Newer vitamin D raises chances of dialysis survival

Dialysis patients taking a particular intravenous vitamin D formulation have a significant survival advantage over patients taking an older and more commonly used form of vitamin D, according to a study published in the 31 July edition of the New England Journal of Medicine​.

The three-year study found that patients receiving paricalcitol had a 16 per cent greater chance of survival than did patients receiving calcitriol.

"This is the first evidence that a specific form of vitamin D can change the high rate of mortality among dialysis patients,"​ said Dr Ravi Thadhani of the Massachusetts General Hospital's Renal Unit, the paper's senior author. "If further research confirms our findings, this will be very important information for dialysis patients and their physicians."​

Cardiovascular disease is the primary cause of death among dialysis patients, and recently attention has been paid to the impact of hyperparathyroidism - overactivity of the parathyroid gland - on vascular disease.

Paricalcitol is a vitamin D analog that was approved by the US Food and Drug Administration in 1998 to treat hyperparathyroidism associated with kidney failure. Because paricalcitol was known to be associated with more stable blood calcium and phosphorous levels and was effective in patients with high phosphorous levels, who tend to be resistant to the standard calcitriol, Thadhani and his colleagues decided to analyze whether the newer medication had an impact on patient survival.

The research team followed 67,000 hemodialysis patients who started receiving intravenous vitamin D treatment on or after 1 January 1999. Of these patients, 29,000 started with paricalcitol and 38,000 received calcitriol. During the three-year study, 16,000 patients switched from one vitamin D formulation to another. All treatment decisions were made by the treating physicians, rather than the research team.

At the end of the study period, the researchers noted a 16 per cent better survival among patients taking paricalcitol. Higher survival rates with paricalcitol were also noted among African American patients and diabetic patients -groups that have higher mortality rates on dialysis than the average. In addition, patients who switched from calcitriol to paricalcitol seemed to live longer than did those that made the reverse switch.

"This is the first study to look at the impact on survival of different types of vitamin D, an important nutrient necessary for normal function,"​ Thadhani said. But the team still need to investigate the mechanism behind this improved survival. "That could give us more knowledge about how vitamin D is really working and how we might apply these findings to patients before they start dialysis, as well as those who undergo a kidney transplant,"​ added Thadhani.

Thadhani and his colleagues noted that a randomised, controlled clinical trial of paricalcitol versus calcitriol is required before firm conclusions are made.