title: Retention rate of zonisamide in intractable epilepsy.
abstract: OBJECTIVE
  To assess the effect and tolerability of zonisamide (ZNS) as adjunctive treatment for difficult-to-treat epilepsy in adult Scandinavian patients.
  
  
  METHODS
  151 outpatients (mean age: 42.5 years) from 18 centres in Denmark, Sweden and Norway were recruited to the study. 81.5% had focal epilepsy, and the mean number of previously tried AEDs was 4.5. The patients were given ZNS as add-on treatment, and the ZNS dosing and the visit frequency were governed by the treating physician. The primary efficacy endpoint was the retention rate after 12-month treatment. Assessments included also responder rate, type and frequency of adverse events, healthcare resource utilization (HCRU) and quality of life (QOLIE-31).
  
  
  RESULTS
  90 patients (59.6%) completed the study. Mean daily ZNS dose was 300.8 mg. After 12 months, 81 patients were still on ZNS, that is a retention rate of 53.6%. The mean reduction of seizure frequency at 12 months was 27%. Best effect was seen in those with focal and those with secondary generalized seizures. In the QOLIE-31, there was a mean increase from baseline of 4.8 points. The tolerability was generally good. The majority of side effects were CNS-related, dizziness, fatigue, seizure aggravation, and headache being most prevalent. 21.2% had adverse events leading to withdrawal of ZNS.
  
  
  CONCLUSIONS
  A retention rate of 53.6% after 1 year of treatment with ZNS is roughly in accordance with the retention rates found for lamotrigine, oxcarbazepine, levetiracetam and topiramate in drug-resistant patients.
authors: National Centre for Epilepsy, Sandvika, Norway.
authors: K O
authors: KO
authors: Nakken
authors: P
authors: P
authors: Lindstrøm
authors: H
authors: H
authors: Andersen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000008:administration & dosage* / Q000009:adverse effects; D003718:Denmark; D004359:Drug Therapy, Combination; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D006801:Humans; D007555:Isoxazoles / Q000008:administration & dosage* / Q000009:adverse effects; D000077213:Lamotrigine; D000077287:Levetiracetam; D008297:Male; D008875:Middle Aged; D009664:Norway; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D010889:Piracetam / Q000008:administration & dosage / Q000031:analogs & derivatives; D011788:Quality of Life; D013548:Sweden; D016896:Treatment Outcome; D014227:Triazines / Q000008:administration & dosage; D055815:Young Adult; D000078305:Zonisamide
chemical_list: D000927:Anticonvulsants; D007555:Isoxazoles; D014227:Triazines; D000077287:Levetiracetam; D000078305:Zonisamide; D000077213:Lamotrigine; D010889:Piracetam
keywords: adverse effects; antiepileptic drugs; epilepsy; seizures; treatment