A 64-year-old man comes to the office for follow-up of hypertension. At the last 2 visits, his blood pressure was persistently elevated. The patient has been treated with lisinopril for the past 5 years, but his other blood pressure medications have been changed several times due to various adverse effects. Medical history is significant for type 2 diabetes mellitus, coronary artery disease with stable angina, and moderately increased albuminuria. Blood pressure is 145/87 mm Hg and pulse is 70/min. BMI is 31 kg/m². Physical examination shows trace bilateral lower extremity edema. ECG is unremarkable. Serum laboratory results are as follows: Review of the patient's medical records shows similar serum laboratory results 6 months ago. Which of the following medications should be avoided in this patient?

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11ec160b_3b8d_c250_9249_9d69e7587034_MD0001_00 This patient with diabetes complicated by albuminuria, coronary artery disease (CAD), and hypertension is being appropriately treated with an ACE inhibitor (eg, lisinopril). ACE inhibitors block the conversion of angiotensin I to angiotensin II, leading to decreased systemic vascular tone, reduced aldosterone secretion, and lowered blood pressure. Decreased aldosterone levels cause increased sodium excretion and potassium retention, which can lead to hyperkalemia. The risk is greatest in patients with renal insufficiency and those taking potassium-sparing diuretics or medications that decrease glomerular filtration (eg, nonsteroidal anti-inflammatory drugs). Mineralocorticoid receptor blockers (eg, spironolactone, eplerenone), angiotensin II receptor blockers (eg, losartan), and epithelial sodium channel blockers (eg, amiloride, triamterene) are other antihypertensives that can raise potassium levels. Concurrent use with an ACE inhibitor can result in severe hyperkalemia and should be avoided in this patient with mild hyperkalemia at baseline. (Choices A and C) Dihydropyridine calcium channel blockers (eg, amlodipine, nifedipine) inhibit the L-type calcium channel on vascular smooth muscle, leading to arterial vasodilation. Nondihydropyridine calcium channel blockers (eg, verapamil) reduce heart rate and contractility. Diltiazem causes both vasodilation and decreased heart rate and contractility. Calcium channel blockers do not cause significant electrolyte abnormalities and may be used in patients at risk for hyperkalemia. Although dihydropyridine calcium channel blockers may cause lower extremity edema, trace pedal edema is extremely common and not a contraindication for use. (Choices B and E) Loop diuretics (eg, bumetanide, furosemide) inhibit the Na⁺/K⁺/2Cl^- symporter in the ascending limb of the loop of Henle. They decrease intravascular volume, leading to an increase in serum aldosterone and a resultant increase in urinary potassium excretion, causing hypokalemia. (Choice F) Metoprolol is a selective beta-1 blocker that decreases heart rate, cardiac contractility, and renin release, which reduces arterial blood pressure and myocardial oxygen demand. Although nonselective beta blockers (eg, carvedilol) can cause hyperkalemia by inhibiting beta-2-mediated intracellular potassium uptake, this does not typically occur with selective beta-1 blockers. Although beta blockers can mask hypoglycemia in diabetic patients, this is not a contraindication and they can still be used (cautiously) in patients with CAD to reduce myocardial oxygen demand. Educational objective: ACE inhibitors block the conversion of angiotensin I to angiotensin II, thereby reducing vasoconstriction and aldosterone secretion. Decreased aldosterone leads to potassium retention, which can cause hyperkalemia, especially in patients with renal insufficiency and those taking other medications that raise potassium levels (eg, angiotensin II receptor blockers, mineralocorticoid receptor blockers). __________ References: Renin-angiotensin-aldosterone system blockade for cardiovascular diseases: current status. (http://www.ncbi.nlm.nih.gov/pubmed/20590619) Drug-induced hyperkalemia. (http://www.ncbi.nlm.nih.gov/pubmed/25047526)

A 64-Year-Old Man Comes to the Office for Follow-Up of Hypertension