ALUMINUM HYDROXIDE, CALCIUM-CARBONATE AND CALCIUM ACETATE IN CHRONIC INTERMITTENT HEMODIALYSIS-PATIENTS

Background and methods: Prevention of secondary hyperparathyroidism in uremia necessitates correction of hyperphosphatemia and hypocalcemia. In order to avoid aluminum toxicity, calcium containing phosphate bin ders are used increasingly, instead of aluminium hydroxide. Recent stu dies have shown that calcium acetate has many characteristics of an id eal phosphate binder. It is, for instance, a more readily soluble salt compared with calcium carbonate. This advantage might, however, disap pear if calcium carbonate is taken on an empty stomach, a few minutes before meals. We examined the efficacy of three different phosphate bi nding agents in a randomized prospective study of 53 patients on regul ar hemodialysis. Bicarbonate dialyses were performed with a dialysate calcium concentration of 1.75 mmol/l. After a three-week wash-out peri od, patients received either aluminum hydroxide (control group), calci um acetate, or calcium carbonate as their phosphate binder. Patients w ere instructed to take the calcium salts a few minutes before meals on an empty stomach, and aluminum hydroxide during meals. Serum calcium, phosphate, intact parathormone, and alkaline phosphatase levels were determined every month. Patient compliance was estimated every month b y asking the patients which phosphate binder and what daily dose they had used. Results: Aluminum hydroxide tended to be the most effective phosphate binder. The mean +/- SEM required daily dose of calcium acet ate at 12 months was 5.04 +/- 0.60 g, corresponding to 10.1 +/- 1.20 t ablets of 500 mg. Co-medication with aluminum hydroxide, however, was needed (1.29 +/- 0.54 g per day, corresponding to 2.6 +/- 1.08 tablets of 500 mg). The required daily calcium carbonate dose appeared to be 2.71 +/- 0.48 g, corresponding to 5.4 +/- 0.95 capsules of 500 mg, wit h an adjuvant daily aluminum hydroxide dose of 0.69 +/- 0.27 g, corres ponding to 1.4 +/- 0.55 tablets of 500 mg (p = 0.0055). Thus, the mean daily doses of elemental calcium were comparable between the calcium acetate and calcium carbonate-treated patients (1.28 +/- 0.15 g versus 1.09 +/- 0.19 g; n.s.). The incidence of hypercalcemic episodes (albu min-corrected serum calcium levels above 2.80 mmol/l) in the calcium a cetate-treated group was 18% versus 31% in the calcium carbonate-treat ed group (p <0.005). None of the aluminum hydroxide-treated patients e xperienced hypercalcemic episodes. Mean serum concentrations of alkali ne phosphatase, intact parathormone, and aluminum did not differ betwe en the groups. Conclusions: In chronic intermittent hemodialysis patie nts, per gram administered elemental calcium phosphate binding with ei ther calcium acetate or calcium carbonate is equivalent, provided that calcium carbonate is taken on an empty stomach a few minutes before m eals. The number of capsules calcium carbonate, but also the total amo unt in grams, necessary to keep serum phosphate and intact parathormon e levels into an acceptable range then is significantly less. This mig ht improve patient compliance.