Drug interactions between sibutramine and Sudafed PE Cold & Cough

GENERALLY AVOID: Concomitant use of sibutramine with other serotonin reuptake inhibitors or other agents possessing serotonergic activity such as monoamine oxidase inhibitors, tricyclic antidepressants, 5-HT1 receptor agonists, ergot alkaloids, lithium, St. John's wort, phenylpiperidine opioids, dextromethorphan, 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. Symptoms of the serotonin syndrome may include mental status changes such as irritability, altered consciousness, confusion, hallucinations, 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: In general, the concomitant use of sibutramine with other serotonergic agents should be avoided if possible, or otherwise approached with caution if potential benefit is deemed to outweigh the risk. Patients should be closely monitored for symptoms of the serotonin syndrome during treatment. Particular caution is advised when 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 recommended following use of fluoxetine before administering another serotonergic agent such as sibutramine. At least 14 days should elapse between discontinuation of other serotonergic agents and initiation of treatment with sibutramine. 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.

MONITOR: Additive or synergistic effects on blood pressure and heart rate may occur when sibutramine is combined with sympathomimetic agents such as nasal decongestants, adrenergic bronchodilators, ophthalmic vasoconstrictors, and systemic vasopressors. Sibutramine is a potent inhibitor of norepinephrine and serotonin reuptake, and a less potent inhibitor of dopamine reuptake. In placebo-controlled obesity studies, sibutramine 5 to 20 mg once daily was associated with mean increases in systolic and diastolic blood pressure of approximately 1 to 3 mmHg and mean increases in pulse rate of approximately 4 to 5 beats per minute relative to placebo. Larger increases were observed in some patients, particularly when therapy was initiated at the higher dosages. However, use in combination with sympathomimetic agents has not been formally evaluated.

MANAGEMENT: Caution is advised if sibutramine is used with other drugs that can increase blood pressure and/or heart rate. Blood pressure and pulse should be measured prior to initiating therapy with sibutramine and monitored at regular intervals thereafter. Dose reduction or discontinuation of sibutramine should be considered in patients who experience a sustained increase in blood pressure or pulse rate.