Lithium dosage and leukocyte counts in psychiatric patients.

OBJECTIVE

To evaluate differences in leukocyte counts among patients treated with either lithium alone, antipsychotic medications alone, or a combination of both.

DESIGN

Retrospective study.

SETTING

Long-stay psychiatric hospital.

PATIENTS

Patients admitted between 1990 and 1993, and treated with lithium for at least 1 week and/or with antipsychotic medication for at least 2 weeks. Excluded from the study were those patients for whom complete blood counts at baseline and during therapy were not available, and those patients whose blood picture could primarily be accounted for by extraneous factors. Included in the study were 38 patients treated with lithium alone, 207 patients receiving antipsychotic medications alone, and 71 patients receiving both.

OUTCOME MEASURES

Leukocyte, lymphocyte and granulocyte counts.

RESULTS

Patients treated with lithium alone had significantly higher mean leukocyte and granulocyte counts than those treated with antipsychotic medication alone (analysis of variance, p < 0.05). None of the patients receiving lithium alone showed leukopenia. The dosage of lithium was significantly correlated with leukocyte count (r = 0.25, 95% confidence interval [CI] 0.14 to 0.35, p < 0.001,) and granulocyte count (r = 0.27, 95% CI 0.16 to 0.38, p < 0.001), but not with lymphocyte count (r = 0.06, p = 0.286, 95% CI -0.05 to 0.17).

CONCLUSIONS

Lithium therapy is associated with higher leukocyte and granulocyte levels in psychiatric patients. This leukocytotic effect of lithium may be dose dependent.