fluoxetine and tramadol

Fluoxetine and tramadol both increase serotonergic activity: fluoxetine is a selective serotonin reuptake inhibitor (SSRI) and tramadol inhibits the reuptake of serotonin and noradrenaline. Together they can precipitate serotonin syndrome. Additionally, fluoxetine inhibits CYP2D6, the enzyme responsible for converting tramadol into its active metabolite (O-desmethyltramadol). This reduces analgesic efficacy, but also increases levels of parent tramadol, which may contribute to serotonin toxicity. Both drugs also lower the seizure threshold.

The main risk is the development of serotonin syndrome, which can manifest as agitation, confusion, hyperthermia, diaphoresis, rigidity, myoclonus, and in severe cases, rhabdomyolysis, seizures, and death. There is also an increased risk of seizures. Inhibition of CYP2D6 may lead to reduced pain relief from tramadol, potentially prompting dose escalation, which may further increase serotonergic adverse effects.

Avoid the concurrent use of fluoxetine and tramadol. Choose alternative analgesic or antidepressant drugs. If co-prescription is considered essential, use the lowest possible doses, closely monitor for signs of serotonin syndrome, and inform the patient to seek urgent help. Since fluoxetine inhibits CYP2D6 for at least 2 weeks after stopping, consider this when starting tramadol. Monitor for analgesic response, and do not increase the tramadol dose without specialist advice.

The interaction is well documented. Fluoxetine is a recognized potent CYP2D6 inhibitor and an SSRI. Tramadol is a serotonergic opioid and is metabolized by CYP2D6. Case reports and clinical studies describe serotonin syndrome with this combination and reduced formation of the active metabolite.