Drug Interactions between eletriptan and netupitant / palonosetron

MONITOR CLOSELY: Concomitant use of 5-HT3 receptor antagonists with agents that possess or enhance serotonergic activity such as selective serotonin reuptake inhibitors (SSRIs), selective serotonin-norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), 5-HT1 receptor agonists (triptans), ergot alkaloids, phenylpiperidine opioids, bupropion, dextromethorphan, linezolid, lithium, St. John's wort, tramadol, and tryptophan may potentiate the risk of serotonin syndrome, which is a rare but serious and potentially fatal condition thought to result from hyperstimulation of brainstem 5-HT1A and 2A receptors. According to the manufacturers, development of serotonin syndrome has been reported with 5-HT3 receptor antagonists, primarily during concomitant use of serotonergic drugs but also in overdose. Some of the reported cases were fatal. Symptoms of the serotonin syndrome may include mental status changes such as irritability, altered consciousness, confusion, hallucination, and coma; autonomic dysfunction such as tachycardia, hyperthermia, diaphoresis, shivering, blood pressure lability, and mydriasis; neuromuscular abnormalities such as hyperreflexia, myoclonus, tremor, rigidity, and ataxia; and gastrointestinal symptoms such as abdominal cramping, nausea, vomiting, and diarrhea.

MANAGEMENT: Caution is advised if 5-HT3 receptor antagonists are prescribed with other agents that affect the serotonergic neurotransmitter system. Patients should be closely monitored for symptoms of the serotonin syndrome during treatment. Particular caution is warranted when initiating or increasing the dosages of these agents. The potential risk for serotonin syndrome should be considered even when administering serotonergic agents sequentially, as some agents may demonstrate a prolonged elimination half-life. For example, a 5-week washout period is typically recommended following use of fluoxetine and 2 weeks following use of MAOIs before administering another serotonergic agent. If serotonin syndrome develops or is suspected during the course of therapy, all serotonergic agents should be discontinued immediately and supportive care rendered as necessary. Moderately ill patients may also benefit from the administration of a serotonin antagonist (e.g., cyproheptadine, chlorpromazine). Severe cases should be managed under consultation with a toxicologist and may require sedation, neuromuscular paralysis, intubation, and mechanical ventilation in addition to the other measures.

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MONITOR: Coadministration with inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of eletriptan, which is primarily metabolized by the isoenzyme. According to the product labeling, eletriptan peak plasma concentration (Cmax) and systemic exposure (AUC) increased by nearly 3-fold and 6-fold, respectively, during coadministration with the potent inhibitor ketoconazole (400 mg). Likewise, erythromycin (1000 mg) increased eletriptan Cmax by 2-fold and AUC by nearly 4-fold. The half-life of eletriptan increased from about 5 hours to 8 hours with ketoconazole and 7 hours with erythromycin. Verapamil (480 mg), a moderate CYP450 3A4 inhibitor, increased eletriptan Cmax by 2.2-fold and AUC by 2.7-fold, while fluconazole (100 mg), a relatively weak inhibitor, increased eletriptan Cmax by 1.4-fold and AUC by 2-fold. Clinically, this interaction may result in increased risk of vasospastic reactions associated with the use of 5-HT1 receptor agonists, such as coronary artery vasospasm, peripheral vascular ischemia, and colonic ischemia.

MANAGEMENT: Eletriptan should not be used within at least 72 hours of treatment with potent CYP450 3A4 inhibitors such as itraconazole, ketoconazole, nefazodone, delavirdine, most protease inhibitors, and ketolide and certain macrolide antibiotics. The manufacturer makes no specific recommendations for use with less potent inhibitors, but caution is appropriate. Patients should have vital signs monitored regularly and advised to notify their physician if they experience signs and symptoms of vasospasm such as numbness, tingling, or cyanosis in the extremities; muscle pains; weakness; or chest pain or tightness. Alternatively, other 5-HT1 receptor agonists that are not metabolized by CYP450 3A4 may be considered, such as frovatriptan, naratriptan, rizatriptan, sumatriptan, and zolmitriptan.

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