Drug Interactions between levomethadyl acetate and sodium oxybate

GENERALLY AVOID: The concurrent use of levomethadyl acetate and alcohol may result in additive CNS and respiratory depression, hypotension, sedation, or coma. Grapefruit juice may increase the plasma concentrations of orally administered drugs which are substrates of the CYP450 3A4 isoenzyme, such as levomethadyl acetate. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. The extent and clinical significance are unknown. Moreover, pharmacokinetic alterations associated with interactions involving grapefruit juice are often subject to a high degree of interpatient variability.

MANAGEMENT: Patients who are known to abuse alcohol should be warned of the risk of potentially fatal overdose if these substances are taken concurrently. Patients who regularly consume grapefruits and grapefruit juice should be monitored for adverse effects and altered plasma concentrations of levomethadyl acetate. A 12-lead ECG should be performed before initiating therapy, 12 to 14 days after initiating therapy, and periodically thereafter. Patients should be advised to immediately seek medical attention if they experience palpitations, dizziness, lightheadedness, fainting, or seizures. Grapefruits and grapefruit juice should be avoided if an interaction is suspected. Orange juice is not expected to interact.

CONTRAINDICATED: Alcohol may potentiate the central nervous system and respiratory depressant effects of sodium oxybate, which is the sodium salt of gamma hydroxybutyrate (GHB). An increased risk of serious adverse reactions such as respiratory depression, hypotension, profound sedation, syncope, coma, and even death should be anticipated.

ADJUST DOSING INTERVAL: Food may delay the absorption and significantly decrease the bioavailability of sodium oxybate. When sodium oxybate was administered immediately after a high-fat meal, the time to reach peak plasma concentration (Tmax) increased from 0.75 hour to 2 hours, the peak plasma concentration (Cmax) decreased by a mean of 59%, and the systemic exposure (AUC) decreased by a mean of 37%.

MANAGEMENT: The concomitant use of sodium oxybate with alcohol is considered contraindicated. The first dose of sodium oxybate should be taken at least 2 hours after a meal to ensure maximal absorption.