<unk>  is marketed as a racemic mixture of both R- and S-stereoisomers, because the two isomers complement each other's analgesic activities. The (+)-isomer is predominantly active as an opiate with a higher affinity for the µ-opiate receptor (20 times higher affinity than the (-)-isomer). Synthesis and stereoisomerism 150x150px 150x150px (1R,2R)-tramadol (1S,2S)-tramadol 150x150px 150x150px (1R,2S)-tramadol (1S,2R)-tramadol The chemical synthesis of<unk>  is described in the literature.<unk>  has two stereogenic centers at the cyclohexane ring. Thus, may exist in four different configurational forms: * (1R,2R)-isomer * (1S,2S)-isomer * (1R,2S)-isomer * (1S,2R)-isomer 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<unk>  is a racemate of the hydrochlorides of the (1R,2R)-(+)- and the (1S,2S)-(−)-enantiomers. 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<unk>  is used as a racemate, despite known different physiological effects of the (1R,2R)- and (1S,2S)-isomers, because the racemate showed higher analgesic activity than either enantiomer in animals and in humans. Detection in biological fluids<unk>  and desmetramadol may be quantified in blood, plasma or serum to monitor for abuse, confirm a diagnosis of poisoning or assist in the forensic investigation of a sudden death. Most commercial opiate immunoassay screening tests do not cross-react significantly with<unk>  or its major metabolites, so chromatographic techniques must be used to detect and quantitate these substances. The concentration of desmetramadol in the blood or plasma of a person who has taken<unk>  is generally 10–20% those of the parent drug.
Tramadol
Tapentadol
Desmetramadol
Hydrocodone
Etodolac
Ketorolac
Oxycodone
Acetylmethadol