Cozaar Side Effects

Generic Name: losartan

Note: This page contains information about the side effects of losartan. Some of the dosage forms included on this document may not apply to the brand name Cozaar.

Not all side effects for Cozaar may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to losartan: oral tablet

In addition to its needed effects, some unwanted effects may be caused by losartan (the active ingredient contained in Cozaar). In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking losartan:

More common
  • Abdominal or stomach pain
  • anxiety
  • bladder pain
  • bloody or cloudy urine
  • blurred vision
  • chills
  • cold sweats
  • coma
  • confusion
  • cool, pale skin
  • depression
  • difficult breathing
  • difficult, burning, or painful urination
  • dizziness
  • fast heartbeat
  • frequent urge to urinate
  • headache
  • increased hunger
  • irregular heartbeat
  • lower back or side pain
  • nausea or vomiting
  • nightmares
  • numbness or tingling in the hands, feet, or lips
  • pale skin
  • seizures
  • shakiness
  • shortness of breath
  • slurred speech
  • troubled breathing with exertion
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • weakness or heaviness of the legs
  • Arm, back, or jaw pain
  • chest pain or discomfort
  • chest tightness or heaviness
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • fainting
  • fast, irregular, pounding, or racing heartbeat or pulse
  • inability to speak
  • pain or discomfort in the arms, jaw, back, or neck
  • severe or sudden headache
  • sweating
  • swelling or puffiness of the face
  • temporary blindness
  • unsteadiness or awkwardness
  • weakness in the arm or leg on one side of the body, sudden and severe
  • weakness in the arms, hands, legs, or feet
Incidence not known
  • Black, tarry stools
  • bleeding gums
  • cough
  • dark urine
  • difficulty with swallowing
  • general tiredness and weakness
  • hives
  • itching
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • light-colored stools
  • muscle cramps or spasms
  • muscle pain or stiffness
  • pinpoint red spots on the skin
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • skin rash
  • upper right abdominal or stomach pain
  • yellow eyes and skin

Some of the side effects that can occur with losartan may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common
  • Blindness
  • body aches or pain
  • decreased vision
  • dry cough
  • ear congestion
  • loss of voice
  • nasal congestion
  • runny nose
  • sneezing
  • sore throat
Less common
  • Acid or sour stomach
  • back pain
  • belching
  • difficulty with moving
  • heartburn
  • increased sensitivity to pain
  • increased sensitivity to touch
  • indigestion
  • joint pain
  • lack or loss of strength
  • pain in the knees or legs
  • pain or tenderness around the eyes and cheekbones
  • stomach discomfort or upset
  • swollen joints
  • trouble sleeping
  • weight gain
  • Ankle, knee, or great toe joint pain
  • bloated
  • change or loss of taste
  • depression
  • difficulty having a bowel movement (stool)
  • dry skin
  • excess air or gas in the stomach or intestines
  • full feeling
  • hair loss or thinning of the hair
  • hearing loss
  • increased sensitivity of the skin to sunlight
  • loss of appetite
  • passing gas
  • redness or other discoloration of the skin
  • severe sunburn
  • weight loss

For Healthcare Professionals

Applies to losartan: oral tablet


Losartan is generally well tolerated. The overall incidence of adverse experiences reported with losartan (the active ingredient contained in Cozaar) appears to be similar to placebo. Discontinuation of therapy due to adverse drug events has been reported in 2.3% of patients receiving losartan and 3.7% of patients receiving placebo.

General side effects reported postmarketing have included malaise.

Nervous system

A single case of migraine headache has been associated with the use of losartan (the active ingredient contained in Cozaar) in a 50-year-old woman with hypertension and no history of migraine headaches or motion sickness. Her migraine headache resolved upon substitution with enalapril and recurred upon rechallenge with losartan.

Nervous system side effects have included headache (up to 14%), asthenia, fatigue, or dizziness (14%), and insomnia in 1% of patients. Single cases of reversible ageusia and migraine headache have been reported. Dysgeusia has been reported in postmarketing experience.


Cardiovascular side effects have included dizziness in 3.5% (compared with 2.1% on placebo) and rare reports of first-dose orthostatic hypotension. It has also been reported that losartan (the active ingredient contained in Cozaar) generated signals for cardiac failure, pulmonary edema and peripheral ischemia. Fingernail clubbing has also been associated with the use of losartan. In addition, angioneurotic edema has been reported.

A 52-year-old man with a history of focal segmental glomerulosclerosis, hypertension, proteinuria, and an allergy to radiographic contrast material, who was taking bisoprolol-HCTZ and terazosin (captopril had been discontinued due to cough), developed a "scratchy throat", facial flushing, and swelling of the lips and right face within 30 minutes after a single 50 mg dose of losartan. There were no signs or symptoms of pulmonary edema. The patient recovered after diphenhydramine therapy.


Respiratory side effects have included cough; however, in contrast to the ACE inhibitors, the incidence of cough associated with losartan (the active ingredient contained in Cozaar) (3.4%) is similar to placebo (3.3%). One comparative study has shown that losartan reduces cough in patients who have a history of cough associated with ACE inhibitors. However, cases of cough, including rechallenges, have been associated with losartan use in postmarketing research. Upper respiratory tract infection has been reported in 7.9% of treated patients, compared with 6.9% with placebo. Nasal congestion has been reported in 1% to 2% of patients. Laboratory preparation of losartan (after pulverizing tablets) by pharmacists has resulted in bronchospasm.

