Drug Interaction Report

MONITOR: Agents with anticholinergic properties (e.g., sedating antihistamines; antispasmodics; neuroleptics; phenothiazines; skeletal muscle relaxants; tricyclic antidepressants; disopyramide) may have additive effects when used in combination. Excessive parasympatholytic effects may result in paralytic ileus, hyperthermia, heat stroke, and the anticholinergic intoxication syndrome. Peripheral symptoms of intoxication commonly include mydriasis, blurred vision, flushed face, fever, dry skin and mucous membranes, tachycardia, urinary retention, and constipation. Central symptoms may include memory loss, disorientation, incoherence, hallucinations, psychosis, delirium, hyperactivity, twitching or jerking movements, stereotypy, and seizures. Central nervous system-depressant effects may also be additively or synergistically increased when these agents are combined, especially in elderly or debilitated patients. Use of neuroleptics in combination with other neuroleptics or anticholinergic agents may increase the risk of tardive dyskinesia. In addition, some neuroleptics and tricyclic antidepressants may cause prolongation of the QT interval and theoretically, concurrent use of two or more drugs that can cause QT interval prolongation may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death.

MANAGEMENT: Caution is advised when agents with anticholinergic properties are combined, particularly in the elderly and those with underlying organic brain disease, who tend to be more sensitive to the central anticholinergic effects of these drugs and in whom toxicity symptoms may be easily overlooked. Patients should be advised to notify their physician promptly if they experience potential symptoms of anticholinergic intoxication such as abdominal pain, fever, heat intolerance, blurred vision, confusion, and/or hallucinations. Ambulatory patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them. A reduction in anticholinergic dosages may be necessary if excessive adverse effects develop.

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GENERALLY AVOID: Grapefruit juice may significantly increase the plasma concentrations of lurasidone. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Inhibition of hepatic CYP450 3A4 may also contribute. The interaction has not been studied with grapefruit juice, but has been reported for other CYP450 3A4 inhibitors. When a single 10 mg dose of lurasidone was administered with the potent CYP450 3A4 inhibitor ketoconazole (400 mg/day for 5 days), lurasidone peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 6.9- and 9.0-fold, respectively, compared to administration alone. The AUC of lurasidone's active metabolite increased by 6-fold. Another potent CYP450 3A4 inhibitor, posaconazole, has been reported to increase lurasidone AUC by approximately 4.5-fold. When a single 20 mg dose of lurasidone was administered with the moderate CYP450 3A4 inhibitor diltiazem (extended release formulation 240 mg/day for 5 days), lurasidone Cmax and AUC increased by 2.1- and 2.2-fold, respectively, while the AUC of the active metabolite increased by 2.4-fold. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition.

GENERALLY AVOID: Alcohol may potentiate some of the central nervous system and hypotensive effects of lurasidone. Use in combination may result in increased sedation, dizziness, hypotension, and impairment of judgment, thinking, and psychomotor skills.

ADJUST DOSING INTERVAL: Food increases the oral bioavailability of lurasidone. According to the product labeling, lurasidone mean Cmax and AUC were increased approximately 3-fold and 2-fold, respectively, when administered with food relative to under fasting conditions. Lurasidone AUC was not affected by meal size (in the range of 350 to 1000 calories) or fat content. In clinical studies, lurasidone was administered with food.

MANAGEMENT: Patients treated with lurasidone should avoid consumption of grapefruit and grapefruit juice as well as alcohol. Lurasidone should be taken with food (at least 350 calories).

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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.

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