The American journal of managed care
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Pharmacokinetic drug-drug interactions (DDIs) involving opioid analgesics can be problematic. Opioids are widely used, have a narrow therapeutic index, and can be associated with severe toxicity. ⋯ Opioids metabolized by the drug metabolizing enzymes of the cytochrome P450 (CYP450) system (codeine, oxycodone, hydrocodone, fentanyl, tramadol, and methadone) are associated with numerous DDIs that can result in either a reduction in opioid effect or excess opioid effects. Conversely, opioids that are not metabolized by that system (morphine, oxymorphone, and hydromorphone) tend to be involved in fewer CYP450-associated pharmacokinetic DDIs.