What are the side effects of telmisartan (angiotensin II receptor antagonist)?

Side Effects of Telmisartan

Telmisartan is generally well-tolerated with a side effect profile similar to placebo, with the most common adverse effects being sinusitis (3%), back pain (3%), and diarrhea (3%). 1

Serious Side Effects Requiring Immediate Medical Attention

Fetal Toxicity (Black Box Warning)

• Telmisartan can cause injury or death to an unborn baby and must be discontinued immediately if pregnancy is detected. 1
• Women of childbearing age should discuss alternative antihypertensive options if planning pregnancy 1

Hypotension

• Low blood pressure is most likely in patients who are volume-depleted from diuretics, low-salt diets, dialysis, heart problems, or acute vomiting/diarrhea 1
• Patients experiencing faintness or dizziness should lie down and contact their physician immediately 1

Renal Dysfunction

• Kidney problems may worsen in patients with pre-existing renal disease 1
• Monitor for swelling in feet, ankles, or hands, and unexplained weight gain 1
• Changes in kidney function tests may necessitate dose reduction 1
• Dual blockade of the renin-angiotensin system (with ACE inhibitors, other ARBs, or aliskiren) significantly increases risk of acute renal failure, hyperkalemia, and hypotension 1

Hyperkalemia

• Elevated potassium levels require periodic monitoring, particularly in patients with renal impairment or diabetes 1

Allergic Reactions

• Rare but serious allergic reactions include swelling of face, tongue, or throat, difficulty breathing, and skin rash 1
• Only one case of angioedema was reported among 3,781 patients in initial clinical trials 1

Common Side Effects (≥1% incidence)

The following adverse events occurred more frequently with telmisartan than placebo in controlled trials of 1,455 patients: 1

• Upper respiratory tract infection (7% vs 6% placebo)
• Back pain (3% vs 1% placebo)
• Sinusitis (3% vs 2% placebo)
• Diarrhea (3% vs 2% placebo)
• Pharyngitis (1% vs 0% placebo)

Additional Adverse Events (>0.3% incidence)

• Cardiovascular: Peripheral edema, leg edema, abnormal ECG 1
• Central nervous system: Insomnia, somnolence, migraine, vertigo, paresthesia, involuntary muscle contractions 1
• Gastrointestinal: Flatulence, constipation, gastritis, vomiting, dry mouth 1
• Metabolic: Gout, hypercholesterolemia, diabetes mellitus 1
• Musculoskeletal: Arthritis, arthralgia, leg cramps 1
• Psychiatric: Anxiety, depression, nervousness 1
• Respiratory: Asthma, bronchitis, rhinitis, dyspnea, epistaxis 1
• Dermatologic: Dermatitis, rash, eczema, pruritus 1

Photosensitivity

• Telmisartan is associated with drug-induced photosensitivity reactions 2
• Patients should seek shade during midday hours, wear protective clothing and broad-brimmed hats, and apply broad-spectrum sunscreen with SPF 30 or higher 2
• Ultraviolet radiation exposure is intensified by reflection from water, sand, or snow 2

Laboratory Abnormalities

• Hemoglobin: Decreases >2 g/dL occurred in 0.8% of patients (vs 0.3% placebo), but no discontinuations due to anemia 1
• Creatinine: Increases ≥0.5 mg/dL occurred in 0.4% of patients (vs 0.3% placebo) 1
• Liver enzymes: Occasional elevations occurred but at lower frequency than placebo; no discontinuations due to hepatic dysfunction 1

Discontinuation Rates

• Only 2.8% of patients discontinued telmisartan due to adverse events in placebo-controlled trials, compared to 6.1% with placebo 1
• In the TRANSCEND cardiovascular risk reduction trial, discontinuation rates were 8.4% with telmisartan versus 7.6% with placebo over 4.8 years 1

Notable Absence of Common ARB Side Effects

• Cough incidence with telmisartan (1.6%) was identical to placebo, a significant advantage over ACE inhibitors 1, 3
• Adverse events were not dose-related and did not correlate with gender, age, or race 1

Drug Interactions Requiring Monitoring

• Aliskiren: Contraindicated in diabetic patients; avoid in renal impairment (GFR <60 mL/min/1.73 m²) 1
• Lithium: Requires monitoring due to potential toxicity 1
• Digoxin: May require monitoring 1
• NSAIDs: May reduce antihypertensive effect and worsen renal function 1
• Diuretics: Increase risk of hypotension 1

Clinical Pitfalls to Avoid

• Do not combine telmisartan with other RAS inhibitors (ACE inhibitors, other ARBs, or aliskiren) as this increases risks without additional benefit 1
• Monitor renal function and electrolytes closely when initiating therapy, particularly in elderly patients or those with pre-existing renal disease 1
• Ensure adequate hydration in patients taking concurrent diuretics or those at risk for volume depletion 1
• Breastfeeding is not recommended as it is unknown whether telmisartan passes into breast milk 1