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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.[Ref]

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.[Ref]

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.[Ref]


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.[Ref]

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.[Ref]


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.[Ref]

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.[Ref]


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.[Ref]

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.[Ref]


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.[Ref]


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.[Ref]

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.[Ref]


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.[Ref]

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.[Ref]


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.[Ref]


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.[Ref]


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.[Ref]


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.[Ref]

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.[Ref]


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.[Ref]


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


1. F-D-C Reports, Inc. "Merck Cozaar antihypertensive approved april 14: labeling appears to suport Merck's claim of clean side-effect profile for first angiotensin II inhibitor." F-D-C Reports -- "The Pink Sheet" 57 (1995): 22

2. Oparil S, Barr E, Elkins M, Liss C, Vrecenak A, Edelman J "Efficacy, tolerability, and effects on quality of life of losartan, alone or with hydrochlorothiazide, versus amlodipine, alone or with hydrochlorothiazide, in patients with essential hypertension." Clin Ther 18 (1996): 608-25

3. Pitt B, Segal R, Martinez FA, et al. "Randomised trial of losartan versus captopril in patients over 65 with heart failure (Evaluation of Losartan in the Elderly Study, ELITE)." Lancet 349 (1997): 747-52

4. Goldberg MR, Tanaka W, Barchowsky A, Bradstreet TE, McCrea J, Lo MW, McWilliams EJ Jr, Bjornsson TD "Effects of losartan on blood pressure, plasma renin activity, and angiotensin II in volunteers." Hypertension 21 (1993): 704-13

5. Weir MR, Elkins M, Liss C, Vrecenak AJ, Barr E, Edelman JM "Efficacy, tolerability, and quality of life of losartan, alone or with hydrochlorothiazide, versus nifedipine GITS in patients with essential hypertension." Clin Ther 18 (1996): 411-28

6. Weber MA, Bryyny RL, Pratt JH, et al. "Blood pressure effects of the angiotensin II receptor blocker, losartan." Arch Intern Med 155 (1995): 405-11

7. Waeber B, Burnier M, Nussberger J, Brunner HR "Experience with angiotensin II antagonists in hypertensive patients." Clin Exp Pharmacol Physiol 23 ( Suppl (1996): s142-6

8. Goldberg AI, Dunlay MC, Sweet CS "Safety and tolerability of losartan potassium, and angiotensin II receptor antagonist, compared with hydrochlorothiazide, atenolol, felodipine ER, and angiotensin-converting enzyme inhibitors for the treatment of systemic hypertension." Am J Cardiol 75 (1995): 793-5

9. "Product Information. Cozaar (losartan)." Merck & Co, Inc, West Point, PA.

10. Byyny RL "Losartan potassium lowers blood pressure measured by ambulatory blood pressure monitoring." J Hypertens 13 Suppl (1995): s29-33

11. Ahmad S "Losartan and severe migraine." JAMA 274 (1995): 1266-7

12. Waeber B, Brunner HR "Angiotensin II antagonists: a new class of antihypertensive agent." Br J Clin Pract 50 (1996): 265-8

13. Schaefer KL, Porter JA "Angiotensin II receptor antagonists: the prototype losartan." Ann Pharmacother 30 (1996): 625-36

14. Mallion JM, Bradstreet DC, Makris L, Goldberg AI, Halasz S, Sweet CS, Lim NY, Madonna O "Antihypertensive efficacy and tolerability of once daily losartan potassium compared with captopril in patients with mild to moderate essential hypertension." J Hypertens 13 Suppl (1995): s35-41

15. Dahlof B, Keller SE, Makris L, Goldberg AI, Sweet CS, Lim NY "Efficacy and tolerability of losartan potassium and atenolol in patients with mild to moderate essential hypertension." Am J Hypertens 8 (1995): 578-83

16. Schlienger RG, Saxer M, Haefeli WE "Reversible ageusia associated with losartan." Lancet 347 (1996): 471-2

17. Gradman AH, Arcuri KE, Goldberg AI, Ikeda LS, Nelson EB, Snavely DB, Sweet CS "A randomized, placebo-controlled, double-blind, parallel study of various doses of losartan potassium compared with enalapril maleate in patients with essential hypertension." Hypertension 25 (1995): 1345-50

