By William Elliott, MD, FACP, and James Chan, PharmD, PhD
Dr. Elliott is Medical Director, Pharmacy, Northern California Kaiser Permanente, and Assistant Clinical Professor of Medicine, University of California, San Francisco. Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA.
Drs. Elliott and Chan report no financial relationships relevant to this field of study.
A non-absorbed, cation exchange polymer potassium binder has been approved for the treatment of hyperkalemia. The current treatment option is sodium polystyrene sulfonate (SPS), which was approved in 1958. Patiromer is marketed as Veltassa.
INDICATIONS
Patiromer is indicated for the treatment of hyperkalemia.1
DOSAGE
The recommended initial dose is 8.4 g (in 3 oz of water) taken once daily with food.1 The dose may increase by 8.4 g daily as needed at 1-week intervals or longer to obtain desired serum potassium target range. The maximum dose is 25.2 g per day. Patiromer is available as 8.4 g, 16.6 g, and 25.2 g powder packets.
POTENTIAL ADVANTAGES
Patiromer provides an alternative to SPS. It does not exchange potassium for sodium. SPS must be used with caution in patients who cannot tolerate even a small increase in sodium load (e.g., severe congestive heart failure).2 Cases of colonic necrosis have been reported with SPS.
POTENTIAL DISADVANTAGES
Patiromer binds to many orally administered drugs (e.g., amlodipine, furosemide, levothyroxine). The FDA added a boxed warning to the drug’s labeling, recommending a 6-hour window between patiromer administration and any other orally administered medication. It also binds to magnesium, which may lead to hypomagnesemia. It should not be used in patients with severe constipation, bowel obstruction, or impaction, including postoperative bowel motility disorder. Other adverse events include constipation and diarrhea. Hypokalemia occurred in 3% of subjects in the clinical study.3
COMMENTS
Hyperkalemia is generally seen in patients with acute or chronic kidney disease or heart failure and on drugs that inhibit the renin-angiotensin-aldosterone system (RAAAS). Elevated potassium levels can lead to conduction abnormalities and potentially fatal cardiac arrhythmias. Patiromer binds to potassium in the lumen of the colon, resulting in potassium excretion in the feces. The efficacy of patiromer was evaluated in a two-part, single-blind, randomized, withdrawal study.1,3 Those with serum potassium of 5.1 mEq/L to < 5.5 mEq/L started on 8.4 g per day. Those with serum potassium levels of 5.5mEq/L to < 6.5 mEq/L started on 16.8 g per day. The dose was titrated as needed. At week 4, those in the lower potassium group had a reduction of serum potassium of -0.65 mEq/L and those in the higher baseline potassium group -1.23 mEq/L. In the second part of the study, subjects (still receiving RAAS inhibitors) who achieved serum potassium levels of 3.8 mEq/L to < 5.1 mEq/L were randomized to continue patiromer or placebo. At week 4, those on placebo showed an increase of 0.72 mEq/L compared to no change for those randomized to patiromer. Through week 8, 60% on placebo had hyperkalemia recurrence, compared to 15% on patiromer. Six percent of those randomized to patiromer had to discontinue RAAS-inhibitor therapy, compared to 56% for placebo. In a separate study, the effect of patiromer appears to be maintained for 52 weeks.1,4
CLINICAL IMPLICATIONS
Other than discontinuation of RAAS-inhibitors, options for the management of hyperkalemia are limited. SPS can cause serious adverse events and is not ideal for the at-risk population due to the increase in sodium load. Patiromer provides a potentially safer alternative and allows patients to continue their RAAS-inhibitors, although the timing of dosing of other medications potentially may be a problem for some patients, many of whom are on multiple drug regimens. The wholesale cost for patiromer (regardless of strength) is $595 per 30 packets. For Kayexalate, the cost for 30 doses (15 g/dose) is $762.
REFERENCES
- Veltassa Prescribing Information. Relypsa, Inc. January 2016.
- Kayexalate Prescribing Information. Sanofi-Aventis 2009.
- Weir MR, et al. Patiromer in patients with kidney disease and hyperkalemia receiving RAAS inhibitors. N Engl J Med 2015;372:211-221.
- Montaperto AG, et al. Patiromer: A clinical review. Curr Med Res Opin 2016;32:155-164.
Patiromer is indicated for the treatment of hyperkalemia.
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