Drug Interactions between Caduet 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: Coadministration with grapefruit juice may increase the plasma concentrations of atorvastatin. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. When a single 40 mg dose of atorvastatin was coadministered with 240 mL of grapefruit juice, atorvastatin peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 16% and 37%, respectively. Greater increases in Cmax (up to 71%) and/or AUC (up to 2.5 fold) have been reported with excessive consumption of grapefruit juice (>=750 mL to 1.2 liters per day). Clinically, high levels of HMG-CoA reductase inhibitory activity in plasma is associated with an increased risk of musculoskeletal toxicity. Myopathy manifested as muscle pain and/or weakness associated with grossly elevated creatine kinase exceeding ten times the upper limit of normal has been reported occasionally. Rhabdomyolysis has also occurred rarely, which may be accompanied by acute renal failure secondary to myoglobinuria and may result in death.

ADJUST DOSING INTERVAL: Fibres such as oat bran and pectin may diminish the pharmacologic effects of HMG-CoA reductase inhibitors by interfering with their absorption from the gastrointestinal tract.

MANAGEMENT: Patients receiving therapy with atorvastatin should limit their consumption of grapefruit juice to no more than 1 liter per day. Patients should be advised to promptly report any unexplained muscle pain, tenderness or weakness, particularly if accompanied by fever, malaise and/or dark colored urine. Therapy should be discontinued if creatine kinase is markedly elevated in the absence of strenuous exercise or if myopathy is otherwise suspected or diagnosed. In addition, patients should either refrain from the use of oat bran and pectin or, if concurrent use cannot be avoided, to separate the administration times by at least 2 to 4 hours.

MONITOR: Many psychotherapeutic and CNS-active agents (e.g., anxiolytics, sedatives, hypnotics, antidepressants, antipsychotics, opioids, alcohol, muscle relaxants) exhibit hypotensive effects, especially during initiation of therapy and dose escalation. Coadministration with antihypertensives and other hypotensive agents, in particular vasodilators and alpha-blockers, may result in additive effects on blood pressure and orthostasis.

MANAGEMENT: Caution and close monitoring for development of hypotension is advised during coadministration of these agents. Some authorities recommend avoiding alcohol in patients receiving vasodilating antihypertensive drugs. Patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia. Patients should also avoid driving or operating hazardous machinery until they know how the medications affect them.

MONITOR: Calcium-containing products may decrease the effectiveness of calcium channel blockers by saturating calcium channels with calcium. Calcium chloride has been used to manage acute severe verapamil toxicity.

MANAGEMENT: Management consists of monitoring the effectiveness of calcium channel blocker therapy during coadministration with calcium products.

The consumption of grapefruit juice may slightly increase plasma concentrations of amlodipine. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. Data have been conflicting and the clinical significance is unknown. Monitoring for calcium channel blocker adverse effects (e.g., headache, hypotension, syncope, tachycardia, edema) is recommended.