Lanthanum Carbonate (Fosrenol®) to Reduce Oxalate Excretion in Patients With Secondary Hyperoxaluria and Nephrolithiasis

This study investigates the efficacy and the safety of Lanthanum Carbonate for the reduction of urinary oxalate excretion in patients with secondary hyperoxaluria and nephrolithiasis.

Inclusion Criteria: * able to give written informed consenct * hyperoxaluria (defined as urinary oxalate \> 45 mg/24 hours), demonstrated on 24-hour urine collection within 18 months prior to baseline visit * history of nephrolithiasis eGFR \> 60 mL/min/1.73m² (CKD-EPI formula) Exclusion Criteria: * primary hyperoxaluria, diagnosed by genetic testing * known allergy to Lanthanum Carbonate * hypophosphatemia (defined as serum phosphorus \< 0.81 mmol/L) * severe known liver insufficiency of biliary obstruction * rectocolitis ulcerohaemorraghica, Crohn's disease, bowel obstruction, stomach/duodenal ulceration * glucose/galactose malabsorption * severe diarrhea or other gastrointestinal disorder, which might interfere with the ability to absorb oral medication * pregnancy or breast-feeding * female participant of childbearing potential unwilling to take efficient contraceptive measures for the duration of the study * female participant without negative serum or urine pregnancy test * psychological illness or condition, interfering with the patient's compliance or ability to understand the requirements of the study * currently participating in another clinical trial