A comparison of European and American dosing regimens of schizophrenic patients on clozapine: efficacy and side effects.

We present a comparison of the results from two studies of patients on clozapine. The American study (n = 84; Hillside Hospital, Glen Oaks, NY) and the European study (n = 63; Innsbruck University Clinics, Innsbruck, Austria) both examine efficacy and side effects in schizophrenic patients on this atypical neuroleptic. There is a very substantial difference in the dosing regimen used on both continents and this is reflected in the studies reported. A question with major clinical implications is whether the higher doses commonly used in the United States lead to a better outcome or a different profile of side effects. Outcome as a function of serum concentration will be examined. Results confirm a lower dose, lower clozapine blood level, and a lesser degree of side effects in the Austrian cohort when compared to the American sample. Surprisingly, the clinical efficacy of the lower dosing regimen was superior to the higher dose. Reasons for this anomaly are explored.