Angiotensin II receptor blockade, unlike ACE inhibition, has no impact on the processing of peptides such as bradykinin and substance P, two peptides able to induce cough.

Intradermal and spirometry testing of the pharmacists who experienced bronchospasm during preparation of losartan (double-blinded, placebo-controlled, crossover study) revealed reproducible symptoms associated with decreased FEV1 measurements. Because of the small sample size, the spirometry results did not reach statistical significance.


A 49-year-old hypertensive woman was switched from enalapril to losartan (the active ingredient contained in Cozaar) because of fatigue. One week after starting losartan, the patient reported a persistent metallic taste, a tickling cough, and intestinal symptoms. Symptoms disappeared after discontinuation of losartan.

A 69-year-old hypertensive woman was switched to losartan from perindopril due to a tickling cough. A burning feeling on the tongue and a complete loss of taste developed three months after starting losartan. Perindopril was reinstituted and the taste disturbances disappeared within one week.

A 39-year-old hypertensive male was changed from enalapril to losartan because of a persistent cough. After one week, the patient complained of nausea, vomiting, and epigastric pain. Elevated amylase and lipase levels were noted. Five days after losartan was discontinued, laboratory values returned to normal. Gastrointestinal symptoms and elevated pancreatic enzyme values returned when losartan was reinstituted at a lower dosage.

Gastrointestinal complaints have been reported in less than 3% of patients, and have included loose bowel movements, dyspepsia, epigastric discomfort, and nausea. Dysgeusia, ageusia, and oral ulcers have been rarely reported. Acute pancreatitis has been reported.


Musculoskeletal side effects have included reports of pain, typically back or leg pain, in approximately 1% of patients, compared with 0% with placebo. In addition, rare reports of rhabdomyolysis have been reported during postmarketing experience in patients receiving angiotensin II receptor blockers.


Renal side effects have rarely included new or worsened renal insufficiency or hyperkalemia associated with decreased renal function. The net effects of losartan (the active ingredient contained in Cozaar) and the ACE inhibitors on renal hemodynamics and kidney function are similar. Minor increases in blood urea nitrogen (BUN) or serum creatinine have been reported (less than 0.1%). In addition, acute renal failure associated with losartan therapy has been reported in at least one patient with bilateral renal artery stenosis.

Rare cases of acute renal failure, including acute oliguric renal failure, have been associated with the use of losartan in patients who are susceptible to reduced renal plasma flow (e.g., decreased cardiac output, renal artery stenosis, preexisting renal insufficiency). Losartan causes only minor decreases in plasma aldosterone.

The increase in plasma renin activity associated with losartan is relatively small compared with those increases associated with ACE inhibitors. These blunted increases do not appear to affect the antihypertensive response to the antagonist.

In one study of patients with significant proteinuria and moderate renal insufficiency (average creatinine clearance greater than 60 mL/min), losartan 50 to 100 mg/day was associated with significantly increased renal plasma flow and significantly decreased urinary excretion of total protein, albumin, and immunoglobulin.


Psychiatric side effects have included a single case of psychosis (reversible and reproducible on rechallenge of the drug) in an elderly woman with no personal or family history of mental illness or illicit drug use.

The pathogenesis of losartan-induced psychosis, if indeed it exists, is unknown. The author of this case report speculates that losartan may inhibit the enzyme enkephalinase, blocking the breakdown of the naturally-occurring opioid enkephalin. Opioids inhibit the release of substance P from primary sensory neurons. Perhaps, like ACE inhibitors, losartan might decrease plasma dopamine beta-hydroxylase concentrations.


Metabolic side effects have included uricosuric effects and decreased serum uric acid levels. Animal data have shown that losartan (the active ingredient contained in Cozaar) may inhibit uric acid reabsorption in the proximal renal tubule, which can result in uricosuria and a small human trial demonstrated uricosuric effects. Cases of uric acid calculi have not been associated with the use of losartan or other angiotensin II receptor antagonists. Hyperkalemia and hyponatremia have also been reported.


Dermatologic side effects have rarely been reported and include dermatitis, dry skin, ecchymosis, erythema, flushing, pruritus, rash, sweating, and urticaria. Losartan (the active ingredient contained in Cozaar) has been implicated in several case reports of de novo development or exacerbation of psoriasis. Erythroderma has been reported in postmarketing experience.


Hypersensitivity reactions have been reported including angioedema with swelling of the larynx and glottis causing airway obstruction and/or swelling of the face, lips, and pharynx, and/or tongue.


A 77-year-old hypertensive male was prescribed 50 mg losartan (the active ingredient contained in Cozaar) a day. The patient mistakenly took losartan 50 mg three times a day for six weeks. Laboratory tests showed elevated serum creatinine, BUN, total bilirubin, AST, ALT, and GGT. Normalization of the laboratory values occurred within one month of discontinuing losartan.

Hepatic side effects have included occasional reports of increases in hepatic enzymes and serum bilirubin. Less than 0.1% of patients from large-scale controlled trials discontinued therapy due to increased liver function tests. Hepatitis has been reported rarely.


Hematologic side effects have included reports of small decreases in hemoglobin and hematocrit. In addition, anemia has been reported in renal transplant recipients (not having post-transplant erythrocytosis) treated with losartan (the active ingredient contained in Cozaar) Losartan has also been implicated in a case of immune thrombocytopenia. Thrombocytopenia has been noted in postmarketing experience.


Immunologic side effects have included a case of Henoch-Schonlein purpura with a high titer of x-specific antineutrophil cytoplasmic antibodies (xANCA).

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