Phenytoin-misonidazole: possible metabolic interaction

Area of Science:

• Pharmacology
• Clinical Pharmacy

Background:

• Misonidazole is an investigational drug.
• Phenytoin is an anti-epileptic drug with a narrow therapeutic index.

Purpose of the Study:

• To investigate the pharmacokinetic interaction between misonidazole and phenytoin.

Main Methods:

• Intravenous administration of misonidazole.
• Observation of misonidazole plasma half-life and metabolism in a patient on chronic phenytoin therapy.

Main Results:

• Misonidazole exhibited a significantly decreased plasma half-life (3.8 hours) in the patient receiving phenytoin, compared to controls (9.1 hours +/- 0.8).
• Increased metabolism of misonidazole was observed in the patient on phenytoin therapy.

Conclusions:

• Continuous phenytoin therapy may alter the pharmacokinetics of misonidazole.
• Phenytoin may increase the metabolism of misonidazole, leading to a reduced half-life.