Potassium, oral

Common indications

• Treatment and prevention of potassium depletion. This is usually evident from a low serum potassium concentration (hypokalaemia). Addition of a drug with potassium-sparing diuretic effects is preferred when potassium losses are due to loop- or thiazide-diuretic therapy. Intravenous potassium chloride is preferred in the initial treatment of hypokalaemia that is severe (<2.5 mmol/L), symptomatic, or causing arrhythmias.

 

Mechanisms of action

• Hypokalaemia is usually, although not always, due to potassium depletion. This may be because of, for example, diarrhoea, vomiting, or secondary hyperaldosteronism. Potassium supplementation may restore normal potassium balance in this scenario. 
• By contrast, if losses are due to loop- or thiazide-diuretic therapy, supplementation is largely ineffective. This is because although the serum potassium concentration is low, intake and output are in balance. Potassium supplementation results simply in increased potassium excretion and only minimal effect on serum concentration. Treatment with a potassium-sparing diuretic (or aldosterone antagonist) is therefore preferred. 
• In redistributive hypokalaemia the total body potassium content is normal, but the serum concentration is low because of redistribution into cells. Drug therapy (e.g. with insulin, salbutamol) is most often the culprit. Management should ideally be to address the underlying cause.

 

Important adverse effects

• Oral potassium preparations are not very well tolerated, mainly because they are unpalatable and cause gastrointestinal disturbance, including nausea, vomiting, pain, diarrhoea and flatulence. 
• Modified-release preparations may be better tolerated, but these can cause gastrointestinal obstruction, ulceration and bleeding. 
• Overtreatment may lead to hyperkalaemia and a resultant risk of arrhythmias.

 

Warnings

• Potassium supplements must be used with caution (lower dose and more intensive monitoring) in patients with renal impairment, due to the greatly increased risk of hyperkalaemia. 
• They should be avoided in severe renal impairment.

 

Important interactions

• Oral potassium supplements have additive effects with other potassium-elevating drugs, including intravenous potassium chloride, aldosterone antagonists, potassium-sparing diuretics, ACE inhibitors and angiotensin receptor blockers.