Losartan Potassium Side Effects: What Are They?

Published May 9th, 2020 by Bridget Reed
Fact Checked by
Chris Riley
Updated Date: Jun 22nd, 2021

If you’re one of the 108 million American adults (about 45 percent of the adult population) currently suffering from high blood pressure, you’re definitely not alone. The “silent killer,” so named because it is the number one contributing cause of cardiovascular-related deaths and many people do not know they have the condition until they experience a heart attack or stroke, is at epidemic levels in the United States. High blood pressure, also called hypertension, is influenced heavily by lifestyle factors, such as not getting enough exercise, high-stress levels, and high-fat diets that are customary for many Americans, but it can also be caused by certain medications and medical conditions. The first step in managing high blood pressure is generally making serious lifestyle changes, like eating right and exercising more, but lifestyle changes alone aren’t enough for everyone to manage their high blood pressure, and prescription drug treatment may be necessary. Losartan potassium is a commonly prescribed high blood pressure medication that can help lower high blood pressure in hypertensive patients when used in conjunction with lifestyle changes. 

What Is Losartan Potassium?

Losartan potassium, also sold under the brand name Cozaar, is a blood pressure medication that belongs to a class of prescription drugs called angiotensin II receptor antagonists (ARBS) or angiotensin II receptor blockers. Losartan potassium was first approved for medical use in the United States by the Food and Drug Administration (FDA) in 1995 under the brand name Cozaar, and the generic form of the drug was released to the public in 2010 as an antihypertensive drug. The medication is available by prescription only.  

What Is Losartan Potassium Used to Treat and How Does it Work?

Our bodies contain a chemical called angiotensin II that causes the blood vessels to narrow and tighten. Angiotensin II receptor antagonists like losartan potassium block the action of angiotensin II, preventing it from being absorbed and helping to lower blood pressure by allowing the blood vessels to relax and open. Losartan potassium is primarily used to treat high blood pressure, but it also helps to prevent kidney problems caused by type 2 diabetes, known as diabetic nephropathy, in diabetic patients who also have high blood pressure. Patients with an enlarged heart or high blood pressure have a reduced risk of stroke and heart disease when taking losartan potassium.  

High Blood Pressure

We measure blood pressure as the force at which blood pushes against the walls of the blood vessels while the heart beats. When blood pressure is too high, it can cause damage to the blood vessels, but it’s also possible for your blood pressure to be too low. When blood pressure is too low, blood is unable to reach all of your organs and extremities and people may feel dizzy or lightheaded. Individuals are diagnosed with high blood pressure, also called hypertension, when the blood pushes too forcefully against the walls of the blood vessels consistently over an extended period of time. It’s normal for blood pressure to spike during exercise or stress, but the blood pressure should return to normal levels fairly quickly. 
High blood pressure is dangerous because it forces the heart and blood vessels to work at an increased effort level and with less efficiency when providing blood to the tissues and organs of the body. Hypertension, when left unmanaged, can cause microtears in the walls of the arteries that causes the blood vessels to narrow, further preventing blood from reaching different areas of the body and increasing blood pressure. About 95 percent of blood pressure cases have no obvious cause, such as medication use or an underlying health condition; doctors can only pinpoint the cause in about five percent of cases. All other cases are presumed to be caused by lifestyle factors and genetics. 

Diabetic Nephropathy

About 25 percent of people with diabetes will develop diabetic kidney disease, or diabetic nephropathy, over the course of their lifetime. Damage to the kidneys occurs when diabetes and high blood pressure impact the ability of the kidneys to remove waste products and extra fluid from the body. This condition, called diabetic nephropathy, can cause severe kidney disease or kidney failure, life-threatening conditions that require kidney dialysis or a kidney transplant.  Diabetic nephropathy is best managed by living a healthy lifestyle and carefully managing the treatment of diabetes and high blood pressure. 

What Are the Side Effects of Losartan Potassium?

