Haematological safety of antipsychotic drugs

Many clinicians have become concerned about the safety of new antipsychotics particularly in view of the association of agranulocytosis with clozapine and of aplastic anaemia with remoxipride. The Committee on Safety of Medicines and Medicines Control Agency 'yellow card' post-marketing surveillance data were analysed for reports of haemopoietic disorders with the 16 antipsychotics in common use. Corrections for relative risk were made in three separate ways: (i) control for degree of use, using Northern Ireland prescribing data for 1995; (ii) percentage of total reports from 1963 to 1996; and (iii) examination of the first 5 years' post-marketing data only. After clozapine and remoxipride the highest risks of haemopoietic reactions appeared to be associated with the aliphatic phenothiazine derivatives thioridazine and chlorpromazine. There is therefore no evidence of any increased risk with high-potency drugs such as haloperidol or pimozide or with the newer drugs such as sulpiride or risperidone. Continued vigilance, however, is necessary as more new atypicals become available and begin to be widely prescribed.