title: Measurement of levetiracetam drug levels to assist with seizure control and monitoring of drug interactions with other anti-epileptic medications (AEMs).
abstract: OBJECTIVE
  Levetiracetam (LEV) therapeutic range (20-40mg/L) and potential drug interactions were assessed in people with epilepsy (PWE).
  
  
  METHODS
  Fifty-two PWE had LEV and concomitant medications [carbamazepine (CBZ); valproate (VPA); lamotrigine (LTG)] blood levels measured and compared to seizure activity. Lacosamide (LCM) levels were unavailable. Adopted therapeutic ranges were: 20-40mg/L - LEV; 25-50μmol/L - total CBZ; 6-13μmol/L - free CBZ; 300-750μmol/L - total VPA; 30-75μmol/L - free VPA; and 40-60μmol/L - LTG. Seizure-freedom was assessed and patients followed for almost two years.
  
  
  RESULTS
  23 of 52 PWE (44%) used LEV monotherapy and 16/23 (70%) had 'therapeutic' LEV with 13/16 (81%) seizure-free. 29 of 52 (56%) used polytherapy and 16/29 (55%) had 'therapeutic' LEV with 7/16 (44%) seizure-free. 11 of 29 (38%) used CBZ: 4/11 (36%) had therapeutic mean LEV levels and 7/11 (64%) were seizure-free. Fourteen (48%) used VPA: 9/14 (64%) had therapeutic mean LEV levels and 8/14 (57%) were seizure-free. 13 of 29 (45%) used LTG: 8/13 (62%) had therapeutic mean LEV levels and 5/13 (38%) were seizure-free. LEV did not alter CBZ, but CBZ affected LEV. LEV elevated VPA free levels but not VPA total levels. Dosage/concentration was lowered with polytherapy.
  
  
  CONCLUSIONS
  LEV range (20-40mg/L) assisted epilepsy management and anti-epileptic medication interactions were suggested with polytherapy thus possibly explaining the impaired efficacy of LEV with polytherapy.
authors.affiliation: Strategic Health Evaluators, Sydney, New South Wales, Australia.
authors.forename: Daria
authors.initials: D
authors.lastname: Stepanova
authors.affiliation: Strategic Health Evaluators, Sydney, New South Wales, Australia; Griffith University, Gold Coast and Brisbane, Queensland, Australia; University of New South Wales, Sydney, New South Wales, Australia. Electronic address: roy@royberan.com.
authors.forename: Roy G
authors.initials: RG
authors.lastname: Beran
mesh_terms: D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000627:therapeutic use*; D002220:Carbamazepine / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004359:Drug Therapy, Combination / Q000379:methods; D005260:Female; D006801:Humans; D000077287:Levetiracetam; D008297:Male; D008875:Middle Aged; D010889:Piracetam / Q000031:analogs & derivatives* / Q000627:therapeutic use; D012640:Seizures / Q000188:drug therapy*; D014635:Valproic Acid / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D000927:Anticonvulsants; D002220:Carbamazepine; D000077287:Levetiracetam; D014635:Valproic Acid; D010889:Piracetam
keywords: Drug interaction; Epilepsy; Levetiracetam; Therapeutic monitoring