Losartan was introduced under the brand name Cozaar in 1995 for the treatment of high blood pressure. At the time, it was the first of a new category of blood pressure medicines now known as ARBs, or angiotensin II receptor blockers. Although they work on the renin-angiotensin enzymes just as ACE inhibitors do, ARBs have some distinct differences from ACE inhibitors like lisinopril. Losartan side effects are not the same as those found with lisinopril or other ACE inhibitors.
Losartan is prescribed for high blood pressure, alone or in combination with other drugs. It is often prescribed as a fixed combination with hydrochlorothiazide (HCTZ). Originally, this combination pill carried the brand name Hyzaar, but both losartan and the losartan-HCTZ combination pills have been available in generic versions for a number of years. It appears that losartan may be less effective for African-American patients than for others (American Journal of Hypertension, Nov., 2003).
Losartan Side Effects:
Some of the most common side effects that people on losartan have experienced include dizziness, nasal stuffiness, diarrhea, muscle cramps or pains including back pain, fatigue and indigestion. People with diabetes may experience episodes of low blood sugar.
Other Losartan Side Effects:
- Low blood pressure
- Chest pain
- Nasal congestion, sinusitis, upper respiratory infection
- High potassium levels
- Angioedema (a reaction in which the throat or face may swell, possibly leading to a medical emergency)
- Anaphylaxis (a life-threatening allergic reaction in which the person has difficulty breathing)
- Fainting: this may be worsened by dehydration due to excessive sweating, diarrhea or vomiting
- Kidney injury
- Muscle breakdown
- Fetal toxicity if the mother is taking losartan
- Cough-less common than with ACE inhibitors, but persistent cough is occasionally a problem
Any symptoms should be reported to the doctor promptly.
Although dry eyes are not included in lists of losartan side effects, one reader reported severe dry eyes while taking this drug.
Use During Pregnancy:
Losartan, like other ARB medications, is not appropriate during the second or third trimesters of pregnancy. If a woman taking losartan becomes pregnant, she should consult her doctor as soon as possible. Nursing women should not take this drug without first discussing potential risks and benefits with their physician.
Interactions with Losartan:
Although losartan may be given in combination with many other types of blood pressure medicine, it should NOT be taken together with aliskiren (Tekturna) by people with diabetes or reduced renal function. This combination may lead to elevated potassium in the body (World Journal of Nephrology, Nov. 6, 2013). It could also put undue strain on the kidneys.
ARBs such as losartan work on the same enzyme system, generally, as the ACE (angiotensin-converting enzyme) inhibitors such as benazepril (Lotensin), captopril (Capoten), enalapril (Vasotec), lisinopril (Prinivil, Zestril), moexipril (Univasc), perindopril (Aceon), quinapril (Accupril), ramipril (Altace) and trandolapril (Mavik). Combining losartan with any of these does not improve effectiveness, but it does increase the probability of side effects.
Because losartan can increase the amount of potassium circulating in the bloodstream, it can be dangerous in combination with potassium-sparing diuretics such as amiloride (Midamor), spironolactone (Aldactone) or triamterene (Dyrenium, or as a component of HCTZ/triamterene = Dyazide or Maxzide). Combining such medications could lead to elevated potassium levels. For the same reason, salt substitutes containing potassium chloride (NoSalt, Lite Salt, etc.) should not be used without medical supervision.
People taking lithium to treat bipolar disorder may need to have the dose adjusted. Taking losartan at the same time can raise blood levels of lithium and make side effects more likely.
Certain medicines may interact with losartan to lower blood pressure too much or unexpectedly. They include a number of drugs used to treat serious psychiatric disorders:
- aripiprazole (Abilify)
- aripiprazole lauroxil (Aristada)
- asenapine (Saphris)
- brexpiprazole (Rexulti)
There are also a number of antihypertensives that may lower blood pressure too much if they are taken with losartan. These combinations should be avoided or the dosage of one or both drugs may require adjustment. These include:
- bendroflumethiazide
- bumetanide
- chlorothiazide
- chlorthalidone
- ethacrynic acid
- furosemide
- hydrochlorothiazide
- indapamide
- methyclothiazide
- metolazone
- torsemide
In addition, doctors need to be monitoring carefully if a person taking losartan is also taking an NSAID such as celecoxib, diclofenac, etodolac, ibuprofen, indomethacin, meloxicam, nabumetone, naproxen and others. These drugs may decrease the power of losartan to control blood pressure.
Losartan is metabolized by CYP enzymes in the liver (2C9 and 3A4). Despite this, it does not seem to have a significant interaction with grapefruit juice, which inhibits CYP3A4. Presumably that is because CYP 2C9 is more important for the metabolism of losartan.
The list of drug interactions here is not exhaustive, so be sure to check with your doctor and pharmacist to make sure that losartan is safe in combination with any other drugs you take.
Special Precautions:
People with liver disease may have trouble metabolizing losartan. The dose should be adjusted accordingly.
In people with severe congestive heart failure, losartan may put too much strain on the kidneys. The prescribing physician should be monitoring closely to make sure this is not happening.
Women should not take losartan if they are pregnant or nursing.
Taking Losartan:
Losartan may be taken when it is convenient, with or without food. It is taken once or twice a day, according to the prescription. The usual dose starts at 50 mg a day and may go to a maximum of 100 mg/day. People with reduced liver function and those taking a diuretic blood pressure medicine already are usually prescribed a lower dose of 25 mg daily to reduce the likelihood of losartan side effects.
Most recent revision: December 28, 2015
