OBJECTIVES: To determine the real-world dose equivalency of sevelamer hydrochloride/carbonate (SH/C) and lanthanum carbonate (LC) monotherapies, and compare the drug costs associated with various dosages of SH/C versus conversion to LC. METHODS: Data were evaluated retrospectively for patients receiving hemodialysis in the US, who converted in either direction between SH/C and LC monotherapies, yet had similar phosphate (P) levels over the observation period. The study comprised a 90-day pre-conversion period followed by a 90-day post-conversion period. Serum P and daily P binder doses were assessed across six 30-day periods. Primary comparisons were based on data from the last month of each treatment period to allow for clinical equilibration. Drug cost assessments were based on prescription fills and REDBOOK pricing (Sept 2013). RESULTS: A total of 303 patients met study criteria: 128 converted from SH/C (mean dose ~8200 mg/day) to LC (~3400 mg/day) and 175 converted from LC (~3800 mg/day) to SH/C (~8600 mg/day). In the post-conversion, serum P ranged from 5.99±1.64 mg/dL to 6.43±1.87 mg/dL in patients converting from SH/C to LC, and from 6.18±1.68 mg/dL to 6.51±1.92 mg/dL in those converting from LC to SH/C. For combined patient cohorts, the overall dose equivalency of SH/C:LC was 2.27. Mean P binder costs were $1080±491/patient/month with SH/C and $1006±513 with LC. Mean cost differences between pre- and post-conversion phases, in either direction, were –$74.20/patient/month (95%CI –141.80, –6.63; p<0.05) in favor of LC. Cost differences between LC and SH/C were greatest (–$359; 95%CI –485, –260; p<0.001) in favor of LC, in patients receiving >7200 mg SH/C daily (50.7% of patients). CONCLUSIONS: Patients who converted between LC and SH/C monotherapies in either direction maintained similar P levels in both conversion phases. LC was 2.27 times as potent as SH/C on an mg-to-mg basis and was associated with significantly lower P binder costs.