Drug Interactions between exenatide and lithium

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: Exenatide slows gastric emptying and may reduce the extent and rate of absorption of concomitantly administered oral medications. When acetaminophen 1000 mg was administered simultaneously with exenatide 10 mcg and also one hour, 2 hours, and 4 hours after exenatide injection, acetaminophen systemic exposure (AUC) was decreased by 21%, 23%, 24%, and 14%, respectively; peak plasma concentration (Cmax) was decreased by 37%, 56%, 54%, and 41%, respectively; and time to peak plasma concentration (Tmax) was increased from 0.6 hours in the control period to 0.9 hours, 4.2 hours, 3.3 hours, and 1.6 hours, respectively. These values were not significantly changed when acetaminophen was given one hour before exenatide injection.

MANAGEMENT: Concomitantly administered oral medications that are dependent on threshold concentrations for efficacy (e.g., antibiotics, contraceptives) or that require rapid gastrointestinal absorption (e.g., hypnotics, pain medications) should be administered at least 1 hour before exenatide. If such medications are to be administered with food, patients should be advised to take them with a meal or snack when exenatide is not administered.

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.