Drug Interactions between Lithium Carbonate ER and sodium phenylbutyrate

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.

ADJUST DOSING INTERVAL: Coadministration with a high-fat meal may reduce the rate and extent of absorption of sodium phenylbutyrate. When a single 3 g-1 g dose of sodium phenylbutyrate-taurursodiol (sodium phenylbutyrate-ursodoxicoltaurine) was administered to healthy volunteers in the presence of a high-fat, high-calorie meal (approximately 800 to 1000 calories; 500 to 600 calories from fat, 250 calories from carbohydrate, 150 calories from protein), sodium phenylbutyrate peak plasma concentration (Cmax) decreased by 75% and systemic exposure (AUC) decreased by 55%. The Cmax for taurursodiol was not significantly affected, but AUC was increased by 46%. The clinical significance of these changes has not been established. In premarketing studies, patients were advised to take the drug before a meal.

MANAGEMENT: The prescribing information recommends administration of sodium phenylbutyrate-taurursodiol before a meal or snack, particularly in patients of low body weight (less than 70 kg).

MONITOR: One study has suggested that caffeine withdrawal may significantly increase blood lithium levels. The mechanism may be involve reversal of a caffeine-induced increase in renal lithium excretion.

MANAGEMENT: When caffeine is eliminated from the diet of lithium-treated patients, caution should be exercised. When caffeine consumption is decreased, close observation for evidence of lithium toxicity and worsening of the psychiatric disorder is recommended. Patients should be advised to notify their physician if they experience symptoms of possible lithium toxicity such as drowsiness, dizziness, weakness, ataxia, tremor, vomiting, diarrhea, thirst, blurry vision, tinnitus, or increased urination.