title: Computerized tremor analysis of valproate-induced tremor: a comparative study of controlled-release versus conventional valproate.
abstract: OBJECTIVE
  Valproate (VPA) induces postural tremor in 6-45% of patients. The characteristics of VPA-induced tremor have not yet been quantitatively assessed, and it is not known whether tremor prevalence or severity is affected by VPA formulation (controlled-release CR-VPA vs. conventional VPA). The aim of this study was quantitatively to assess tremor in epilepsy patients receiving VPA and to compare the effects of two VPA formulations (CR-VPA vs. VPA) on tremor severity.
  
  
  METHODS
  In a prospective study, 18 consecutive patients with newly diagnosed focal or generalized epilepsy were assigned to receive alternately either VPA (n=10) or CR-VPA (n=8) monotherapy. Computerized tremor analysis was performed at baseline 1 day before initiating VPA treatment and repeated after a seizure-free period of >or=8 weeks, during which VPA doses had remained stable. Rest and postural tremor were recorded by accelerometry, and surface electromyograms (EMGs) were recorded from the wrist flexors and extensors.
  
  
  RESULTS
  At baseline, the two groups had similar postural tremor amplitudes. At follow-up, the CR-VPA group had remained at the same level, whereas VPA subjects exhibited a significant increase in tremor amplitudes (p<0.05) despite comparable VPA doses and comparable plasma VPA concentrations at the time of tremor testing.
  
  
  CONCLUSIONS
  This is the first study to assess quantitatively VPA-induced tremor by standardized tremor analysis. These results suggest that CR-VPA may cause less tremorigenic activity as compared with standard VPA. The mechanisms underlying this difference are unclear but may include greater peak-trough variation with VPA than with CR-VPA.
authors.affiliation: Department of Neurology, Innsbruck Medical University, Austria.
authors.forename: Martina
authors.initials: M
authors.lastname: Rinnerthaler
authors.forename: Gerhard
authors.initials: G
authors.lastname: Luef
authors.forename: Joerg
authors.initials: J
authors.lastname: Mueller
authors.forename: Klaus
authors.initials: K
authors.lastname: Seppi
authors.forename: Joerg
authors.initials: J
authors.lastname: Wissel
authors.forename: Eugen
authors.initials: E
authors.lastname: Trinka
authors.forename: Gerhard
authors.initials: G
authors.lastname: Bauer
authors.forename: Werner
authors.initials: W
authors.lastname: Poewe
mesh_terms: D000203:Activities of Daily Living / Q000145:classification; D000293:Adolescent; D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000008:administration & dosage* / Q000009:adverse effects*; D003692:Delayed-Action Preparations; D003936:Diagnosis, Computer-Assisted; D004185:Disability Evaluation; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012720:Severity of Illness Index; D014202:Tremor / Q000139:chemically induced* / Q000175:diagnosis*; D014635:Valproic Acid / Q000008:administration & dosage* / Q000009:adverse effects*
chemical_list: D000927:Anticonvulsants; D003692:Delayed-Action Preparations; D014635:Valproic Acid