Phenytoin Toxicity with High Dose, Concomitant Ascorbic Acid Dosing.

Area of Science:

• Pharmacology
• Clinical Toxicology
• Neurology

Background:

• Phenytoin is a widely used antiepileptic drug.
• Ascorbic acid (vitamin C) is a common supplement.
• Interactions between high-dose ascorbic acid and phenytoin are not well-established.

Purpose of the Study:

• To report a case of potential phenytoin toxicity due to concomitant high-dose ascorbic acid administration.
• To describe the adverse drug reactions observed in this patient.
• To inform clinicians about a possible drug interaction.

Main Methods:

• Case report detailing a patient's clinical course.
• Observation of phenytoin levels and adverse events.
• Discontinuation of interacting medications and initiation of alternative treatment.

Main Results:

• Concomitant use of high-dose ascorbic acid with phenytoin led to elevated phenytoin levels.
• The patient experienced adverse drug reactions including truncal ataxia and weakness.
• Discontinuation of ascorbic acid and phenytoin, followed by lacosamide and gabapentin, resolved symptoms.

Conclusions:

• High-dose ascorbic acid may potentiate phenytoin toxicity.
• Clinicians should exercise caution when prescribing high-dose ascorbic acid to patients on phenytoin.
• Monitoring of phenytoin levels and potential adverse effects is crucial in such cases.