Side effects associated with losartan potassium are categorized as either common or less common, and some may require medical attention. Common side effects associated with losartan potassium that usually do not need medical attention include:

  • Irritability
  • Ear congestion
  • Feeling sad or empty
  • Hearing loss
  • Increased sun sensitivity
  • Lack of appetite
  • Loss of sex drive
  • Body aches or back pain
  • Continuing ringing or buzzing in the ears
  • Constipation
  • The feeling of constant movement of self or surroundings
  • Headache, sometimes severe or throbbing
  • Inability to have or keep an erection
  • Redness or other skin discoloration
  • Severe sunburn
  • Sore throat
  • Trouble sleeping
  • Loss of voice
  • Sensation of spinning
  • Sneezing
  • Stuffy or runny nose
  • Trouble sleeping
  • Chills
  • Loss of interest or pleasure

As long as these common side effects are mild, they should go away within a few days or weeks. If side effects persist or allergic reactions occur, talk to your doctor.
Some side effects of losartan potassium do require medical attention. Check with your health care provider immediately if you experience any of the following serious adverse effects while taking losartan potassium:

  • Difficulty breathing
  • Dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • Fast heart rate, irregular heartbeat or chest pain
  • Blurred vision
  • Confusion
  • Weakness or heaviness of the legs
  • Burning, crawling, itching, numbness, prickling, tingling feelings, or “pins and needles”
  • Nervousness
  • Stomach pain
  • Unusual tiredness or weakness
  • Dizziness
  • Fainting
  • Nausea or vomiting
  • Numbness or tingling in the hands, feet, or lips
  • Sweating

What Are the Benefits of Losartan Potassium?

Losartan potassium has been effectively used to treat high blood pressure and reduce damage from diabetic nephropathy for over 25 years. Benefits of the medication include: 

  • When compared to other blood pressure medications, like atenolol, losartan potassium is more effective in reducing cardiovascular death, stroke, and myocardial infarction.
  • Patients with high blood pressure who take losartan potassium are less likely to experience new-onset diabetes than patients taking other blood pressure medications. 
  • Losartan potassium is available in a generic form and is highly affordable and accessible for most patients.

What Are the Risks of Taking Losartan Potassium?

Although there are many benefits associated with losartan potassium, as listed above, taking the medication also poses some risks. Always read the drug information before taking a medication. Risks associated with losartan potassium include:

  • Losartan potassium can interact with medications that contain aliskiren. Patients who have kidney disease or diabetes should not take losartan potassium with medications that contain aliskiren, such as Amturnide, Tekturna, Tekamlo, and Valturna to avoid problematic drug interactions.
  • Losartan potassium is not safe for pregnant and breastfeeding women due to the high risk of fetal injury and morbidity associated with the use of the drug during pregnancy. Women of childbearing age should use effective birth control when taking losartan potassium.
  • Patients should not use salt substitutes or potassium supplements to improve potassium levels while taking this medication. 
  • Patients should avoid all use of non-steroidal anti-inflammatory drugs and NSAIDs like naproxen and ibuprofen while taking this medication.
  • Patients with low blood pressure should use caution when taking this medication. 
  •  Dehydration may occur and can be dangerous, leading to low blood pressure. Patients should tell their doctors if they become sick, especially if they have vomiting or diarrhea that will not stop. 

How Do I Know What Dose of  Losartan Potassium I Should Take?

The dose of losartan potassium that your doctor prescribes will vary depending on the condition being treated, your age, overall health, and other medical conditions. Starting doses for both high blood pressure and diabetic nephropathy both begin at 50 mg taken orally once per day. A maintenance dose of 25 mg to 100 mg may be taken orally in 1 or 2 divided doses after the initial period ends. Overall, be sure to follow the medical advice of your doctor including informing them about any missed doses and storing the medication at room temperature. 

Can Women Who Are Pregnant or Breastfeeding Take Losartan Potassium?

Losartan potassium is not safe for pregnant women and may not be safe for breastfeeding women. Due to the high risk of fetal death and morbidity when used in the second and third trimester,  losartan potassium is considered highly dangerous for pregnant women and is categorized as pregnancy category D by the FDA for all trimesters, meaning that studies in pregnant women have shown that there is a risk to the fetus when taking losartan potassium. Mothers who are going to breast-feed should talk to their doctors if taking losartan potassium while breastfeeding, as conclusive research regarding risks medication transfer from breast milk to the infant has not been conducted. 

Who Should Not Take Losartan Potassium?

Losartan potassium is an effective drug for the treatment of high blood pressure and diabetic nephropathy, but it is not right for everyone. The following groups of people should not take losartan potassium:

  • People who are allergic to losartan potassium should not take the medication, nor should people taking medication that contains aliskiren (Amturnide, Tekturna, Tekamlo, Valturna). 
  • Patients with kidney disease, liver disease, congestive heart failure, electrolyte imbalances, or a history of dehydration should make sure to give their doctors a complete medical history prior to taking this medication.
  • Women who are pregnant, nursing, or planning to become pregnant should not take losartan potassium due to the risk of injury or death to the unborn baby associated with the medication. Women should use effective birth control while taking losartan potassium. 

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