DRUG INTERACTIONS
CYP2D6 and CYP3A4 inhibitors: Concomitant administration of CYP2D6 and/or CYP3A4 inhibitors (see
CLINICAL PHARMACOLOGY, Pharmacokinetics), such as quinidine, fluoxetine, paroxetine and amitriptyline (CYP2D6 inhibitors), and ketoconazole and erythromycin (CYP3A4 inhibitors), may reduce metabolic clearance of tramadol increasing the risk for serious adverse events including seizures and serotonin syndrome.
Serotonergic Drugs: There have been postmarketing reports of serotonin syndrome with use of tramadol and SSRIs/SNRIs or MAOIs and α2-adrenergic blockers. Caution is advised when ULTRAM ER is coadministered with other drugs that may affect the serotonergic neurotransmitter systems, such as SSRIs, MAOIs, triptans, linezolid (an antibiotic which is a reversible non-selective MAOI), lithium, or St. John's Wort. If concomitant treatment of ULTRAM ER with a drug affecting the serotonergic neurotransmitter system is clinically warranted, careful observation of the patient is advised, particularly during treatment initiation and dose increases (see
WARNINGS, Serotonin Syndrome Risk).
Triptans: Based on the mechanism of action of tramadol and the potential for serotonin syndrome, caution is advised when ULTRAM ER is coadministered with a triptan. If concomitant treatment of ULTRAM ER with a triptan is clinically warranted, careful observation of the patient is advised, particularly during treatment initiation and dose increases (see
WARNINGS, Serotonin Syndrome Risk).
Use With Carbamazepine
Patients taking carbamazepine, a CYP3A4 inducer, may have a significantly reduced analgesic effect of tramadol. Because carbamazepine increases tramadol metabolism and because of the seizure risk associated with tramadol, concomitant administration of ULTRAM ER and carbamazepine is not recommended.
Use With Quinidine
Coadministration of quinidine with ULTRAM ER resulted in a 50-60% increase in tramadol exposure and a 50-60% decrease in M1 exposure (see
CLINICAL PHARMACOLOGY, Drug Interactions). The clinical consequences of these findings are unknown.
Use With Digoxin and Warfarin
Post-marketing surveillance of tramadol has revealed rare reports of digoxin toxicity and alteration of warfarin effect, including elevation of prothrombin times.
Potential for Other Drugs to Affect Tramadol
In vitro drug interaction studies in human liver microsomes indicate that concomitant administration with inhibitors of CYP2D6 such as fluoxetine, paroxetine, and amitriptyline could result in some inhibition of the metabolism of tramadol.
Administration of CYP3A4 inhibitors, such as ketoconazole and erythromycin, or inducers, such as rifampin and St. John's Wort, with ULTRAM ER may affect the metabolism of tramadol leading to altered tramadol exposure.
Potential for Tramadol to Affect Other Drugs
In vitro drug interaction studies in human liver microsomes indicate that tramadol has no effect on quinidine metabolism. In vitro studies indicate that tramadol is unlikely to inhibit the CYP3A4-mediated metabolism of other drugs when administered concomitantly at therapeutic doses. Tramadol is a mild inducer of selected drug metabolism pathways measured in animals.
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