UMEM Educational Pearls

Category: Neurology

Title: Phenytoin and Phenobarbital Toxicity

Keywords: phenytoin, phenbarbital, dilantin (PubMed Search)

Posted: 9/2/2009 by Aisha Liferidge, MD (Updated: 12/5/2021)
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  • The therapeutic ranges for phenytoin (dilantin) and phenobarbital in adults are 10 to 20 mcg/mL and 10 to 30 mcg/mL, respectively.
  • Phenytoin plasma levels rise more rapidly than phenobarbital levels; therefore, an acute overdose of the two together will likely manifest as phenytoin toxicity before phenobarbital toxicity.
  • Phenytoin has a more narrow margin between therapeutic and toxic levels than does phenobarbital.