Lithium Increases Platelet Count: [Letter]

Abstract

Some3, 4 but not all studies5, 6 have reported increased platelet counts: these, however, are limited by the brief (one to two weeks4, 5) or variable duration3 of lithium therapy, the use of comparison data from unmedicated controls rather than paired data,4 and the failure to compare directly the effect of lithium on platelets and white cells in the same patients.3 Therefore, we studied the effects of acute lithium treatment on white-cell and platelet counts in 21 patients (10 male and 11 female; mean age, 40.1±3 years [range, 26 to 571]) with primary affective disorders. Seventeen of the 21 subjects had increased platelet counts, and 16 subjects (12 of the 17 with increased platelet counts) had increased leukocyte counts after lithium treatment. [...]in five cases, the platelet count increased beyond the upper limit of the normal value of 364X103 per cubic millimeter (mean, 442±8.3X103 ; range, 389 to 489X103 ). Four patients, not included in our study sample, continued to have high platelet counts (range, 490 to 1026X 103 per cubic millimeter) after discontinuation of lithium treatment at the time of admission, and these counts persisted for two to four months while the subjects received no medication.