Improving outcomes in hyperphosphataemia.
Preclinical studies have shown that lanthanum has a very high phosphate-binding capacity at gastrointestinal pH, while clinical trials have shown lanthanum carbonate to be an effective, well-tolerated phosphate binder for the treatment of hyperphosphataemia in patients with end-stage renal disease. Optimization of bone health is an important issue in these patients, and, based on theoretical grounds, there have been concerns that lanthanum will have toxic effects on bone similar to those of aluminium. However, compared with aluminium, absorption of lanthanum is extremely low and lanthanum treatment is not associated with systemic toxicity. In addition, unlike aluminium, elimination of lanthanum is not through the kidney, but mainly takes place via the biliary route and is, therefore, independent of renal function. This implies that patients with chronic renal failure are not at an increased risk for accumulation of the element, compared with patients with normal renal function. In animal studies, no adverse effects on bone were seen in healthy animals receiving lanthanum carbonate. In 5/6th nephrectomized rats, very high doses of lanthanum (1000-2000 mg/kg) affected bone mineralization. This was not due to a direct toxic effect on bone, but was secondary to phosphate depletion induced by lanthanum and, as with any gastro-intestinal phosphate-binding agent, can be reversed with a phosphate-supplemented diet. In a phase III clinical trial, bone biopsies were taken from dialysis patients at baseline and after 1 year of treatment with either lanthanum carbonate (median dose, 1250 mg/day) or calcium carbonate (median dose, 2000 mg/day). Patients treated with lanthanum carbonate for 1 year did not experience any of the aluminium-like toxic effects on bone expressed as either osteomalacia or adynamic bone disease.