How to manage hyperkalemia in a patient on Zytiga (abiraterone) and Prednisone (5 mg bid)?

From the Guidelines

Managing hyperkalemia in a patient on Zytiga (abiraterone) and prednisone (5 mg bid) requires a multifaceted approach, with the most recent and highest quality study suggesting that patiromer (Veltassa) 8.4g daily can be used to manage hyperkalemia 1.

Key Considerations

• Assess the severity of hyperkalemia and consider temporarily reducing the abiraterone dose or briefly interrupting therapy if potassium levels exceed 5.5 mEq/L.
• Ensure the patient is consistently taking their prescribed prednisone, as this corticosteroid helps counteract abiraterone's mineralocorticoid effects that cause potassium retention.
• Dietary modifications are essential, including restricting potassium intake by limiting foods such as bananas, oranges, potatoes, and tomatoes.
• For acute management of significant hyperkalemia (>6.0 mEq/L), consider administering sodium polystyrene sulfonate (Kayexalate) 15-30g orally or patiromer (Veltassa) 8.4g daily.
• Loop diuretics like furosemide 20-40mg daily may help increase potassium excretion.
• Regular monitoring of serum potassium levels is crucial, initially weekly until stabilized, then monthly.

Rationale

Abiraterone inhibits CYP17, reducing cortisol production and increasing mineralocorticoid activity, which leads to sodium retention and potassium excretion impairment. Prednisone supplementation normally counteracts this effect, but some patients may require dose adjustment or additional interventions to maintain normal potassium levels. The use of patiromer (Veltassa) 8.4g daily has been shown to be effective in managing hyperkalemia, allowing for optimization of RAASi therapy and more effective management of hyperkalemia 1.

Additional Considerations

• Monitoring serum K+ should be individualized, with increased frequency of monitoring considered for patients with chronic kidney disease, diabetes, heart failure, or a history of hyperkalemia and for those receiving RAASi therapy 1.
• The availability of newer K+-binding agents, such as patiromer sorbitex calcium and sodium zirconium cyclosilicate, may facilitate optimization of RAASi therapy and more effective management of hyperkalemia 1.

From the Research

Management of Hyperkalemia

To manage hyperkalemia in a patient on Zytiga (abiraterone) and Prednisone (5 mg bid) with a potassium level of 5.6 mmol/L, consider the following:

• The patient's medication regimen should be reevaluated, and any medications that may be contributing to hyperkalemia should be discontinued if possible 2.
• For patients with less severe hyperkalemia, renal elimination drugs or gastrointestinal elimination drugs may be used 2.
• Newer potassium binders, such as patiromer and sodium zirconium cyclosilicate, may be effective in chronic or acute hyperkalemia 3, 4.
• Fludrocortisone therapy may be considered in patients with Type 4 renal tubular acidosis and recurrent hyperkalemia, although there is limited evidence for its use in this setting 5.

Treatment Options

Treatment options for hyperkalemia include:

• Intravenous calcium, insulin, and inhaled beta agonists for urgent management 2, 3, 4.
• Hemodialysis for severe cases or in patients with end-stage renal disease 2, 3, 4.
• Potassium binders, such as patiromer and sodium zirconium cyclosilicate, for chronic or acute hyperkalemia 3, 4.
• Renal elimination drugs or gastrointestinal elimination drugs for less severe hyperkalemia 2.

Monitoring and Prevention

It is essential to monitor the patient's potassium levels and adjust the treatment plan as needed. Additionally, addressing the underlying cause of hyperkalemia and providing dietary counseling can help prevent future episodes 4.