LOSARTAN, AN ANGIOTENSIN-II RECEPTOR ANTAGONIST REDUCES HEMATOCRITS IN KIDNEY-TRANSPLANT RECIPIENTS WITH POSTTRANSPLANT ERYTHROCYTOSIS

Background. Posttransplant erythrocytosis (PTE) occurs in 10-15% of pa tients with a well-functioning kidney transplant and is associated wit h increased morbidity. Although the mechanism of PTE is unknown, PTE r esponds to inhibitors of ACE (ACE-i) in most cases. ACE converts angio tensin I to angiotensin II and is a metabolizer of a number of other p eptides. Methods. Because ACE-i frequently show side effects we wanted to elucidate the pathway by which ACE-i mediate their effect in PTE. Therefore, we treated eight patients (five with newly diagnosed PTE, t wo with PTE unresponsive to ACE-i, and one with PTE responsive to ACE- i, which had to be withdrawn due to side effects) with 50 mg of the ty pe 1 angiotensin II receptor antagonist losartan for at least 14 weeks . Results. Hematocrit values in the two patients who were unresponsive to ACE-i did not change significantly. In contrast, hematocrits decre ased in all the other six patients from 0.53 +/- 0.02 to 0.44 +/- 0.02 after 14 weeks of treatment with losartan (mean +/- SE; P<0.005, pair ed t test). Graft function, cyclosporine concentration, and leukocyte and platelet count remained stable. The serum potassium level rose in one patient from 6.0 to 6.8 mmol/L but remained stable in all other pa tients. Conclusions. We conclude that blockade of the type 1 angiotens in II receptor is safe and effective in treating PTE.