Impact of Potassium-Binders on the Interpretation of Bone Mineral Density Following Kidney Transplantation

Following kidney transplantation (KTx), episodes of hyperkalemia are common and effectively treated with sodium zirconium cyclosilicate (SZC, Lokelma) or patiromer (PAT, Veltassa). The presence of SZC/PAT in the gastrointestinal tract may, if radio dense, influence the interpretation of lumbar spine (LS) dual-energy x-ray absorptiometry (DXA)-scans. We investigated the effect with/without PAT/SZC in KTx on LS DXA readings.

A prospective, single-center study of KTx recipients in need of potassium-lowering therapy was performed. All participants performed two LS DXA-scans, the first after at least 3 days of SZC/PAT treatment and the second after a 2-week washout.

Eighteen KTx patients (8 SZC, 10 g/day vs. 10 PAT, 8.4 g/day) were included and provided two valid DXA-scans (mean age 63 ± 12 years, 12 males). The change in LS BMD determinations in the SZC group was 2.48 ±12.21%, while there was no change in the PAT group, -0.25 ± 2.28%. The absolute root mean squared difference (RMSD) change was 0.102 ± 0.084 g/cm² and 0.021 ±0.013 g/cm² after SZC and PAT washout, respectively (p = 0.008).

In KTx, treatment with SZC, but not PAT, significantly influenced the DXA-scan interpretation of the LS region. After a 2-week washout period, SZC interference was without clinical implications on DXA-scans.

The potassium lowering drug sodium zirconium cyclosilicate (Lokelma) is radiopaque and therefore acts as a confounder on DXA interpretations in kidney transplant recipients. Patiromer (PAT, Veltassa) has no such effect.