Levetiracetam, a new antiepileptic agent: lack of in vitro and in vivo pharmacokinetic interaction with valproic acid.
OBJECTIVE
The novel antiepileptic drug (AED) levetiracetam (LEV; Keppra) has a wide therapeutic index and pharmacokinetic characteristics predicting limited drug-interaction potential. It is indicated as an add-on treatment in patients with epilepsy, and thus coadministration with valproic acid (VPA) is likely. These studies were performed to determine whether coadministration of LEV with VPA might result in pharmacokinetic interactions.


METHODS
In vitro assays were performed to characterize the transformation of LEV into its main in vivo metabolite UCB L057. The reaction was examined for its sensitivity to clinically relevant concentrations of VPA. An open-label, one-way, one-sequence crossover clinical trial was conducted in 16 healthy volunteers to assess further the possibility of any relevant pharmacokinetic interaction.


RESULTS
Human whole blood and, to a lesser extent, human liver homogenates were demonstrated to hydrolyze LEV to UCB L057, its main metabolite. The reaction possibly involves type-B esterases and is not affected by 1 mM VPA (i.e., 166 microg/ml). Pharmacokinetic parameters of a single dose of LEV (1,500 mg) coadministered with steady-state concentrations of VPA (8 days of 500 mg, b.i.d.) did not differ significantly from the pharmacokinetics of LEV administered alone [area under the curve (AUC) of 397 and 400 microg/h/ml, respectively]. Furthermore, LEV did not affect the steady-state pharmacokinetics of VPA.


CONCLUSIONS
These findings suggest the absence of a pharmacokinetic interaction between VPA and LEV during short-term administration, and suggest that dose adjustment is not required when these two drugs are given together.
Coupez
René
R
UCB S.A. Pharma Sector, and the Brain Center, Brussels, Belgium.
Nicolas
Jean-Marie
JM
Browne
Thomas R
TR
D000328:Adult; D000927:Anticonvulsants / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D001682:Biological Availability; D001711:Biotransformation; D018592:Cross-Over Studies; D003692:Delayed-Action Preparations; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004353:Drug Evaluation, Preclinical; D004347:Drug Interactions; D005260:Female; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D000077287:Levetiracetam; D008099:Liver / Q000201:enzymology; D008297:Male; D008657:Metabolic Clearance Rate / Q000502:physiology; D008875:Middle Aged; D010889:Piracetam / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000493:pharmacokinetics*; D012697:Serine Endopeptidases / Q000502:physiology; D014635:Valproic Acid / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*
D000927:Anticonvulsants; D003692:Delayed-Action Preparations; D000077287:Levetiracetam; D014635:Valproic Acid; D012697:Serine Endopeptidases; C049262:esterase B; D010889:Piracetam