Dose dependent suppression of mineralocorticoid metabolism by different heparin fractions.

One neglected side effect of heparin therapy is the inhibition of adrenal aldosterone production leading to occasionally life-threatening hyperkalaemia. This is only reported with (therapeutic) high doses (greater than or equal to 20.000 IU). The complex interplay of mineralocorticoid metabolites was studied in 29 subjects with unfractionated (UFH) and low molecular weight heparin (LMWH). Both heparins altered mineralocorticoid metabolism in a dose dependent manner. Whereas no effect was observed with UFH 2 x 5000 IU sc/day or LMWH 2500 a FXa U sc/day, higher doses significantly suppressed aldosterone and 18-hydroxycorticosterone production in plasma and urine. Three out of seven patients receiving UFH 3 x 7500 IU sc/day developed hyperkalaemia. This study shows the threshold dosage of UFH leading to suppression of mineralocorticoid metabolism in man and provides information that LMWH as well as UFH can suppress mineralocorticoid production. With respect to therapeutic implications it is important that LMWH at 2500 a FXa U sc/d had no effect on mineralocorticoid metabolism in contrast to UFH at a dosage currently used for prevention of thromboembolism (3 x 5000 IU sc/d).