title: Effect of topiramate on plasma concentrations of clozapine, olanzapine, risperidone, and quetiapine in patients with psychotic disorders.
abstract: OBJECTIVE
  To investigate the effect of topiramate on the steady-state plasma concentrations of the second-generation antipsychotics--clozapine, olanzapine, risperidone, and quetiapine--in patients with schizophrenia or bipolar disorder.
  
  
  METHODS
  Thirty-eight outpatients on long-term treatment with clozapine (250-500 mg/d, n = 10), olanzapine (10-20 mg/d, n = 12), risperidone (3-6 mg/d, n = 9), or quetiapine (200-600 mg/d, n = 7) received adjunctive topiramate, gradually titrated up to a final dosage of 200 mg/d for 6 weeks. Pharmacokinetic assessments were made at baseline and at the end of treatment weeks 4 and 8 at topiramate dosages of 100 and 200 mg/d, respectively.
  
  
  RESULTS
  Plasma concentrations of clozapine and its metabolite (norclozapine), olanzapine, risperidone and its metabolite (9-hydroxy-risperidone), and quetiapine were not significantly modified during concomitant administration of topiramate. Adjunctive topiramate therapy was well tolerated in all groups.
  
  
  CONCLUSIONS
  These findings indicate that topiramate, at the dosages recommended for use as a mood stabilizer, does not affect the plasma levels of the new antipsychotics-clozapine, olanzapine, risperidone, and quetiapine.
authors.affiliation: Section of Pharmacology, Department of Clinical and Experimental Medicine and Pharmacology, University of Messina, Messina, Italy.
authors.forename: Gaetana
authors.initials: G
authors.lastname: Migliardi
authors.forename: Concetta
authors.initials: C
authors.lastname: D'Arrigo
authors.forename: Vincenza
authors.initials: V
authors.lastname: Santoro
authors.forename: Antonio
authors.initials: A
authors.lastname: Bruno
authors.forename: Lara
authors.initials: L
authors.lastname: Cortese
authors.forename: Domenica
authors.initials: D
authors.lastname: Campolo
authors.forename: Massimo
authors.initials: M
authors.lastname: Cacciola
authors.forename: Edoardo
authors.initials: E
authors.lastname: Spina
mesh_terms: D000328:Adult; D014150:Antipsychotic Agents / Q000097:blood* / Q000627:therapeutic use; D001569:Benzodiazepines / Q000097:blood / Q000627:therapeutic use; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003024:Clozapine / Q000097:blood / Q000627:therapeutic use; D003987:Dibenzothiazepines / Q000097:blood / Q000627:therapeutic use; D005260:Female; D005632:Fructose / Q000008:administration & dosage / Q000031:analogs & derivatives*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018696:Neuroprotective Agents / Q000008:administration & dosage*; D000077152:Olanzapine; D011618:Psychotic Disorders / Q000097:blood* / Q000188:drug therapy*; D000069348:Quetiapine Fumarate; D018967:Risperidone / Q000097:blood / Q000627:therapeutic use; D013997:Time Factors; D000077236:Topiramate
chemical_list: D014150:Antipsychotic Agents; D003987:Dibenzothiazepines; D018696:Neuroprotective Agents; D000077236:Topiramate; D001569:Benzodiazepines; D000069348:Quetiapine Fumarate; D005632:Fructose; D003024:Clozapine; D018967:Risperidone; D000077152:Olanzapine