Drug Interactions between ezogabine and metronidazole

CONTRAINDICATED: Use of alcohol or products containing alcohol during nitroimidazole therapy may result in a disulfiram-like reaction in some patients. There have been a few case reports involving metronidazole, although data overall are not convincing. The presumed mechanism is inhibition of aldehyde dehydrogenase (ALDH) by metronidazole in a manner similar to disulfiram. Following ingestion of alcohol, inhibition of ALDH results in increased concentrations of acetaldehyde, the accumulation of which can produce an unpleasant physiologic response referred to as the 'disulfiram reaction'. Symptoms include flushing, throbbing in head and neck, throbbing headache, respiratory difficulty, nausea, vomiting, sweating, thirst, chest pain, palpitation, dyspnea, hyperventilation, tachycardia, hypotension, syncope, weakness, vertigo, blurred vision, and confusion. Severe reactions may result in respiratory depression, cardiovascular collapse, arrhythmia, myocardial infarction, acute congestive heart failure, unconsciousness, convulsions, and death. However, some investigators have questioned the disulfiram-like properties of metronidazole. One study found neither elevations in blood acetaldehyde nor objective or subjective signs of a disulfiram-like reaction to ethanol in six subjects treated with metronidazole (200 mg three times a day for 5 days) compared to six subjects who received placebo.

MANAGEMENT: Because clear evidence is lacking concerning the safety of ethanol use during nitroimidazole therapy, patients should be apprised of the potential for interaction. Consumption of alcoholic beverages and products containing propylene glycol is specifically contraindicated during and for at least 3 days after completion of metronidazole and benznidazole therapy according to their product labeling.

GENERALLY AVOID: Alcohol may increase the plasma concentrations of ezogabine. In a study of healthy volunteers, the administration of ezogabine 200 mg in combination with ethanol 1g/kg (5 standard alcohol drinks) over 20 minutes resulted in an increase in the ezogabine peak plasma concentration (Cmax) and systemic exposure (AUC) by 23% and 37%, respectively.

Food does not significantly affect the bioavailability of ezogabine. According to the product labeling, high-fat food does not affect the extent to which ezogabine is absorbed, but increases peak plasma concentration (Cmax) by approximately 38% and delays the time to reach peak concentration (Tmax) by 0.75 hour.

MANAGEMENT: In general, alcohol consumption should be avoided or limited during treatment with CNS-depressant agents. Patients should be advised of the potential for increased dose-related adverse reactions of ezogabine (e.g., dizziness, somnolence, nausea, constipation, urinary retention, blurred vision, memory impairment, tremor) when taken with alcohol, and to avoid hazardous activities that require mental alertness and motor coordination until they know how the medication affects them. Ezogabine can be taken with or without food.