Granulocyte colony-stimulating factor plasma levels during clozapine- and olanzapine-induced granulocytopenia

Recent case studies suggest that impaired granulopoiesis, well-known to occur during clozapine treatment, may also be observed when olanzapine is administered. The underlying mechanisms are unknown, but haematopoietic cytokines such as granulocyte colony-stimulating factor (G-CSF) are likely to be involved.

We measured the plasma levels of G-CSF and of other cytokines longitudinally in a female patient who developed granulocytopenia twice, first during clozapine treatment and again when olanzapine was administered.

G-CSF levels, but not those of other cytokines, closely paralleled granulocyte counts, yielding a significant positive correlation. G-CSF was not detectable in plasma when granulocytopenia occurred. Granulocytopenia resolved spontaneously despite continuing treatment with olanzapine.

The present case suggests that clozapine and olanzapine both are able to induce transient granulocytopenia through a similar or common mechanism that does not involve a compensatory increase in G-CSF levels.