Losartan, often known by its brand name Cozaar®, is a type of medication called an angiotensin II receptor blocker (ARB). It is prescribed for several conditions, including high blood pressure (hypertension), diabetic nephropathy (kidney disease in people with type 2 diabetes), and to reduce the risk of stroke in certain heart disease patients. While effective, understanding what are the side effects of losartan is crucial for patients and healthcare providers to ensure safe use and proper management.
Common Side Effects of Losartan
Most side effects associated with losartan are generally mild and tend to diminish as your body adjusts to the medication. It is important to monitor these effects and report persistent or bothersome symptoms to your doctor. Common side effects include:
- Dizziness and lightheadedness: This is one of the most common side effects, especially when first starting the medication or after a dose increase. It occurs because losartan lowers blood pressure, and a sudden drop can cause dizziness. Patients can minimize this by standing up slowly from a sitting or lying position.
- Fatigue or tiredness: A feeling of unusual weakness or low energy is frequently reported.
- Upper respiratory tract infections: Symptoms similar to the common cold, such as a stuffy or runny nose, sore throat, and sneezing, may occur.
- Headache: Mild headaches are a possible side effect, particularly during the first week of treatment.
- Back and joint pain: Some individuals experience muscle or joint aches.
- Mild hyperkalemia: Losartan can cause a slight increase in potassium levels in the blood. For most people, this is not a concern, but it should be monitored, especially if they have kidney issues or take other potassium-altering medications.
- Diarrhea or upset stomach: Digestive issues like nausea and diarrhea are also possible side effects.
Serious and Rare Side Effects
While far less common, some side effects are serious and require immediate medical attention. If you experience any of the following, contact your doctor immediately or seek emergency care.
- Angioedema: This is a severe allergic reaction that causes swelling of the face, tongue, lips, throat, and eyes. It can lead to life-threatening difficulty with breathing or swallowing. The risk of angioedema is lower with losartan compared to ACE inhibitors but is still a possibility, particularly in patients with a history of swelling with ACE inhibitors.
- Severe hyperkalemia: A dangerously high potassium level in the blood can cause muscle weakness, numbness, and an irregular or slow heartbeat. This is more likely in patients with kidney problems, diabetes, or those taking potassium supplements.
- Kidney injury: Losartan can, in rare cases, cause or worsen kidney problems. Symptoms may include a decrease in urination, and swelling in the ankles, hands, or feet.
- Liver problems: Very rare but serious liver damage can cause symptoms like yellowing of the skin or eyes (jaundice) or severe stomach pain.
- Hypotension (low blood pressure): Although losartan is meant to lower blood pressure, it can sometimes drop it too low, causing dizziness, fainting, or blurry vision.
Comparison of Losartan and ACE Inhibitors
Losartan and ACE inhibitors are often used to treat similar conditions. The table below highlights key differences in their side effect profiles, particularly concerning the common dry cough associated with ACE inhibitors. For further details on the mechanism of action, visit the National Institutes of Health (NIH) website.
| Feature | Losartan (ARB) | Lisinopril (ACE Inhibitor) |
|---|---|---|
| Mechanism | Blocks the angiotensin II receptor. | Inhibits the enzyme that produces angiotensin II. |
| Incidence of Dry Cough | Significantly lower. | High incidence due to bradykinin accumulation. |
| Risk of Angioedema | Rare, but possible. | More common due to bradykinin accumulation. |
| Therapeutic Use | Hypertension, diabetic nephropathy, stroke risk reduction. | Hypertension, heart failure, post-myocardial infarction. |
Drug Interactions and Contraindications
Several factors can increase the risk of side effects when taking losartan. Inform your doctor about all medications and supplements you are taking.
Drug Interactions
- Potassium-sparing diuretics: Medications like spironolactone or amiloride, when combined with losartan, can significantly increase potassium levels.
- NSAIDs: Over-the-counter pain relievers such as ibuprofen or naproxen can weaken losartan's blood pressure-lowering effect and increase the risk of kidney problems, particularly in older patients or those with pre-existing kidney issues.
- Lithium: Losartan can increase lithium levels in the blood, potentially leading to toxicity.
- Aliskiren: Combining losartan with aliskiren is not recommended, especially for patients with diabetes or kidney problems, due to increased risks of hypotension, hyperkalemia, and kidney issues.
- Grapefruit juice: It can interfere with the metabolism of losartan, potentially affecting its efficacy.
- Alcohol: Can increase the blood pressure-lowering effect, intensifying dizziness or lightheadedness.
Contraindications
- Pregnancy: Losartan is contraindicated during pregnancy, especially in the second and third trimesters, as it can cause serious injury or death to the fetus.
- Allergy: Anyone with a known hypersensitivity to losartan should not take it.
Strategies for Managing Side Effects
Most mild side effects can be managed with simple adjustments or by communicating with your doctor.
- For dizziness: Stand up slowly. If you feel lightheaded, lie down until you feel better. Avoid driving or operating machinery until you know how losartan affects you.
- For headaches: Stay hydrated and rest. For persistent headaches, consult your pharmacist for an appropriate painkiller.
- For nausea or diarrhea: Try taking your dose with food. Drink plenty of fluids to stay hydrated.
- For back or joint pain: If the pain is unusual or severe, inform your doctor. They may recommend blood tests or alternative pain relief.
- For potassium levels: Avoid using salt substitutes containing potassium and discuss potassium-rich foods with your doctor, especially if you have kidney concerns.
Conclusion
Losartan is a valuable medication for controlling blood pressure and protecting against related complications. While it is generally well-tolerated and poses a lower risk of certain side effects like a persistent dry cough compared to ACE inhibitors, a range of potential common and serious adverse effects must be considered. Patient awareness of these side effects, understanding potential drug interactions, and maintaining open communication with healthcare providers are key to safe and effective treatment. Regular monitoring of blood pressure and kidney function can help ensure long-term health while on losartan therapy.
