Drug Interactions between bupropion / dextromethorphan and cyclosporine

GENERALLY AVOID: Administration with grapefruit juice (compared to water or orange juice) has been shown to increase blood concentrations of cyclosporine with a relatively high degree of interpatient variability. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits.

GENERALLY AVOID: Administration with red wine or purple grape juice may decrease blood concentrations of cyclosporine. In 12 healthy volunteers, 12 ounces total of a merlot consumed 15 minutes prior to and during cyclosporine administration (single 8 mg/kg dose of Sandimmune) decreased cyclosporine peak blood concentration (Cmax) and systemic exposure (AUC) by 38% and 30%, respectively, compared to water. The time to reach peak concentration (Tmax) doubled, and oral clearance increased 50%. Similarly, one study were 12 healthy patients were administered purple grape juice and a single dose of cyclosporine showed a 30% and a 36% decrease in cyclosporine systemic exposure (AUC) and peak blood concentration (Cmax), respectively. The exact mechanism of interaction is unknown but may involve decreased cyclosporine absorption.

MONITOR: Food has been found to have variable effects on the absorption of cyclosporine. There have been reports of impaired, unchanged, and enhanced absorption during administration with meals relative to the fasting state. The mechanisms are unclear. Some investigators found an association with the fat content of food. In one study, increased fat intake resulted in significantly increased cyclosporine bioavailability and clearance. However, the AUC and pharmacodynamics of cyclosporine were not significantly affected, thus clinical relevance of these findings may be minimal.

MANAGEMENT: Patients receiving cyclosporine therapy should be advised to either refrain from or avoid fluctuations in the consumption of grapefruits and grapefruit juice. Until more data are available, the consumption of red wine or purple grape juice should preferably be avoided or limited. All oral formulations of cyclosporine should be administered on a consistent schedule with regard to time of day and relation to meals so as to avoid large fluctuations in plasma drug levels.

GENERALLY AVOID: Excessive use or abrupt discontinuation of alcohol after chronic ingestion may precipitate seizures in patients receiving bupropion. Additionally, there have been rare postmarketing reports of adverse neuropsychiatric events or reduced alcohol tolerance in patients who drank alcohol during treatment with bupropion. According to one forensic report, a patient died after taking large doses of both bupropion and alcohol. It is uncertain whether a drug interaction was involved. Single-dose studies in healthy volunteers given bupropion and alcohol failed to demonstrate either a significant pharmacokinetic or pharmacodynamic interaction.

MANAGEMENT: The manufacturer recommends that alcohol consumption be minimized or avoided during bupropion treatment. The use of bupropion is contraindicated in patients undergoing abrupt discontinuation of alcohol.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

MONITOR: Additive or synergistic effects on blood pressure may occur when bupropion is combined with sympathomimetic agents such as nasal decongestants, adrenergic bronchodilators, ophthalmic vasoconstrictors, and systemic vasopressors. Treatment with bupropion can result in elevated blood pressure and hypertension. In clinical practice, hypertension, in some cases severe and requiring acute treatment, has been observed in patients receiving bupropion alone and in combination with nicotine replacement therapy. These events have occurred in both patients with and without evidence of preexisting hypertension. Furthermore, postmarketing cases of hypertensive crisis have been reported during the initial titration phase with bupropion-naltrexone treatment.

MANAGEMENT: Caution is advised when bupropion is used with other drugs that increase dopaminergic or noradrenergic activity due to an increased risk of hypertension. Blood pressure and heart rate should be measured prior to initiating bupropion therapy and monitored at regular intervals consistent with usual clinical practice, particularly in patients with preexisting hypertension. Dose reduction or discontinuation of bupropion should be considered in patients who experience clinically significant and sustained increases in blood pressure or heart rate.

MONITOR: The concomitant use of bupropion and nicotine replacement for smoking cessation may increase the risk of hypertension. In a clinical study (n=250), 6.1% of patients who used sustained-release bupropion with nicotine transdermal system developed treatment-emergent hypertension, compared to 2.5% of patients treated with bupropion alone, 1.6% treated with nicotine alone, and 3.1% treated with placebo. Three patients in the bupropion plus nicotine group and one patient in the nicotine-only group discontinued treatment due to hypertension. The majority had evidence of preexisting hypertension.

MANAGEMENT: Blood pressure monitoring is recommended for patients concomitantly using bupropion and nicotine replacement for smoking cessation.