Comparison with related substances
Structurally, Tapentadol is the closest chemical relative of tramadol in clinical use. Tapentadol is also an opioid, but unlike both tramdol and venlafaxine, tapentadol represents only one stereoisomer (the weaker of the two, in terms of opioid effect). Both tramadol and venlafaxine are racemic mixtures. Structurally, tapentadol also differs from tramadol in being a phenol, and not an ether. Also, both tramadol and venlafaxine incorporate a cyclohexyl moiety, attached directly to the aromatic, whilst tapentadol lacks this feature. In reality, the closest structural chemical entity (to tapentadol) in clinical use, is the OTC active, phenylephrine. Both share a meta phenol, attached to straight chain hydrocarbon. And in both cases, the hydrocarbon terminates in an amine. Tapentadol differs from phenylephrine in several major ways, however. First, tapentadol appears to be an efficacious analgesic, whilst phenylephrines absolute efficacy is a serious concern. Tapentadol is a scheduleII narcotic in the US, while phenylephrine is considered a politically correct alternative to the safe and effective pseudoephedrine. Phenylephrine is effective in shrinking small capillaries locally, but is inferior to pseudoephedrine as a nasal decongestant
The chemical synthesis of tramadol is described in the literature. Tramadol [2-(dimethylaminomethyl)-1-(3-methoxyphenyl)cyclohexanol] has two stereogenic centers at the cyclohexane ring. Thus, 2-(dimethylaminomethyl)-1-(3-methoxyphenyl)cyclohexanol may exist in four different configurational forms:
The synthetic pathway leads to the racemate (1:1 mixture) of (1R,2R)-isomer and the (1S,2S)-isomer as the main products. Minor amounts of the racemic mixture of the (1R,2S)-isomer and the (1S,2R)-isomer are formed as well. The isolation of the (1R,2R)-isomer and the (1S,2S)-isomer from the diastereomeric minor racemate [(1R,2S)-isomer and (1S,2R)-isomer] is realized by the recrystallization of the hydrochlorides. The drug tramadol is a racemate of the hydrochlorides of the (1R,2R)-(+)- and the (1S,2S)-(–)-ennntiomers. The resolution of the racemate [(1R,2R)-(+)-isomer / (1S,2S)-(–)-isomer] was described employing (R)-(–)- or (S)-(+)-mandelic acid. This process does not find industrial application, since tramadol is used as a racemate, besides known different physiological effects  of the (1R,2R)- and (1S,2S)-isomers.
- Tramadol Information for Consumers
- Tramadol Information for Healthcare Professionals (includes dosage details)
- Side Effects of Tramadol (detailed)
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