Potassium binders may help solid-organ transplant (SOT) recipients control hyperkalemia over the short term, according to 2 small case series presented at the American Transplant Society 2020 virtual congress.

In the first series, 37 SOT recipients (73% kidney, 21% liver, 3% kidney-pancreas, and 3% lung) started on patiromer, a potassium-calcium cation exchange polymer, at a median 165 days after transplant (and as early as 10 days). Mean serum potassium levels declined significantly from 5.4 mEq/L at baseline to 5.0 and 4.8 mEq/L at 4 and 12 weeks, respectively, Priyamvada Singh, MBBS, and colleagues from Ohio State University in Columbus, reported. A total of 72% and 73% of patients had achieved a goal potassium level of less than 5.2 mEq/L at 4 and 12 weeks, respectively. Many recipients reached target levels within a median 9 days. Virtually all patients continued at the 8.4 g/day dose throughout patiromer treatment with just 1 patient requiring a dose escalation to 25.2 g/day.

With respect to side effects, the team observed a significant increase in mean tacrolimus concentration, from 6.9 ng/mL at baseline to 8.3 ng/mL at 4 weeks, with 32% of patients requiring a tacrolimus dose reduction, Dr Singh said during a video presentation. Cyclosporine levels at baseline and 4 weeks did not differ significantly. There were no reported incidences of bowel necrosis. Most patiromer users had no gastrointestinal adverse events, except for occasional constipation in 8%. Nearly two-thirds of patients experienced hypomagnesemia, which was likely due to the concomitant use of calcineurin inhibitors (CNIs) leading to renal wasting.

Nearly half of patients discontinued patiromer at the end of the study due to hyperkalemia resolution, insurance noncoverage, side effects, and cost. Insurance coverage was obtained for 81% of patients with the remainder using patient-assistance programs.


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Patiromer is moderately effective in controlling potassium in SOT recipients, Dr Singh concluded. “We didn’t encounter any safety issues,” she added. “Hypomagnesemia is the commonest electrolyte abnormality and may require some magnesium supplementation.”

In addition, transplant providers should be aware of possible rises in tacrolimus levels.

In a second study, Ryan Winstead, PharmD, BCPS, and colleagues from VCU Health in Richmond, Virginia, examined the use of sodium zirconium cyclosilicate in 35 SOTs (46% kidneys, 40% livers, 6% hearts, 6% kidney-liver, and 3% kidney-heart). Sodium zirconium cyclosilicate, which binds potassium in exchange for sodium and hydrogen, was initiated at a median 75 days from transplant (and no less than 7 days). Patients took the drug 2 hours apart from other medications at a dosing frequency ranging from once daily to 3 times daily for 34% of patients who had severe hyperkalemia (mean 6.2 mEq/L).

Sodium zirconium cyclosilicate significantly reduced serum potassium by a mean 1.3 mEq/L over 7 days from a mean 5.9 mEq/L, the investigators reported. Over the brief period, tacrolimus concentration decreased by 0.54 ng/mL, whereas sodium and bicarbonate concentrations increased by 1.70 and 1.60 mEq/L, respectively. The most common reasons for drug discontinuation were hyperkalemia resolution and discontinuation of sulfamethoxazole/trimethoprim. Mild edema developed in 2 patients.

According to Dr Winstead’s team, sodium zirconium cyclosilicate lowered serum potassium over 7 days in transplant recipients on calcineurin inhibitors with no apparent significant impact on tacrolimus drug pharmacokinetics.

References

Singh P, Winters H, Pesavento TE, Schnelle K. Largest experience of safety, and efficacy of patiromer in solid organ transplants (SOT). Presented at the American Transplant Society 2020 virtual congress held May 29 to 31. Am J Transplant. 2020; 20 (suppl 3). Abstract 609.

Winstead R, Demehin M, Yakubu I, Song C, et al. Sodium zirconium cyclosilicate use in solid organ transplant recipients and its effect on potassium and immunosuppression. Am J Transplant. 2020; 20 (suppl 3). Abstract D-220.