Risks with warfarin greater in renal disease

WARFARIN may need to be initiated at lower doses in patients with moderate to severe chronic kidney disease (CKD) in order to reduce their risk of haemorrhage.

A US study of 578 patients found those with severe CKD (eGFR of <30 ml/min per 1.73 kg/m²) had more than double the risk of major haemorrhage when taking warfarin than did those with mild or no kidney dysfunction.   

Patients with moderate CKD (eGFR 30-59 ml/min per 1.73 kg/m²) had a 30% increased risk of major haemorrhage. 

As 40% of those in the study had severe or moderate CKD, “these findings highlight that diminished renal function may have implications for a larger proportion of warfarin users than previously estimated,” the authors said.

They said CKD could “significantly reduce non-renal clearance and alter the bioavailability of drugs predominantly metabolised by the liver”.

Professor Alexander Gallus, professor of haematology at Flinders University school of medicine, Adelaide, said current Australasian Society of Thrombosis and Haemostasis warfarin management guidelines, last reviewed in 2000, should be updated to include “determinants” on the risk of bleeding and unstable anticoagulant effects in patients with severe CKD.

He said that, while the benefits of warfarin treatment in these patients outweighed the risks, the results highlighted their need for lower initial dosage and increased monitoring.

J Am Soc Nephrol, online 18 February.