Prescrire international
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Prescrire international · Feb 2016
Review"Weak" opioid analgesics. Codeine, dihydrocodeine and tramadol: no less risky than morphine.
So-called weak opioid analgesics are often used to treat severe pain, or when paracetamol or a nonsteroidal anti-inflammatory drug (NSAID) proves inadequate. But are weak opioids any more effective than paracetamol or NSAIDs on nociceptive pain, and are they better tolerated than morphine? To answer these questions, we conducted a review of literature using the standard Prescrire methodology. The potency of codeine and tramadol is strongly influenced by the cytochrome P450 isoenzyme CYP2D6 genotype, which varies widely from one person to another. ⋯ There is also a sometimes unpredictable risk of serious over-dose. Tramadol has additional adverse effects unrelated to its opioid effects. Weak opioids require at least as much vigilance as morphine, despite the major differences in their reputation and regulation.