Which of the following medications, including telmisartan (Angiotensin II Receptor Blocker (ARB)), pregabalin, and metoprolol, can cause hyperkalemia in an 83-year-old female patient with a history of hypertension, Type 2 Diabetes Mellitus (DM), and impaired renal function?

Which Medications Can Cause Hyperkalemia

Among telmisartan, pregabalin, and metoprolol, only telmisartan (an ARB) can cause hyperkalemia, particularly in this 83-year-old patient with diabetes, hypertension, and impaired renal function—a high-risk profile that demands careful monitoring.

Telmisartan: Primary Culprit for Hyperkalemia

Telmisartan directly causes hyperkalemia through its mechanism of action on the renin-angiotensin-aldosterone system. As an angiotensin II receptor blocker, telmisartan blocks AT1 receptors, which reduces aldosterone secretion and subsequently decreases renal tubular potassium excretion 1. The FDA label explicitly warns that "hyperkalemia may occur in patients on ARBs, particularly in patients with advanced renal impairment, heart failure, on renal replacement therapy, or on potassium supplements, potassium-sparing diuretics, potassium-containing salt substitutes or other drugs that increase potassium levels" 1.

High-Risk Patient Profile

This 83-year-old patient has multiple compounding risk factors that dramatically increase hyperkalemia risk with telmisartan:

• Impaired renal function: The most critical risk factor, as reduced GFR impairs potassium excretion 1, 2
• Type 2 diabetes: Diabetic patients have up to 10% incidence of hyperkalemia with ARB therapy 2
• Advanced age: Elderly patients have reduced glomerular filtration and are particularly susceptible to electrolyte disturbances 2

Treatment with ACE inhibitors and ARBs can cause hyperkalemia, particularly among individuals with reduced glomerular filtration who are at increased risk 3. The 2025 American Diabetes Association guidelines emphasize that "serum creatinine and potassium should be monitored after initiation of treatment with an ACE inhibitor or ARB and monitored during treatment and following uptitration of these medications" 3.

Clinical Evidence and Incidence

Published incidence estimates indicate that up to 10% of patients on ARBs may experience at least mild hyperkalemia, with higher rates in those with chronic renal insufficiency 2. A case report documented "significant hyperkalemia and hyponatremia related to telmisartan/hydrochlorothiazide use in a diabetic patient," demonstrating real-world occurrence even with combination therapy 4.

The combination of ACE inhibitors and ARBs is contraindicated given the lack of added cardiovascular benefit and increased rate of adverse events—namely, hyperkalemia, syncope, and acute kidney injury 3. The ONTARGET trial showed that patients receiving combination telmisartan and ramipril experienced increased incidence of renal dysfunction compared to monotherapy 1.

Pregabalin: No Hyperkalemia Risk

Pregabalin does not cause hyperkalemia. This anticonvulsant/neuropathic pain medication works through calcium channel modulation in the central nervous system and has no direct effects on renal potassium handling or the renin-angiotensin-aldosterone system.

Metoprolol: No Hyperkalemia Risk

Metoprolol, a beta-blocker, does not cause hyperkalemia. In fact, beta-blockers can theoretically decrease potassium excretion through reduced renin release, but this effect is clinically insignificant and does not lead to problematic hyperkalemia in routine practice 5.

Critical Monitoring Recommendations

For this high-risk patient on telmisartan, implement the following monitoring protocol:

• Check serum potassium and creatinine within 2-3 days after initiation or dose changes 3, 5
• Recheck at 7 days, then monthly for the first 3 months 5
• Subsequently monitor every 3-6 months depending on stability 5
• More frequent monitoring is essential given her impaired renal function, diabetes, and advanced age 3, 5

Management Algorithm for Hyperkalemia on Telmisartan

If hyperkalemia develops (K+ >5.5 mEq/L):

• Reduce telmisartan dose by 50% rather than discontinuing entirely to maintain cardioprotective and renoprotective benefits 5
• Consider newer potassium binders (patiromer or sodium zirconium cyclosilicate) to maintain RAAS inhibitor therapy 5
• Discontinue telmisartan only if K+ >6.0 mEq/L or if alternative treatable etiology cannot be identified 5

If K+ >6.0 mEq/L with ECG changes:

• Immediate hospital admission required 5
• IV calcium gluconate for cardiac membrane stabilization 5
• Insulin-glucose and beta-agonists for intracellular potassium shift 5

Common Pitfalls to Avoid

• Do not permanently discontinue telmisartan for mild-moderate hyperkalemia (K+ 5.0-6.0 mEq/L); dose reduction plus potassium binders is preferred to maintain mortality and morbidity benefits in diabetes and hypertension 5
• Avoid combining telmisartan with potassium supplements, potassium-sparing diuretics, or potassium-containing salt substitutes without intensive monitoring 1
• Do not use dual RAAS blockade (ARB + ACE inhibitor or ARB + direct renin inhibitor) as this dramatically increases hyperkalemia risk without additional benefit 3, 1
• Counsel patients to avoid NSAIDs, which can precipitate acute renal failure and severe hyperkalemia when combined with ARBs 3, 5