|Systematic (IUPAC) name|
|Legal status||Unscheduled (US)|
|Half-life||~ 9 h|
|Mol. mass||249.349 g/mol|
| (what is this?)
(+)-O-Desmethyltramadol is the most important metabolite of tramadol produced in the liver after tramadol is consumed. This metabolite is considerably more potent as a μ opioid agonist than the parent compound.
Tramadol is demethylated by the liver enzyme CYP2D6 in the same way as codeine, and so similarly to the variation in effects seen with codeine, individuals who have a less active form of CYP2D6 ("poor metabolisers") will tend to get reduced analgesic effects from tramadol.
The two enantiomers of O-desmethyltramadol show quite distinct pharmacological profiles; both (+) and (-)-O-desmethyltramadol are inactive as serotonin reuptake inhibitors, but (-)-O-desmethyltramadol retains activity as a noradrenaline reuptake inhibitor and so the mix of both the parent compound and metabolites produced contributes significantly to the complex pharmacological profile of tramadol.
Recreational use 
O-Desmethyltramadol has recently been marketed as a currently legal substitute for illegal opioid drugs, either in powder form or mixed into various other preparations. One such blend sold under the brand Krypton and containing powdered kratom leaf (Mitragyna speciosa) laced with O-desmethyltramadol was reportedly linked to at least 9 accidental deaths from overdose during 2010-2011.
Role in drug development 
The opioid medication tapentadol was developed to mimic the actions of O-desmethyltramadol in order to create a weak-moderate analgesic which is not dependent on metabolic activation.
O-Desmethyltramadol is metabolized in the liver into the active metabolite N,O-didesmethyltramadol via CYP2D6. The inactive tramadol metabolite N-desmethyltramadol is also metabolized into the active metabolite N,O-didesmethyltramadol by the same enzyme.
See also 
- Tramadol Pharmacokinetics, PharmGKB
- Sevcik, J; Nieber, K; Driessen, B; Illes, P (1993). "Effects of the central analgesic tramadol and its main metabolite, O-desmethyltramadol, on rat locus coeruleus neurones". British Journal of Pharmacology 110 (1): 169–76. PMC 2175982. PMID 8220877.
- Dayer, P; Desmeules, J; Collart, L (1997). "Pharmacology of tramadol". Drugs. 53 Suppl 2: 18–24. doi:10.2165/00003495-199700532-00006. PMID 9190321.
- Borlak, J; Hermann, R; Erb, K; Thum, T (2003). "A rapid and simple CYP2D6 genotyping assay--case study with the analgetic tramadol". Metabolism: clinical and experimental 52 (11): 1439–43. doi:10.1016/S0026-0495(03)00256-7. PMID 14624403.
- Garrido, MJ; Valle, M; Campanero, MA; Calvo, R; Trocóniz, IF (2000). "Modeling of the in vivo antinociceptive interaction between an opioid agonist, (+)-O-desmethyltramadol, and a monoamine reuptake inhibitor, (-)-O-desmethyltramadol, in rats". The Journal of Pharmacology and Experimental Therapeutics 295 (1): 352–9. PMID 10992001.
- Bamigbade, T. A.; Davidson, C.; Langford, R. M.; Stamford, J. A. (1997). "Actions of tramadol, its enantiomers and principal metabolite, O-desmethyltramadol, on serotonin (5-HT) efflux and uptake in the rat dorsal raphe nucleus". British journal of anaesthesia 79 (3): 352–356. doi:10.1093/bja/79.3.352. PMID 9389855.
- Driessen, B; Reimann, W; Giertz, H (1993). "Effects of the central analgesic tramadol on the uptake and release of noradrenaline and dopamine in vitro". British Journal of Pharmacology 108 (3): 806–11. PMC 1908052. PMID 8467366.
- Arndt, T; Claussen, U; Güssregen, B; Schröfel, S; Stürzer, B; Werle, A; Wolf, G (2011). "Kratom alkaloids and O-desmethyltramadol in urine of a "Krypton" herbal mixture consumer". Forensic science international 208 (1–3): 47–52. doi:10.1016/j.forsciint.2010.10.025. PMID 21112167.
- Bäckstrom, BG; Classon, G; Löwenhielm, P; Thelander, G (2010). "Krypton--new, deadly Internet drug. Since October 2009 have nine young persons died in Sweden". Lakartidningen 107 (50): 3196–7. PMID 21294331.
- Kronstrand, R; Roman, M; Thelander, G; Eriksson, A (2011). "Unintentional fatal intoxications with mitragynine and O-desmethyltramadol from the herbal blend Krypton". Journal of analytical toxicology 35 (4): 242–7. PMID 21513619.