Calcium Acetate

When phosphate keeps running high

Dairy, meat, nuts, cola and whole grains all bring phosphate into the body, and healthy kidneys clear the surplus from the blood. When the kidneys fail, especially in people on dialysis, phosphate builds up between sessions, and trimming the diet only goes part of the way. Over the years that build-up is linked to weaker bones and calcium deposits in blood vessels. Binders such as calcium acetate are taken with meals to help the diet and dialysis do their job.

How the tablets work

Calcium acetate acts inside the gut rather than in the blood. Swallowed with food, it reacts with the phosphate released as the meal is digested and forms calcium phosphate, a compound the bowel cannot absorb; the phosphate leaves the body in stool instead of reaching the bloodstream. The reaction needs food present, so timing carries more weight than the total daily amount: tablets go with each meal, and the count differs from meal to meal — often more with a main meal, fewer with breakfast or a snack — adjusted as blood results change.

Phoslo 667mg tablets

Phoslo is the calcium acetate product sold on PockDose, a 667mg tablet. Its use is hyperphosphataemia (too much phosphate in the blood) in chronic kidney failure. It sits in the bone support group because long-term phosphate control is largely about protecting bone. The 667mg figure is the weight of the whole calcium acetate molecule, not of calcium alone: a large share of it is the acetate part, and the calcium within the molecule is what latches onto phosphate from a meal.

Side effects

Stomach upset is the usual complaint — nausea, a heavy feeling, constipation or looser stools, sometimes vomiting — most often when treatment starts or the dose goes up. The concern with any calcium-based binder is calcium creeping too high in the blood (hypercalcaemia). Unusual tiredness, confusion, thirst, passing more urine than usual, muscle weakness or nausea that will not settle can all point to that. Routine dialysis blood tests track calcium and phosphate together, and the tablet count is changed when calcium drifts up.

Other medicines, and keeping the tablets

Calcium acetate can reduce the absorption of some medicines taken at the same time — tetracycline and quinolone antibiotics, iron tablets, levothyroxine and others — so those are spaced to a different point in the day. Store the tablets somewhere dry and out of direct sun, in their packaging, and use them before the date on the pack.