18. Goldberg AI, Dunlay MC, Sweet CS "Safety and tolerability of losartan compared with atenolol, felodipine and angiotensin converting enzyme inhibitors." J Hypertens 13 Suppl (1995): s77-80

19. "WHO system finds 13 drugs with AEs not in PDR, Martindale." F-D-C Reports -- "The Pink Sheet" 60 (1998): 16

20. Rush JE, Rajfer SI "Theoretical basis for the use of angiotensin II antagonists in the treatment of heart failure." J Hypertens 11 Suppl 3 (1993): s69-71

21. Warner KK, Visconti JA, Tschampel MM "Angiotensin II receptor blockers in patients with ACE inhibitor-induced angioedema." Ann Pharmacother 34 (2000): 526-8

22. Crozier I, Ikram H, Awan N, Cleland J, Stephen N, Dickstein K, Frey M, Young J, Klinger G, Makris L, et al "Losartan in heart failure. Hemodynamic effects and tolerability. Losartan Hemodynamic Study Group." Circulation 91 (1995): 691-7

23. Dickstein K, Gottlieb S, Fleck E, Kostis J, Levine B, DeKock M, LeJemtel T "Hemodynamic and neurohumoral effects of the angiotensin II antagonist losartan in patients with heart failure." J Hypertens Suppl 12 (1994): s31-5

24. Goldberg MR, Bradstreet TE, McWilliams EJ, Tanaka WK, Lipert S, Bjornsson TD, Waldman SA, Osborne B, Pivadori L, Lewis G, et al "Biochemical effects of losartan, a nonpeptide angiotensin II receptor antagonist, on the renin-angiotensin-aldosterone system in hypertensive patients." Hypertension 25 (1995): 37-46

25. Acker CG, Greenberg A "Angioedema induced by the angiotensin II blocker losartan." N Engl J Med 333 (1995): 1572

26. Dickstein K, Chang P, Willenheimer R, Haunso S, Remes J, Hall C, Kjekshus J "Comparison of the effects of losartan and enalapril on clinical status and exercise performance in patients with moderate or severe chronic heart failure." J Am Coll Cardiol 26 (1995): 438-45

27. Tikkanen I, Omvik P, Jensen HA "Comparison of the angiotensin II antagonist losartan with the angiotensin converting enzyme inhibitor enalapril in patients with essential hypertension." J Hypertens 13 (1995): 1343-51

28. Doig JK, MacFadyen RJ, Sweet CS, Lees KR, Reid JL "Dose-ranging study of the angiotensin type I receptor antagonist losartan (DuP753/MK954), in salt-deplete normal man." J Cardiovasc Pharmacol 21 (1993): 732-8

29. Packard KA, Arouni AJ, Hilleman DE, Gannon JM "Fingernail clubbing and chromonychia associated with the use of angiotensin II receptor blockers." Pharmacotherapy 24 (2004): 546-50

30. Dicpinigaitis PV, Thomas SA, Sherman MB, Gayle YE, Rosenstreich DL "Losartan-induced bronchospasm." J Allergy Clin Immunol 98 (1996): 1128-30

31. Ramsay LE, Yeo WW "Double-blind comparison of losartan, lisinopril and hydrochlorothiazide in hypertensive patients with a previous angiotensin converting enzyme inhibitor-associated cough." J Hypertens 13 Suppl (1995): s73-6

32. Karlberg BE "Cough and inhibition of the renin-angiotensin system." J Hypertens 11 Suppl 3 (1993): s49-52

33. Bosch X "Losartan-induced acute pancreatitis." Ann Intern Med 127 (1997): 1043-4

34. Fisher AA, Bassett ML "Acute Pancreatitis Associated with Angiotensin II Receptor Antagonists." Ann Pharmacother 36 (2002): 1883-6

35. Goffin E, Pochet JM, Lejuste P, DePlaen JF "Aphtous ulcers of the mouth associated with losartan." Clin Nephrol 50 (1998): 197

36. Tsuruoka S, Wakaumi M, Araki N, Ioka T, Sugimoto K, Fujimura A "Comparative study of taste disturbance by losartan and perindopril in healthy volunteers." J Clin Pharmacol 45 (2005): 1319-23

