From the Guidelines
Losartan can cause several side effects, including dizziness, lightheadedness, fatigue, and headache, as well as more serious effects like low blood pressure and high potassium levels, as noted in the 2018 guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1.
Common Side Effects
- Dizziness and lightheadedness, which typically occur as the body adjusts to the medication
- Fatigue and headache
- Upper respiratory infections, cough, or nasal congestion
- Digestive issues such as diarrhea, stomach pain, or nausea
Serious Side Effects
- Low blood pressure (hypotension), which can cause severe dizziness or fainting, especially when standing up quickly
- High potassium levels (hyperkalemia), which can cause irregular heartbeat or muscle weakness
- Allergic reactions with symptoms like rash, itching, or swelling of the face, lips, or tongue
- Kidney problems or liver dysfunction, although these are rare
Rare but Serious Side Effects
- Jaundice, dark urine, persistent nausea, or signs of an allergic reaction, which require immediate medical attention The Losartan Intervention for Endpoint Reduction in Hypertension (LIFE) Study compared the effects of an angiotensin II type 1 receptor blocker with a β-adrenergic receptor blocker in patients with essential hypertension and electrocardiographically determined LV hypertrophy, and found that losartan was effective in reducing major vascular events 1.
Patient Guidance
- Patients should be aware of the potential side effects of losartan and seek medical attention if they experience any severe or persistent symptoms
- Regular monitoring of blood pressure, kidney function, and electrolyte levels is recommended to minimize the risk of side effects
- Losartan should be used with caution in patients with a history of angioedema or those taking other medications that may interact with it, as noted in the guideline 1.
From the FDA Drug Label
In 4 clinical trials involving over 1000 patients on various doses (10 to 150 mg) of losartan potassium and over 300 patients given placebo, the adverse events that occurred in ≥2% of patients treated with losartan and more commonly than placebo were: dizziness (3% vs. 2%), upper respiratory infection (8% vs. 7%), nasal congestion (2% vs. 1%), and back pain (2% vs 1%). The following less common adverse reactions have been reported:
- Blood and Lymphatic System Disorders: Anemia.
- Psychiatric Disorders: Depression.
- Nervous System Disorders: Somnolence, headache, sleep disorders, paresthesia, migraine.
- Ear and Labyrinth Disorders: Vertigo, tinnitus.
- Cardiac Disorders: Palpitations, syncope, atrial fibrillation, CVA
- Respiratory, Thoracic and Mediastinal Disorders: Dyspnea.
- Gastrointestinal Disorders: Abdominal pain, constipation, nausea, vomiting.
- Skin and Subcutaneous Tissue Disorders: Urticaria, pruritus, rash, photosensitivity.
- Musculoskeletal and Connective Tissue Disorders: Myalgia, arthralgia.
- Reproductive System and Breast Disorders: Impotence
- General Disorders and Administration Site Conditions: Edema. The most common side effects of Losartan Potassium Tablets in people with high blood pressure are:
- “colds” (upper respiratory infection)
- dizziness
- stuffy nose
- back pain The most common side effects of Losartan Potassium Tablets in people with type 2 diabetes with diabetic kidney disease are:
- diarrhea
- tiredness
- low blood sugar
- chest pain
- high blood potassium
- low blood pressure
The side effects of losartan include:
- Common side effects: dizziness, upper respiratory infection, nasal congestion, back pain, diarrhea, tiredness, low blood sugar, chest pain, high blood potassium, low blood pressure
- Less common side effects: anemia, depression, somnolence, headache, sleep disorders, paresthesia, migraine, vertigo, tinnitus, palpitations, syncope, atrial fibrillation, CVA, dyspnea, abdominal pain, constipation, nausea, vomiting, urticaria, pruritus, rash, photosensitivity, myalgia, arthralgia, impotence, edema 2 2 It is essential to note that this list may not be exhaustive, and patients should be aware of the potential for other side effects not mentioned here. If a side effect bothers you or won't go away, you should tell your doctor. 2
From the Research
Side Effects of Losartan
- The side effects of losartan have been reported to be very few in clinical trials, with a rate similar to that of placebo 3
- Common side effects include dizziness, which was the only drug-related event reported more frequently with losartan potassium monotherapy than with placebo 4
- Losartan may cause hyperkalemia when used with potassium-sparing diuretics, such as spironolactone or triamterene 3
- Angioedema and acute hepatitis have been reported in a few patients among thousands of millions of hypertensives under losartan treatment, although the etiology was unclear 3
- Losartan should not be administered to pregnant women and breast-feeding mothers, as it may disturb fetal growth or be harmful to the newborn 3
- It should be cautiously used in patients with renal failure or liver dysfunction 3
Rare but Serious Side Effects
- Losartan has been associated with a reduced incidence of cough compared to ACE inhibitors 4, 5
- Proteinuria was decreased in 3 out of 4 patients treated with losartan 6
- Losartan may retard the progression of advanced renal insufficiency, as suggested by a significant reduction in the slope of reciprocal serum creatinine plotted against time 6
Special Considerations
- Losartan is well tolerated, with an adverse effect profile similar to that of placebo 4, 5
- The combination product of losartan and hydrochlorothiazide has a similar adverse effect profile to losartan monotherapy and placebo 4
- Losartan may be an alternative for patients who cannot tolerate ACE inhibitors 5