Fomepizole dosing maintenance after the loading dose?

• A. 5 mg/kg IV every 6 hours.
• B. 20 mg/kg IV every 24 hours.
• C. 10 mg/kg IV every 12 hours.
• D. 15 mg/kg IV every 24 hours.

Answer: (C)

Fomepizole inhibits alcohol dehydrogenase, blocking the conversion of methanol and ethylene glycol to their toxic metabolites. After you give the loading dose to rapidly achieve enzyme inhibition, you need a maintenance dose to keep that inhibition as the toxin is cleared. The standard maintenance plan is 10 mg/kg IV every 12 hours, which sustains effective enzyme blockade without allowing levels to drop and permit toxic metabolism again. The other schedules either underdose per dose or space the doses too far apart, risking periods of inadequate inhibition. So, 10 mg/kg IV every 12 hours best maintains continuous inhibition after the loading dose.