Due to metronidazole absorption, interactions may be seen if used concomitantly with any of the following drugs: Alcohol: Alcohol intolerance (disulfiram-like reaction).
Oral Anticoagulants: Increase in the anticoagulant effect.
Phenytoin: Increase in phenytoin blood levels, decrease in metronidazole blood levels.
Phenobarbital: Decrease in metronidazole blood levels.
Disulfiram: CNS-related effects (eg, psychotic reactions) may occur.
Cimetidine: Metronidazole blood levels and the risk of neurologic side effects may increase.
Lithium: Increase in lithium toxicity may be observed.
Astemizole and Terfenadine: Metronidazole and miconazole inhibit the metabolism of these drugs and increase their plasma concentrations.
Interference with blood levels of liver enzymes, glucose (hexokinase method), theophylline and procainamide have been observed during treatment with metronidazole.