Elevated platelet counts with lithium and neuroleptics.

Fråga: Elevated platelet counts with lithium and neuroleptics.

Sammanfattning: Increases in platelet levels have been reported to occur during lithium therapy, when administered alone. The clinical implications of the increased levels has not been well established. No similar effect has been observed or reported when lithium has been administered concomitantly with neuroleptic or other antidepressant agents in the few available studies.

Svar: Statistically significant increases in platelet counts compared to baseline levels have been reported during lithium therapy (1-3). The clinical significance has not been established as in one report (1), five of 17 subjects with increased level presented with counts beyond the upper limit of normal, while in another (2), all the increased platelet levels remained within the normal range. In some patients the increase in platelet counts persisted two to four months after lithium therapy was discontinued (1). The increase in platelets was not related to lithium blood levels (1,2), lithium dosage or length of lithium administration (2), nor was there a correlation between the elevated platelet counts and leukocytosis (1).

The mechanism for this effect of lithium therapy is not known, although it has been suggested that it may be due to stimulation of platelet precursors in the bone marrow or cells in the stem cell compartment to differentiate to precursors of thrombopoiesis (3). Experiments in mice have shown a stimulatory effect by lithium on megakaryocytopoiesis (4).

No elevation of platelet levels has been observed in patients receiving lithium concomitantly with neuroleptics or antidepressants (2).

No reports of elevated platelet counts associated with the use of neuroleptics have been found. However, the opposite effect, thrombocytopenia, is cited as a side effect of the use of phenothiazines (5,6).