O-desmethyltramadol
What it isThe M1 metabolite of tramadol, formed by CYP2D6, and the actual mu agonist.
Why it mattersTramadol itself is a weak opioid — this metabolite provides essentially all the opioid analgesia.
What it changesIt is why CYP2D6 poor metabolizers get no analgesia and ultra-rapid metabolizers get dangerous opioid effect from a normal dose.
FDA-approved for
- pain (active metabolite of tramadol)
NO BOXED WARNINGS
Principal riskThis is why tramadol fails in CYP2D6 poor metabolizers and kills ultra-rapid metabolizers, inclu