New Drugs to Treat Hyperkalemia

Patiromer, a new potassium binder, was approved by the FDA in 2015. This sodium-free, nonabsorbed, spherical polymer uses calcium as the exchange cation to bind potassium in the gastrointestinal tract. Its onset of action is seven hours, with a 24-hour duration of action. It is not approved for emergency use. There are no renal dosing adjustment considerations with patiromer.

In RCTs, patiromer has been associated with a significant reduction in serum potassium in patients with CKD (with or without diabetes) taking RAAS therapy. The starting dose is 8.4 g/d mixed with water, taken with food; this can be increased by 8.4 g each week as needed, to a maximum dosage of 25.2 g/d. Patiromer binds between 8.5 mEq to 8.8 mEq of potassium per gram of polymer.

The original approval included a black box warning to take patiromer six hours before and after other medications, due to concern for binding with certain medications. However, after an additional study in 2016, the FDA removed this warning and approved a change in administration to three hours before and after taking other medications.

Use of patiromer is not advised in those with severe constipation, bowel obstruction/impaction, or allergies to any of its components.¹¹ Adverse reactions associated with patiromer include constipation (which generally improves with time), hypomagnesemia, diarrhea, nausea, abdominal discomfort, and flatulence. A 52-week RCT of 304 patients with CKD on RAAS found the most common adverse event to be mild-to-moderate constipation (6.3% of patients), with two patients discontinuing therapy as a result.⁴ In clinical trials, 9% of patients developed hypomagnesemia (serum magnesium value, < 1.4 mg/dL). It is recommended that serum magnesium levels be monitored and supplementation offered, when appropriate.¹¹

Sodium zirconium cyclosilicate (ZS-9) is among the potassium-lowering medications on the horizon. In 2016, the FDA accepted a new drug application for this insoluble, unabsorbed cation exchanger that also works in the GI tract and uses sodium and hydrogen as exchange cations.¹²

For now, however, dietary education remains a mainstay of treatment for patients with elevated serum potassium levels. It is particularly important to inform your patients that many salt substitutes and low-sodium products contain potassium chloride. They should therefore exercise caution when incorporating sodium-reducing components into their diet. —CS

Cynthia Smith, DNP, CNN-NP, APRN, FNP-BC
Renal Consultants, PLLC, South Charleston, West Virginia