Drug Interactions between bupivacaine / ketamine / ketorolac and lixisenatide

MONITOR CLOSELY: Coadministration of ketamine with other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. In addition, opioid analgesics, barbiturates, and benzodiazepines may prolong the time to complete recovery from anesthesia.

MANAGEMENT: During concomitant use of ketamine with other CNS depressants, including alcohol, close monitoring of neurologic status and respiratory parameters, including respiratory rate and pulse oximetry, is recommended. Dosage adjustments should be considered according to the patient's clinical situation. Ambulatory patients should be counseled to avoid hazardous activities requiring 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.

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

GENERALLY AVOID: Coadministration of oral ketamine with grapefruit juice may significantly increase the plasma concentrations of S(+) ketamine, the dextrorotatory enantiomer of ketamine. 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. When a single 0.2 mg/kg dose of S(+) ketamine was administered orally on study day 5 with grapefruit juice (200 mL three times daily for 5 days) in 12 healthy volunteers, mean S(+) ketamine peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 2.1- and 3.0-fold, respectively, compared to administration with water. In addition, the elimination half-life of S(+) ketamine increased by 24% with grapefruit juice, and the ratio of the main metabolite norketamine to ketamine was decreased by 57%. The pharmacodynamics of ketamine were also altered by grapefruit juice. Specifically, self-rated relaxation was decreased and performance in the digit symbol substitution test was increased with grapefruit juice, but other behavioral or analgesic effects were not affected.

MANAGEMENT: Patients receiving ketamine should not drink alcohol. Caution is advised when ketamine is used in patients with acute alcohol intoxication or a history of chronic alcoholism. Following anesthesia with ketamine, patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination, such as driving or operating hazardous machinery, for at least 24 hours and until they know how the medication affects them. Patients treated with oral ketamine should also avoid consumption of grapefruit and grapefruit juice during treatment. Otherwise, dosage reductions of oral ketamine should be considered.

ADJUST DOSING INTERVAL: Lixisenatide slows gastric emptying, which may impact the absorption of concomitantly administered oral medications. The interaction has been studied with various medications, which demonstrated primarily an effect on the rate rather than the overall extent of absorption.

Acetaminophen: When acetaminophen 1000 mg was administered 1 hour and 4 hours after lixisenatide 10 mcg injection, acetaminophen peak plasma concentration (Cmax) was decreased by 29% and 31%, respectively; and median time to peak plasma concentration (Tmax) was delayed by 2 hours and 1.75 hours, respectively. The Cmax and Tmax of acetaminophen were not significantly altered when acetaminophen was given one hour before lixisenatide injection, and systemic exposure (AUC) was not affected whether administered before or after lixisenatide administration. Based on these results, no dose adjustment for acetaminophen is required; however, it may be advisable to take acetaminophen at least one hour before lixisenatide if a rapid onset of action is required.

Oral Contraceptives: When an oral contraceptive containing ethinyl estradiol 0.03 mg and levonorgestrel 0.15 mg was administered 1 hour and 4 hours after lixisenatide 10 mcg injection, ethinyl estradiol Cmax was decreased by 52% and 39%, respectively, while levonorgestrel Cmax was decreased by 46% and 20%, respectively. Median Tmax values were delayed by 1 to 3 hours, but overall exposure (AUC) and mean terminal half-life (T1/2) of ethinyl estradiol and levonorgestrel were not significantly altered. Administration of the oral contraceptive 1 hour before or 11 hours after lixisenatide had no effect on any of the measured pharmacokinetic parameters of either ethinyl estradiol or levonorgestrel. Based on these results, no dose adjustment for oral contraceptives is required; however, some authorities recommend that oral contraceptives be administered at least 1 hour before or 11 hours after lixisenatide.

Atorvastatin: When atorvastatin 40 mg and lixisenatide 20 mcg were coadministered in the morning for 6 days, atorvastatin Cmax was decreased by 31% and Tmax was delayed by 3.25 hours, but AUC was not affected. When atorvastatin was administered in the evening and lixisenatide in the morning, the AUC and Cmax of atorvastatin were increased by 27% and 66%, respectively, but there was no change in Tmax. Based on these results, no dose adjustment for atorvastatin is required; however, some authorities recommend that atorvastatin be administered at least 1 hour before lixisenatide.

Warfarin: When warfarin 25 mg was coadministered with repeated dosing of lixisenatide 20 mcg, warfarin Cmax was decreased by 19% and Tmax was delayed by 7 hours, but there were no effects on AUC or International Normalized Ratio (INR). Based on these results, no dose adjustment for warfarin is required; however, closer monitoring of INR may be appropriate following initiation or discontinuation of lixisenatide treatment.

Digoxin: When digoxin 0.25 mg and lixisenatide 20 mcg were coadministered at steady state, digoxin Cmax was decreased by 26% and Tmax was delayed by 1.5 hours, but AUC was not affected. Based on these results, no dose adjustment for digoxin is required.

Ramipril: When ramipril 5 mg and lixisenatide 20 mcg were coadministered for 6 days, ramipril Cmax was decreased by 63% and AUC was increased by 21%, while Cmax and AUC of the active metabolite (ramiprilat) were not affected. The Tmax values of ramipril and ramiprilat were delayed by approximately 2.5 hours. Based on these results, no dose adjustment for ramipril is required.

MANAGEMENT: Caution is advised during concomitant use of lixisenatide with oral medications that have a narrow therapeutic index or that require careful clinical monitoring. These medications should be administered on a consistent schedule relative to lixisenatide, and blood levels and/or pharmacologic effects should be closely monitored. In addition, if they are to be administered with food, patients should be advised to take them with a meal or snack when lixisenatide is not administered. Oral medications that are particularly dependent on threshold concentrations for efficacy, such as antibiotics, or medications for which a delay in effect is undesirable, such as acetaminophen, should be administered at least 1 hour before lixisenatide. Gastro-resistant formulations containing substances sensitive to stomach degradation should be administered 1 hour before or 4 hours after lixisenatide. Patients taking oral contraceptives should be advised to take them at least 1 hour before or 11 hours after lixisenatide.

GENERALLY AVOID: The concurrent use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol may lead to gastrointestinal (GI) blood loss. The mechanism may be due to a combined local effect as well as inhibition of prostaglandins leading to decreased integrity of the GI lining.

MANAGEMENT: Patients should be counseled on this potential interaction and advised to refrain from alcohol consumption while taking aspirin or NSAIDs.