Drug Interactions between DDAVP Nasal and levomethadyl acetate

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.

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Food may decrease the rate and extent of absorption of desmopressin following oral administration. In 16 healthy, nonsmoking volunteers, administration of a single 400 mcg oral dose of desmopressin concomitantly with a standardized meal (27% fat) resulted in a 52% decrease in the peak plasma concentration (Cmax) of desmopressin and a 43% decrease in systemic exposure (AUC) compared to administration in the fasting state. The Cmax and AUC were still reduced by 46% and 41%, respectively, when desmopressin was administered 1.5 hours after eating. Both feeding regimens prolonged the time to reach peak plasma concentration (Tmax) from 1 hour to 1.5 hours. However, the pharmacodynamic effects of desmopressin were not affected as assessed by urine volume and osmolality for at least 4 hours postdose. The degree of antidiuresis was similar in the absence of food and when the drug was taken with or 1.5 hours after eating. These findings would suggest a fairly minor clinical impact of the interaction in most patients, especially since oral desmopressin is intended for administration at bedtime. Nevertheless, the possibility of food effects should be considered before increasing the dose whenever a diminution of effect is noted. A significant interaction is not expected to occur with the sublingual formulation, since absorption occurs primarily in the oral mucosa, pharynx, and esophagus.

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