title: Combined treatment of quetiapine with haloperidol in animal models of antipsychotic effect and extrapyramidal side effects: comparison with risperidone and chlorpromazine.
abstract: BACKGROUND
  Quetiapine, an atypical neuroleptic, has beneficial antipsychotic effects in schizophrenic patients, but with a lower incidence of extrapyramidal symptoms (EPS) compared with typical antipsychotics. While typical antipsychotics are often switched to atypical agents when adverse effects become limiting, there is little preclinical information to support this strategy, both in terms of efficacy and side effects.
  
  
  OBJECTIVE
  The antipsychotic effects and EPS during concomitant administration of quetiapine with haloperidol, a typical antipsychotic agent, were evaluated in mice and compared with chlorpromazine and risperidone.
  
  
  METHODS
  We first investigated the antipsychotic effects and EPS liability of quetiapine, risperidone, chlorpromazine, and haloperidol when administered alone to select optimal doses for subsequent combination studies. The second study was designed to evaluate the antipsychotic efficacy and EPS profile of concomitant administration of quetiapine, risperidone, or chlorpromazine with haloperidol. Antipsychotic effects were evaluated with the methamphetamine-induced hyperlocomotion test, and EPS liability was evaluated in a catalepsy-induction model.
  
  
  RESULTS
  Quetiapine, risperidone, chlorpromazine, and haloperidol dose-dependently reduced methamphetamine-induced hyperlocomotion, with ED50 values of 5.6, 0.020, 1.8, 0.035 mg/kg, respectively. In the catalepsy test, quetiapine only weakly induced catalepsy at the highest dose of 100 mg/kg, whereas risperidone, chlorpromazine, and haloperidol dose-dependently induced catalepsy with ED50 values of 0.25, 4.6, and 0.10 mg/kg, respectively. While the combination of quetiapine (6 mg/kg) and haloperidol (0.04 mg/kg) significantly reduced methamphetamine-induced hyperlocomotion in comparison with haloperidol alone, quetiapine (10, 32 mg/kg) plus haloperidol did not potentiate the cataleptogenic activity of haloperidol. In contrast, risperidone (0.1, 0.32 mg/kg) or chlorpromazine (3.2 mg/kg) significantly augmented catalepsy induced by haloperidol. Catalepsy induced by co-administration of quetiapine (10 mg/kg) and haloperidol (0.1 mg/kg) was significantly potentiated by WAY100635, a 5-HT1A antagonist, and catalepsy induced by co-administration of risperidone (0.1 mg/kg) and haloperidol (0.1 mg/kg) was significantly antagonized by 8-OH-DPAT, a 5-HT1A agonist.
  
  
  CONCLUSIONS
  The present study demonstrated that the combined administration of quetiapine with haloperidol did not aggravate EPS, possibly because of its affinity for 5-HT1A receptors. This finding may have the clinical implication that quetiapine could provide a successful regimen in switching from typical antipsychotic agents in the symptom management of schizophrenia, or even in adjunctive therapy with other antipsychotic agents.
authors.affiliation: Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co. Ltd, 2-1-6 Kashima, Yodogawa-ku, Osaka, 532-8514, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Tada
authors.forename: Kiyoharu
authors.initials: K
authors.lastname: Shirakawa
authors.forename: Nobuya
authors.initials: N
authors.lastname: Matsuoka
authors.forename: Seitaro
authors.initials: S
authors.lastname: Mutoh
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000008:administration & dosage / Q000493:pharmacokinetics; D000284:Administration, Oral; D000818:Animals; D014150:Antipsychotic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D001480:Basal Ganglia Diseases / Q000139:chemically induced* / Q000150:complications / Q000503:physiopathology; D002375:Catalepsy / Q000139:chemically induced / Q000188:drug therapy / Q000517:prevention & control; D002746:Chlorpromazine / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D003987:Dibenzothiazepines / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D006220:Haloperidol / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D006948:Hyperkinesis / Q000139:chemically induced / Q000517:prevention & control; D007274:Injections, Intraperitoneal; D008297:Male; D008694:Methamphetamine / Q000008:administration & dosage / Q000009:adverse effects / Q000037:antagonists & inhibitors; D051379:Mice; D010879:Piperazines / Q000008:administration & dosage / Q000493:pharmacokinetics; D011725:Pyridines / Q000008:administration & dosage / Q000493:pharmacokinetics; D000069348:Quetiapine Fumarate; D044282:Receptor, Serotonin, 5-HT1A / Q000008:administration & dosage; D018967:Risperidone / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D012559:Schizophrenia / Q000139:chemically induced / Q000150:complications / Q000188:drug therapy; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists
chemical_list: D014150:Antipsychotic Agents; D003987:Dibenzothiazepines; D010879:Piperazines; D011725:Pyridines; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists; D044282:Receptor, Serotonin, 5-HT1A; D000069348:Quetiapine Fumarate; D008694:Methamphetamine; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D006220:Haloperidol; D018967:Risperidone; D002746:Chlorpromazine