A combination of aspirin and the antiplatelet drug dipyridamole can significantly decrease the risk of patency loss in new arteriovenous (AV) hemodialysis (HD) grafts, according to a five-year study.

“Our trial results show that we now have a drug therapy which significantly prolongs the viability of AV grafts,” said lead investigator Bradley S. Dixon, MD, Associate Professor of Medicine at the University of Iowa College of Medicine in Iowa City. “This is an important step forward as we proceed to develop therapies to improve dialysis patients’ quality of life.”

“This drug combination provides a modest but important new therapy to keep AV grafts in good working order so patients can get the dialysis they need,” said Griffin P. Rodgers, MD, Director of the National Institute of Diabetes and Digestive and Kidney Diseases, which supported the trial.

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“But clearly more research is needed to extend the useful life of AV grafts.” Study findings appear in The New England Journal of Medicine (2009;360:2191-2201).

Conducted at 13 clinical sites in the United States, the study involved 649 HD patients who recently received an AV graft. Subjects were randomly assigned to receive dipyridamole 200 mg plus aspirin 25 mg twice daily (321 patients) or a placebo (328 patients) over 4.5 years, with six additional months of follow-up.

The median duration of patency was 5.8 months in the combined-treatment arm compared with 4.3 months in the placebo group. The combination treatment decreased the risk of primary unassisted graft patency loss by 18% and the rate of significant stenosis (50% or greater) by 28% compared with placebo, after adjusting for serum albumin level and use or nonuse of ACE inhibitors or angiotensin receptor blockers.

The rate of cumulative graft failure was 50% in the combination-treatment arm and 53% in the placebo recipients, a nonsignificant difference between the groups. The incidence of serious adverse events, including bleeding, also did not differ between the study arms.

With respect to study limitations, the authors noted that they did not meet their enrollment goal, which could limit the applicability of the subgroup analyses.

In addition, study drugs were stopped after the primary outcome (loss of primary unassisted patency) was reached, so “the possible benefit of continued treatment with dipyridamole plus aspirin on cumulative graft patency could not be evaluated.”