Long-term use of magnesium hydroxide as a phosphate binder in patients on hemodialysis

The long-term use of magnesium hydroxide [Mg(OH)2] as a phosphate binder was investigated in 18 patients on chronic hemodialysis. All patients received a basal treatment with oral calcium carbonate. Vitamin D supplements were not used. In period I each patient ingested aluminum hydroxide [Al(OH)3], in period II Mg(OH)2 and in period III Mg(OH)2 and Al(OH)3 together. During period II and III a dialysate devoid of Mg was used. Mg(OH)2 doses were adjusted to prevent severe hypermagnesemia and diarrhea. The mean dose of Mg(OH)2 in period II was 2.4 +/- 0.6 and in period III 2.6 +/- 1.2 g/day. Serum phosphate increased significantly in period II and fell again in period III. Despite a halving of the Al(OH)3 dose in period III, serum Al was similar in period I and period III (55.8 +/- 19.1 vs 57.1 +/- 27.3 microg/l). Parathyroid hormone (PTH) concentration fell in period II and decreased even further in period III. We conclude that oral Mg(OH)2 may reduce the required Al(OH)3 dose, however, without an effect on serum Al concentration. The observed suppression of parathyroid activity needs further study.