A comparison of the effects of quetiapine ('Seroquel') and haloperidol in schizophrenic patients with a history of and a demonstrated, partial response to conventional antipsychotic treatment

Quetiapine ('Seroquel') is a well-tolerated, novel, atypical antipsychotic with consistent efficacy in the treatment of schizophrenia. To date, no cli nical studies have evaluated the effect of quetiapine in patients who only partially respond to conventional antipsychotics, yet this type of patient is most frequently seen by psychiatrists. Therefore, this international, mu lticentre, double-blind study was conducted to compare the efficacy and tol erability of 8 weeks' treatment of quetiapine 600 mg/day with haloperidol 2 0 mg/day in 288 patients who had a history of partial response to conventio nal antipsychotics and displayed a partial or no response to 1 month of flu phenazine (20 mg/day) treatment. Patients on quetiapine tended to have grea ter improvement than those on haloperidol in the primary efficacy measure, mean Positive and Negative Symptom Scale (PANSS) score, after 4 weeks' trea tment (-9.05, -5.82, respectively, P = 0.061) and at study end (-11.50, -8. 87, respectively, P = 0.234). Similarly, there was a trend towards patients on quetiapine demonstrating greater improvements in the secondary efficacy measures (Clinical Global Impression, PANSS subscale and Brief Psychiatric Rating Scale scores) [week 4 (baseline) to week 12 (end)], but the differe nce between treatments did not reach significance. Significantly more patie nts on quetiapine than on haloperidol showed a clinical response - patient response rates, defined as greater than or equal to 20% reduction in PANSS total score between weeks 4 and 12, were 52.2% for quetiapine and 38.0% for haloperidol (P = 0.043). Patients receiving quetiapine required less antic holinergic medication (P less than or equal to 0.011), had greater reductio n in extrapyramidal symptoms (EPS) (P = 0.005) and fewer treatment-emergent EPS-related adverse events compared to those on haloperidol (P < 0.001). S erum prolactin concentrations were elevated at the end of fluphenazine trea tment in 73% of patients. Between weeks 4 and 12, elevated serum prolactin concentrations significantly decreased in quetiapine-treated patients compa red to those receiving haloperidol (P < 0.001). At the end of quetiapine tr eatment, 83% of patients had normal prolactin levels while only 21% of pati ents receiving haloperidol were within the normal range. These results sugg est that quetiapine may make a valuable contribution to the management of p atients with a history of partial response to conventional antipsychotics. (C) 2000 Lippincott Williams & Wilkins.