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The hypoalgesic effect of tramadol in relation to CYP2D6*

1996; Wiley; Volume: 60; Issue: 6 Linguagem: Inglês

10.1016/s0009-9236(96)90211-8

1532-6535

Lars K. Poulsen, Lars Arendt‐Nielsen, Kim Brøsen, Søren H. Sindrup,

Pain Mechanisms and Treatments

Tramadol inhibits norepinephrine reuptake, stimulates serotonin release, and acts with μ-opioid receptors by way of its metabolite (+)-M1. Formation of M1 seems to depend on the genetic polymorphic CYP2D6. The analgesic effect of 2 mg/kg tramadol was evaluated in 15 extensive and 12 poor metabolizers of sparteine in two parallel, randomized, double-blind, placebo-controlled crossover studies that used experimental pain models. In extensive metabolizers, tramadol increased pressure pain detection (p = 0.03) and tolerance (p = 0.06) thresholds, as well as thresholds for eliciting nociceptive reflexes, after single (p = 0.0002) and repeated (p = 0.06) stimulation of the sural nerve. Peak pain and pain area in the cold pressor test were reduced (p = 0.0006 and 0.0009). In poor metabolizers, only thresholds to pressure pain tolerance (p = 0.02) and nociceptive reflexes after single stimulation (p = 0.04) were increased and the reflex threshold was less increased in poor metabolizers than in extensive metabolizers (p = 0.02). The serum concentration of (+)-M1 2 to 10 hours after tramadol ranged from 10 to 100 ng/L in extensive metabolizers, whereas in poor metabolizers serum concentrations of (+)-M1 were below or around the detection limit of 3 ng/ml. It is concluded that formation of (+)-M1 by way of CYP2D6 is important for the effect of tramadol on experimental pain. Clinical Pharmacology & Therapeutics (1996) 60, 636–644; doi: