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Updated September 01, 2015.

A new drug called Patiromer has shown promise in treating hyperkalemia in people who are taking renin-angiotensin-aldosterone system (RAAS) inhibitors.  Hyperkalemia is life threatening and results in weakness, ascending paralysis, respiratory failure and cardiac abnormalities.

Sometimes, people present with hyperkalemia, or heightened levels of potassium in the blood, in outpatient clinics.  These people are older and commonly with diabetic kidney disease and present with hyperkalemia after having taken renin-angiotensin-aldosterone system (RAAS) inhibitors (ß-blockers, angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers [ARBs], and aldosterone receptor antagonists)   In such patients with baseline renal impairment or diabetic nephropathy, potassium levels can be increased to dangerous levels after administration of RAAS inhbitiors, which spare potassium from excretion in the urine.


 

Mostly, however, hyperkalemia is something that more commonly presents among hospitalized patients treated with RAAS inhibitors for heart failure, diabetes and chronic kidney disease. Diabetes and chronic kidney disease result in atherosclerosis and glomerulosclerosis, respectively; these pathological processes work together to inhibit the body's (kidney's) ability to rid itself of potassium. 

Although RAAS inhibitors are potassium sparing and can result in higher levels of potassium or hyperkalemia, heart failure, chronic kidney disease and diabetes are treated with RAAS inhibitors.  Thus, it would be useful to find a more effective way to treat hyperkalemia in people with these conditions who are taking RAAS inhibitors. 

Currently, hyperkalemia has been only treated with temporary measures like like beta agonists, calcium, or insulin and glucose, all of which move potassium into cells; loop or thiazide diuretics, both of which are potassium wasting and increase the excretion of potassium; a drug called sodium polysterene sulfonate (Kayexalate), which can cause hypomagnesemia, hypokalemia, severe gastrointestinal distress and even bowel necrosis; and dialysis.

  During Phase 3 clinical trials, Patiromer significantly reduces potassium levels in patients with diabetic kidney disease who were taking RAAS inhibitors and developed mild to severe hyperkalemia.

Patiromer is made of a polymer which passes through the gastrointestinal tract unabsorbed.  While passing through the gastrointestinal tract, it sucks up potassium.  In clinical trials, Patiromer was shown to be safe and effective for an entire 52 weeks in people with hyperkalemia and diabetes, which suggests that it's a promising maintenance therapy.  In other words, people taking RAAS inhibitors can avoid hyperkalemia by taking Patiromer.  Moreover, after participants stopped taking Patiromer, they rapidly developed hyperkalemia once again. On a related note, in other studies, Patiromer has also been shown to prevent hyperkalemia in people with heart failure who were taking RAAS inhibitors.

Patients taking Patiromer did report some adverse effects including worsening of chronic kidney disease, hypomagnesemia, worsening of hypertension and gastrointestinal distress.  Overall, however, only 10 percent of the participants in this study discontinued taking Patiromer because of these adverse effects.

Despite the promise shown by Patiromer during Phase 3 clinical trials, some experts have voiced concerns over the drug.  First, these experts point out that it would be a good idea to continue testing of Patiromer for longer than a year--after all, some people will need to spend the remainder of their lives on Patiromer while receiving RAAS inhibitors.  Second, it's unclear whether people taking RAAS inhibitors and Patiromer for hyperkalemia benefit from treatment with RAAS inhibitors as much as those with normal levels of potassium (normokalemia) who are taking RAAS inhibitors.

<sub>Selected Sources

Article titled "Effect of Patiromer on Serum Potassium Level in Patients With Hyperkalemia and Diabetic Kidney Disease The AMETHYST-DN Randomized Clinical Trial" by GL Bakris and co-authors published in JAMA in 2015.  Accessed 8/24/2015.

Article titled "Treatment of Hyperkalemia From “Hyper K+” Strikeout to Home Run?" by WC Winklemayer published in JAMA in 2015.  Accessed 8/24/2015.</sub>