Abstract |
Clozapine, a novel antipsychotic drug that is particularly effective in treatment-resistant schizophrenia, causes severe agranulocytosis of unknown aetiology in approximately 0.8% of U.S. patients. We evaluated potential toxic mechanisms of drug-induced agranulocytosis. Clozapine, the two major metabolites N-desmethylclozapine and N- oxide clozapine, and five other clozapine derivatives were screened for toxicity to normal haemopoietic precursors. For all compounds except N-des-methylclozapine, toxicity to CFU-GM, BFU-E and CFU-GEMM occurred at concentrations at least 10 times the normal serum levels reported in unaffected patients. In contrast, the LD50 for N-desmethylclozapine was 2.5 micrograms/ml for CFU-GM, 3.2 micrograms/ml for BFU-E, and 2.4 micrograms/ml for CFU-GEMM, only 3-6 times the normal serum concentration. Bone marrow from patients with acute clozapine-induced agranulocytosis was not more sensitive to clozapine or N-desmethylclozapine than bone marrow from normal donors. These studies suggest that N-desmethylclozapine, the major metabolite of clozapine, is itself toxic or is further metabolized to an unstable compound which is toxic to haemopoietic precursors of both myeloid and erythroid lineages.
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Authors | S L Gerson, C Arce, H Y Meltzer |
Journal | British journal of haematology
(Br J Haematol)
Vol. 86
Issue 3
Pg. 555-61
(Mar 1994)
ISSN: 0007-1048 [Print] England |
PMID | 8043437
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
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Chemical References |
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Topics |
- Agranulocytosis
(blood, chemically induced)
- Cell Survival
(drug effects)
- Cells, Cultured
- Clozapine
(adverse effects, analogs & derivatives, chemistry, metabolism, pharmacology)
- Colony-Forming Units Assay
- Dose-Response Relationship, Drug
- Hematopoiesis
(drug effects)
- Hematopoietic Stem Cells
(drug effects)
- Humans
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