Effect of famotidine and lansoprazole on serum phosphorus levels in hemodialysis patients on calcium carbonate therapy.

AIMS: Histamine H2 receptor antagonists (HRA) or proton pump inhibitors (PPI) are frequently administered to patients on hemodialysis, because their intestinal mucosa is fragile. Although three studies have indicated that concomitant HRA administration causes a decrease in the binding of phosphate by calcium carbonate, the HRA doses tested in these studies were 2-4 times higher than the recommended dose for hemodialysis patients. In addition, it remains unclear whether PPI therapy affects serum phosphate levels in hemodialysis patients taking calcium carbonate. Accordingly, the aim of this study was to evaluate the influence of lansoprazole and the recommended dose of famotidine on serum phosphate and calcium levels in hemodialysis patients.

METHODS: The study included 115 hemodialysis patients who were taking calcium carbonate and who were also treated with either famotidine (10 mg/day) or lansoprazole (30 mg/day). Changes of the mean serum phosphate and calcium levels over 2 months before and after the start of famotidine or lansoprazole therapy were compared. The same parameters were also compared when famotidine was switched to lansoprazole.

RESULTS: The mean serum phosphate level increased significantly after administration of either famotidine or lansoprazole (by 6.6 +/- 21.9% or 13.0 +/- 26.3%, p = 0.032 and p = 0.029, respectively). The mean serum calcium level was unchanged after administration of famotidine, but showed a significant decrease after administration of lansoprazole (by 3.44 +/- 7.73%, p = 0.013). Therefore, the calcium x phosphorus product was significantly increased by administration of famotidine, but not by administration of lansoprazole (6.68 +/- 23.37% and 8.73 +/- 27.41%, p = 0.046 and p = 0.251, respectively). When famotidine was switched to lansoprazole, the serum phosophate level did not change, but serum calcium decreased significantly by 3.8 +/- 13.0% (p = 0.0006).

CONCLUSION: Not only administration of 20 mg/ day of famotidine as previously reported, but also 10 mg/day of this drug (the recommended dose for hemodialysis patients) caused a significant increase of serum phosphate in patients taking calcium carbonate. PPIs have been reported to show no effect on the serum phosphate level, but 30 mg/day of lansoprazole also caused a significant increase of serum phosphate in patients taking calcium carbonate.