Focale Drug Interactions

Drug Affecting or Metabolized by Hepatic Microsomal Enzymes: Because levetiracetam is neither a substrate nor inhibitor of cytochrome P-450 (CYP), pharmacokinetic interactions are likely with drugs affecting or metabolized by CYP isoenzymes.
Anticonvulsants: Clinically important pharmacokinetic interactions are unlikely when levetiracetam is administered concomitantly with other anticonvulsants (e.g., carbamazepine, gabapentin, lamotrigine, phenobarbital, phenytoin, valproic acid).
In pediatric patients, an approximately 22% increase in levetiracetam clearance was observed when the drug was administered concurrently with hepatic enzyme-inducing anticonvulsants (e.g., carbamazepine); however, dosage adjustment is not recommended by the manufacturer. Levetiracetam did not alter plasma concentrations of carbamazepine, lamotrigine, topiramate, or valproic acid in pediatric patients with epilepsy.
Digoxin: Levetiracetam does not appear to affect the pharmacokinetics or pharmacodynamics (e.g., cardiac rhythm effects) of digoxin; digoxin also does not affect the pharmacokinetics of levetiracetam.
Oral Contraceptives: Pharmacokinetic interactions are unlikely when levetiracetam is coadministered with oral contraceptives.
Probenecid: When levetiracetam was administered concomitantly with probenecid, no effect on levetiracetam pharmacokinetics was observed, but steady-state plasma concentrations of the principal inactive metabolite were approximately doubled due to a 60% reduction in renal clearance. The manufacturer states, however, that this effect is not clinically important.
Protein-bound Drugs: Pharmacokinetic interactions are unlikely with protein-bound drugs.
Warfarin: Levetiracetam does not appear to affect the pharmacokinetics or pharmacodynamics (e.g., prothrombin time) of warfarin; warfarin also does not affect the pharmacokinetics of levetiracetam.