Correction of metabolic acidosis after conversion from sevelamer hydrochloride to lanthanum carbonate

Sir,We recently introduced lanthanum carbonate as an alter-native phosphate binder to sevelamer hydrochloride in pa-tients with elevated serum calcium. Lanthanum carbonatehas a higher affinity for phosphate than sevelamer HCl, sofewer lanthanum carbonate tablets are required to achievethe same phosphate control. To reduce the pill burden inpatients on high doses of sevelamer HCl, a policy of con-verting patients who were prescribed 8–12 sevelamer perday, and patients currently on 6 sevelamer per day but inneed of a dose increase, to 3 × 750 mg lanthanum car-bonate per day was established. Conversions were made atthe discretion of the doctor, so that well-controlled patientswere less likely to switch.In October 2007, 60 haemodialysis patients convertedaccording to the above criteria. Of these, 13 patients whodislikedorwereintolerantoflanthanumcarbonaterevertedto sevelamer HCl within 3 months. Forty-seven patients(68% male, median age 47 years, range 21–79) continuedto take lanthanum carbonate.Several studies have suggested that sevelamer HCl con-tributes to metabolic acidosis [1,2], while lanthanum car-bonate would be expected to have an antacid effect. Acomparison of the median of three routine (monthly) pre-dialysis serum bicarbonate and phosphate measurementsimmediately before and after conversion for each patientshowed an increase in serum bicarbonate from a meanof 20.3 ± 2.3 to 22.2 ± 2.4 mmol/l (