Losartan, an angiotensin-II receptor antagonist, reduces hematocrits in kidney transplant recipients with posttransplant erythrocytosis.
BACKGROUND
Posttransplant erythrocytosis (PTE) occurs in 10-15% of patients with a well-functioning kidney transplant and is associated with increased morbidity. Although the mechanism of PTE is unknown, PTE responds to inhibitors of ACE (ACE-i) in most cases. ACE converts angiotensin I to angiotensin II and is a metabolizer of a number of other peptides.


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with newly diagnosed PTE, two with PTE unresponsive to ACE-i, and one with PTE responsive to ACE-i, which had to be withdrawn due to side effects) with 50 mg of the type 1 angiotensin II receptor antagonist losartan for at least 14 weeks.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 decreased 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, paired 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 patients.


CONCLUSIONS
We conclude that blockade of the type 1 angiotensin II receptor is safe and effective in treating PTE.
Klaassen
R J
RJ
Department of Nephrology, University Hospital Rotterdam Dijkzigt, the Netherlands.
van Gelder
T
T
Rischen-Vos
J
J
Deinum
J
J
Man in't Veld
A J
AJ
Weimar
W
W
D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds / Q000494:pharmacology*; D004906:Erythrocyte Count / Q000187:drug effects; D006400:Hematocrit; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D016030:Kidney Transplantation / Q000009:adverse effects*; D019808:Losartan; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011086:Polycythemia / Q000097:blood / Q000209:etiology*; D013777:Tetrazoles / Q000494:pharmacology*
D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D007093:Imidazoles; D010975:Platelet Aggregation Inhibitors; D013777:Tetrazoles; D019808:Losartan