Active monitoring of 12,760 clozapine recipients in the UK and Ireland. Beyond pharmacovigilance.

BACKGROUND

People prescribed clozapine for treatment-resistant schizophrenia have mandatory haematological monitoring through a case register for identifying reversible neutropenia.

AIMS: To quantify risk factors for agranulocytosis in subjects receiving clozapine.

METHOD: Data from 12,760 subjects registered to receive clozapine from January 1990 to April 1997 were analysed. Risk factors for agranulocytosis were quantified using a Cox proportional-hazards regression analysis.

RESULTS

The risk for agranulocytosis in Asian subjects was 2.4 times that in Caucasians (P = 0.03). There was an age-related increase in risk of 53% per decade (P = 0.0001).

CONCLUSIONS

The case register yielded valuable information for guiding research into the causes of the haematological reactions.