blood level monitoring reduces risk of agranulocytosis to 0.03%

The monitoring of blood levels seems to be effective in preventing mortality through agranulocytosis

http://bjp.rcpsych.org/cgi/content/abstract/169/4/483
Neutropenia and agranulocytosis in patients receiving clozapine in the UK and Ireland
Atkin, K. 1996

BACKGROUND: Clozapine can cause reversible agranulocytosis and neutropenia. This study documents the occurrence of blood dyscrasias and identifies predisposing risk factors. METHOD: An analysis was made of thehaematological, demographic, and dosage data from a central database on 6316 patients receiving clozapine over four and a half years in the UK and Ireland. RESULTS: During the study period, 2.9% of the patients developed neutropenia and 0.8% developed agranulocytosis. The peak incidence of both disorders was in the first 6-18 weeks of treatment. Fatal agranulocytosis occurred in 0.03% of patients. After the first year of treatment, the incidence of agranulocytosis significantly decreased to the order noted with some phenothiazines. CONCLUSIONS: The use of a patient monitoring service kept the haematological risks associated with using clozapine within acceptable limits, particularly in view of the benefits of this medication in treatment-resistant schizophrenia.