In a new review published in Nutrition and Diabetes, researchers highlight the role of phosphate-containing medications and foods with a low phosphorus to protein ratio in reducing intestinal phosphorus load in patients with chronic kidney disease (CKD).

Many drugs commonly prescribed to CKD patients contain phosphorus. Studies show, however, that the amounts of phosphate in a specific drug varies by formulation and even manufacturer, Baihai Su, MD, of Sichuan University in China, and colleagues explained. For example, amlodipine 10 mg for a dialysis patient contains anywhere from 7.9 to 165.6 mg of available phosphorus, depending on the producer. More than 1 in 5 of medications in the following categories contain phosphate as an excipient:

  • Calcium channel blockers (51%)
  • Pain medicines (45%)
  • Antipsychotics (35%)
  • Vitamins (29%)
  • Diabetes drugs (24%)
  • Beta blockers (23%)
  • Cholesterol-lowering therapy (21%)

The team highlighted that both pharmaceutical excipients and food additives contain inorganic phosphates that are readily absorbed from the intestine.

“The estimated phosphorus load in medications in 90% of the patients with CKD may be <80 mg/day, which is much lower than the phosphorus load from food additives, which could be as high as 800 mg in certain patient populations,” Dr Su and collaborators wrote. “Nevertheless, medicinal drugs as a hidden source of phosphorus in patients with CKD cannot be neglected.”

The reviewers urged careful prescription of phosphate-containing medications and consideration of alternative drugs to reduce intestinal phosphorus load. First, they acknowledged, pharmaceutical companies must declare phosphorus amounts in products. They cited “a lack of transparency” in declaring the excipient phosphorus content.

Dr Su and colleaguesalso emphasized using the dietary phosphate (mg) to protein (g) ratio to select foods for a “healthy” CKD diet. The estimated phosphorus load from 1 g of protein is around 13 to 15 mg, of which 30%–70% is intestinally absorbed. Low phosphorus foods (eg, egg white) have a phosphorus–protein ratio of less than 12 mg/g.

Reference

Li J, Wang L, Han M, et al. The role of phosphate-containing medications and low dietary phosphorus/protein ratio in reducing intestinal phosphorus load in patients with chronic kidney disease. Nutr Diab 9:14. DOI:10.1038/s41387-019-0080-2