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telmisartan: what international guidelines say – evidence review – Evigrade

Drug–drug interactions

9 pairs found. Sorted from critical to minor.

Major

Captopril

ACE inhibitor

Mechanism

Dual RAAS blockade (ACE-I + ARB). The ONTARGET trial showed increased hyperkalaemia, hypotension, and acute kidney injury without outcome improvement. Contraindicated in most clinical situations.

Symptoms

Muscle weakness, paraesthesia, slowed pulse, arrhythmias. ECG: peaked T waves, widened QRS. Severe cases progress to cardiac arrest.

Management

The combination is not prescribed. Choose one: ACE-I (captopril) if tolerated, ARB (telmisartan) if there is a dry cough.

Sources

ONTARGET Investigators: Telmisartan, Ramipril, or Both in Patients at High Risk for Vascular Events (2008)

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Major

Co-trimoxazole

Sulfonamide-trimethoprim combination

Mechanism

Trimethoprim in co-trimoxazole blocks the epithelial sodium channel (ENaC) like amiloride – potassium retention. With an ARB (telmisartan): additive hyperkalaemia.

Symptoms

Muscle weakness, paraesthesia, slowed pulse, arrhythmias. ECG: peaked T waves, widened QRS. Severe cases progress to cardiac arrest.

Management

During co-trimoxazole therapy, check potassium 3 days after start. In older patients and chronic kidney disease, prefer alternative antibiotics (nitrofurantoin, fosfomycin).

Sources

BMJ: Co-trimoxazole, sudden death and RAS blockers — Fralick 2014 (2014)

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Major

Enalapril

Angiotensin-converting enzyme inhibitors (ACEi)

Mechanism

Dual RAAS blockade – increased hyperkalaemia, hypotension, and acute kidney injury without outcome improvement (ONTARGET).

Symptoms

Muscle weakness, paraesthesia, slowed pulse, arrhythmias. ECG: peaked T waves, widened QRS. Severe cases progress to cardiac arrest.

Management

The combination is not prescribed. Choose one: ACE-I (enalapril) if tolerated, ARB (telmisartan) if there is a dry cough.

Sources

ONTARGET Investigators: Telmisartan, Ramipril, or Both in Patients at High Risk for Vascular Events (2008)

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Major

Ibuprofen

Non-steroidal anti-inflammatory drugs (NSAIDs)

Mechanism

Similar to losartan + ibuprofen. NSAIDs reduce renal blood flow; the ARB (telmisartan) lowers glomerular pressure. The combination causes acute kidney injury.

Symptoms

Reduced urine output, rising creatinine and potassium, oedema. Symptoms appear earlier in older patients and in chronic kidney disease.

Management

Avoid prolonged combination. If ibuprofen is needed for a short course, use the minimum effective dose for 5–7 days with pantoprazole cover and creatinine monitoring. For chronic analgesia: paracetamol or celecoxib.

Sources

FDA: Micardis section 7 (2014)

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Major

Spironolactone

Potassium-sparing diuretics (mineralocorticoid receptor antagonists)

Mechanism

Additive hyperkalaemia. Both drugs retain potassium: spironolactone directly blocks aldosterone receptors; telmisartan (ARB) reduces aldosterone synthesis.

Symptoms

Muscle weakness, paraesthesia, slowed pulse, arrhythmias. ECG: peaked T waves, widened QRS. Severe cases progress to cardiac arrest.

Management

The combination is appropriate in heart failure with reduced ejection fraction. Check potassium and creatinine 1 week after start, then monthly. If potassium exceeds 5.5 mmol/L, reduce the dose of one agent.

Sources

ESC: 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure (2021)

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Moderate

Acetylsalicylic acid

Antiplatelet agents (low dose) / NSAIDs (analgesic dose)

Mechanism

High aspirin doses (above 1 g/day) may reduce the ARB's antihypertensive effect via vasodilator prostaglandin suppression. Cardioprotective doses (75–100 mg) are clinically minor.

Symptoms

Gradual blood pressure rise at high aspirin doses. At cardioprotective doses, no significant changes.

Management

Cardioprotective aspirin doses (75–100 mg) are acceptable without adjustment. At high doses, monitor blood pressure and increase telmisartan if needed. Alternative analgesic: paracetamol.

Sources

FDA: Micardis section 7 (2014)

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Moderate

Alprazolam

Benzodiazepines. Short-to-medium-acting anxiolytics

Mechanism

Additive hypotension. Benzodiazepines have weak hypotensive effect; the main one comes from the ARB. In most patients, clinically minor.

Symptoms

Postural dizziness, syncope, fatigue. Older patients: fall and fracture risk. Morning weakness possible at standard doses.

Management

No dose adjustment usually needed. In older patients on starting telmisartan, check standing/sitting BP at one week. With pronounced morning hypotension, move alprazolam from night to morning or switch to buspirone.

Sources

FDA: Micardis section 7 (2014)

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Moderate

Amitriptyline

Tricyclic antidepressants (TCA)

Mechanism

Additive hypotension, especially orthostatic. Amitriptyline blocks α1-adrenoceptors; telmisartan is an ARB. Effects add up.

Symptoms

Postural dizziness, syncope, fatigue. Older patients: fall and fracture risk.

Management

On starting the combination, begin amitriptyline at 10 mg at bedtime. In older patients, do not exceed 25 mg/day. Check standing/sitting BP at 1–2 weeks. For neuropathic pain, alternatives: gabapentin or pregabalin.

Sources

FDA: Micardis section 7 (2014)

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Moderate

Digoxin

Cardiac glycosides (digitalis)

Mechanism

Telmisartan moderately inhibits intestinal P-glycoprotein. Digoxin AUC rises by 20–50%, which may trigger toxicity, especially in older patients and in chronic kidney disease.

Symptoms

Nausea, vomiting, loss of appetite, confusion, yellow-green halos around lights, arrhythmia (bigeminy, AV block). Symptoms appear earlier in older patients and chronic kidney disease.

Management

On telmisartan start, check digoxin levels at 1–2 weeks. In significant chronic kidney disease (clearance below 50 mL/min), reduce digoxin by 25%. In older patients, target 0.5–0.8 ng/mL. Alternatives: losartan or valsartan, with less effect on P-glycoprotein.

Sources

FDA: Micardis section 7 (2014)

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