal splints (alone or in combination with other interventions), arthrocentesis (alone or in combination with other interventions), cartilage supplement with or without hyaluronic acid injection, low level laser therapy (alone or in combination with other interventions), transcutaneous electrical nerve stimulation, gabapentin, botulinum toxin injection, hyaluronic acid injection, relaxation therapy, trigger point injection, acetaminophen (with or without muscle relaxants or NSAIDS), topical capsaicin, biofeedback, corticosteroid injection (with or without NSAIDS), benzodiazepines, and ß blockers; and (4) strong recommendations against irreversible oral splints, discectomy, and NSAIDS with opioids. HOW THIS GUIDELINE WAS CREATED: An international guideline development panel including patients, clinicians with content expertise, and methodologists produced these recommendations in adherence with standards for trustworthy guidelines using the GRADE approach. The MAGIC Evidence Ecosystem Foundation (MAGIC) provided methodological support. The panel approached the formulation of recommendations from the perspective of patients, rather than a population or health system perspective. THE EVIDENCE: Recommendations are informed by a linked systematic review and network meta-analysis summarising the current body of evidence for benefits and harms of conservative, pharmacologic, and invasive interventions for chronic pain secondary to TMD. UNDERSTANDING THE RECOMMENDATION: These recommendations apply to patients living with chronic pain (≥3 months duration) associated with TMD as a group of conditions, and do not apply to the management of acute TMD pain. When considering management options, clinicians and patients should first consider strongly recommended interventions, then those conditionally recommended in favour, then conditionally against. In doing so, shared decision making is essential to ensure patients make choices that reflect their values and preference, availability of interventions, and what they may have already tried. Further research is warranted and may alter recommendations in the future.