United Kingdom. Therapeutic doses of both unfractionated and low molecular weight heparins can inhibit the secretion of aldosterone, causing an increase in plasma potassium which may be clinically significant. Certain types of patients seem to be more susceptible to the suppression of aldosterone secretion, such as those with diabetes mellitus, chronic renal failure, pre-existing acidosis, raised plasma potassium, or those taking potassium sparing drugs. The risk appears to increase with the duration of therapy. Plasma potassium should be measured in patients at risk before starting heparin and monitored regularly thereafter, particularly if heparin is continued for more than 7 days.

The product information for heparin is being updated to reflect this new advice.

[See also Pharmaceuticals Newsletter No.1, January 1991]

References:

1) Current Problems in Pharmacovigilance Vol. 25, March 1999.

2) Oster JR, Singer I, & Fishman LM. Heparin-induced aldosterone suppression and hyperkalemia. American Journal of Medicine 98: 575-586 (1995).

3) Monreal M, Lafoz E, Salvador R et al. Adverse effects of three different forms of heparin therapy: thrombocytopenia, increased transaminases, and hyperkalaemia. European Journal of Clinical Pharmacology 37: 415-418 (1989).