RESEARCH MONOGRAPH · KDC-MN-348
Tramadol
Tramadol, sold as Ultram, is an atypical opioid analgesic that combines weak direct mu-opioid receptor binding with serotonin and norepinephrine reuptake inhibition (the SNRI mechanism shared with antidepressants). The opioid effect comes mostly from a metabolite called M1, generated by the CYP2D6 liver enzyme, which means CYP2D6 ultra-rapid metabolizers (about 7 percent of Caucasians, higher in some other populations) get dramatic opioid effects from standard doses. The dual mechanism creates two distinct hazards: opioid dependence and serotonin syndrome when combined with SSRIs or other serotonergic drugs. Not stocked by Kodiac. This monograph is provided for research and educational reference.
Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.
Atypical opioid (mu-opioid + SNRI)
A weak mu-opioid agonist with serotonin-norepinephrine reuptake inhibition; an atypical analgesic with abuse and serotonin syndrome risk.
Abstract
Tramadol ((1R,2R)-rel-2-[(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexan-1-ol; CAS 27203-92-5; molecular formula C16H25NO2; molecular weight 263.38) is an atypical opioid analgesic developed at Grunenthal in the 1970s and approved by the FDA in 1995 (Ultram). The compound is a weak mu-opioid receptor agonist (Ki approximately 2 microM, low affinity); the active metabolite O-desmethyltramadol (M1, formed via CYP2D6) has approximately 200-fold higher mu-opioid affinity. Distinct from pure opioids by additional serotonin and norepinephrine reuptake inhibition (SERT Ki approximately 1 microM, NET Ki approximately 0.4 microM), contributing to the analgesic profile and to serotonin syndrome risk when combined with other serotonergic drugs. Plasma half-life is approximately 6 hours; metabolism is via CYP2D6 (M1 production) and CYP3A4. Schedule IV in the US since 2014. The combined opioid and SNRI activity produces seizures (rare at therapeutic doses, more common in overdose), serotonin syndrome (with concurrent serotonergic drugs), and abuse potential intermediate between non-opioid analgesics and full opioids. Used as the canonical atypical opioid in research.
Mechanism of action
Weak mu-opioid agonism with active metabolite M1 driving most opioid effect (CYP2D6-dependent); concurrent SERT and NET inhibition. Atypical opioid pharmacology.
Reported research dose ranges
Clinical 50 to 400 mg in the published literature.
References
- Grond S, Sablotzki A. Clinical pharmacology of tramadol. Clin Pharmacokinet 2004.
- Lassen D, et al. The pharmacogenetics of tramadol. Clin Pharmacokinet 2015.
- Beakley BD, et al. Tramadol, pharmacology, side effects, and serotonin syndrome: a review. Pain Physician 2015.
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The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.
FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.