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Clinician’s Corner: Drugs that affect calcium and potassium

One of my former Physician Students asked me for my next column to write about drugs that affect calcium and potassium. As you can see from the list below, your Thompson Pharmacist is extremely helpful in assisting your physician, if drug therapy makes your bloodwork go “out of whack”!

Drugs causing HYPERCALCEMIA (HIGH CALCIUM LEVELS)

THIAZIDE DIURETICS

Hydrochlorothiazide, chlorthalidone

Cause calcium retention by increased resorption of calcium in renal tubules.
Calcipotriol (Dovonex ®) Caution with high doses or in patients with severe, extensive psoriasis
Lithium (Eskalith) Usually mild, likely due to increased secretion of parathyroid hormone (PTH). May take 4 weeks post lithium to resolve
Excessive Calcium Supplementation Obviously!
Theophylline toxicity Results in mild hypercalcemia


DRUGS CAUSING HYPERKALEMIA (HIGH POTASSIUM LEVELS)

Potassium-sparing diuretics (triamterene, amiloride) Block directly the K+-Na+ exchange in the collecting tubules.
Aldosterone antagonist (spironolactone/epleronone) compete with aldosterone for receptor sites
NSAIDs

(Motrin, Naproxen, Celebrex)

By inhibiting renal function (block afferent vasodilatation of arterioles). May also inhibit renin secretion.
ACE inhibitors  (lisinopril,enalapril,quinapril, etc.) By blocking Angiotensin-II, aldosterone is decreased. Aldosterone increases the excretion of potassium
Angiotensin-receptor blockers (ARBs) (Losartan, Irbesartan etc) By blocking Angiotensin-II, aldosterone is decreased. Aldosterone increases the excretion of potassium
Non Selective beta-blockers  (propranolol, labetalol) interfere with the beta-2-adrenergic facilitation of potassium uptake by the cells.  Selective BB like atenolol (mostly ß-1) have minimal effect. All ß-blockers at high dose lose beta selectivity.
Cyclosporine or tacrolimus

 

due to reduced efficiency of urinary potassium excretion
Trimethoprim-sulfamethoxazole

 

Trimeth blocks apical membrane sodium channels in the mammalian distal nephron, blocking the excretion of K+
Ketoconazole Inhibits aldosterone synthesis
Herbs Alfalfa, Dandelion Horsetail, Nettle are high in potassium
Potassium supplements in excessive doses Obviously!

So, as we can see many of our commonly used drug therapies can have a significant impact on these two very important ions.  The concern becomes even greater in our patients that are elderly or frail.  Your Thompson Pharmacist is the most accessible health care professional!  At Thompson Pharmacy… it’s all for YOU!