A. Displaces sulfonamides from plasma proteins B. Drug of choice in myoclonic seizures C. Half-life is increased if used with phenobarbital D. Isoniazid decreases steady-state blood levels of phenytoin E. Toxic effects may occur with only small increments in dose
Toxic effects may occur with only small increments in dose
Sulfonamides can displace phenytoin from its binding sites, increasing the plasma-free fraction of the drug. Induction of liver drug-metabolizing enzymes by phenobarbital results in a decreased half-life of phenytoin, and isoniazid increases plasma levels of phenytoin by inhibiting its metabolism. Because of the dose-dependent elimination kinetics of phenytoin, some toxicity may occur with only small increments in dose.