37. Heeringa M, van Puijenbroek EP "Reversible dysgeusia attributed to losartan." Ann Intern Med 129 (1998): 72

38. Tsunoda K, Abe K, Hagino T, Omata K, Misawa S, Imai Y, Yoshinaga K "Hypotensive effect of losartan, a nonpeptide angiotensin II receptor antagonist, in essential hypertension [published erratum appears in Am J Hypertens 1993 May;6(5 Pt 1):451]." Am J Hypertens 6 (1993): 28-32

39. Lee HY, Kim CH "Acute oliguric renal failure associated with angiotensin II receptor antagonists." Am J Med 111 (2001): 162-3

40. Cohen LS, Friedman EA "Losartan-induced azotemia in a diabetic recipient of a kidney transplant." N Engl J Med 334 (1996): 1271-2

41. Weber MA, Byyny RL, Pratt JH, Faison EP, Snavely DB, Goldberg AI, Nelson EB "Blood pressure effects of the angiotensin II receptor blocker, losartan." Arch Intern Med 155 (1995): 405-11

42. Ardaillou R, Chansel D "Glomerular effects of angiotensin II: a reappraisal based on studies with non-peptide receptor antagonists." J Hypertens 11 Suppl 3 (1993): s43-7

43. Wargo KA, Chong K, Chan EC "Acute renal failure secondary to angiotensin II receptor blockade in a patient with bilateral renal artery stenosis." Pharmacotherapy 23 (2003): 1199-204

44. Ostermann M, Goldsmith DJA, Doyle T, Kingswood JC, Sharpstone P "Reversible acute renal failure induced by losartan in a renal transplant recipient." Postgrad Med J 73 (1997): 105-7

45. Saine DR, Ahrens ER "Renal impairment associated with losartan." Ann Intern Med 124 (1996): 775

46. Gansevoort RT, de Zeeuw D, Shahinfar S, Redfield A, de Jong PE "Effects of the angiotensin II antagonist losartan in hypertensive patients with renal disease." J Hypertens Suppl 12 (1994): s37-42

47. Ahmad S "Losartan and reversible psychosis." Cardiology 87 (1996): 569-70

48. Wurzner G, Gerster JC, Chiolero A, et al. "Comparative effects of losartan and irbesartan on serum uric acid in hypertensive patients with hyperuricaemia and gout." J Hypertens 19 (2001): 1855-60

49. Yamamoto T, Moriwaki Y, Takahashi S, Tsutsumi Z, Hada T "Effect of losartan potassium, an angiotensin II receptor antagonist, on renal excretion of oxypurinol and purine bases." J Rheumatol 27 (2000): 2232-6

50. Marquart-Elbaz C, Grosshans E, Lipsker D, Lipsker D "Sartans, angiotensin II receptor antagonists, can induce psoriasis." Br J Dermatol 147 (2002): 617-8

51. Haddad AM "Possible losartan-induced rash." Am J Health Syst Pharm 54 (1997): 1333-4

52. Chu YJ, Pearson VE "Angioedema due to losartan." Ann Pharmacother 33 (1999): 936-8

53. Rivera JO "Losartan-induced angioedema." Ann Pharmacother 33 (1999): 933-5

54. Rupprecht R, Vente C, Grafe A, Fuchs T "Angioedema due to losartan." Allergy 54 (1999): 81-2

55. Andrade RJ "Hepatic injury associated with losartan." Ann Pharmacother 32 (1998): 1371

56. Ersoy A, Kahvecioglu S, Ersoy C, Cift A, Dilek K "Anemia due to losartan in hypertensive renal transplant recipients without posttransplant erythrocytosis." Transplant Proc 37 (2005): 2148-50

57. Celik A, Ok E, Unsal A, Toz H, Atabay G "Comparison of enalapril and losartan in the treatment of posttransplant erythrocytosis." Nephron 86 (2000): 394-5

58. Ada S, Yalamanchili M, Friedenberg W "Immune Thrombocytopenia after Losartan Therapy." Ann Intern Med 137 (2002): 704

59. Brouard M, Piguet V, Chavaz P, Borradori L "Schonlein-Henoch purpura associated with losartan treatment and presence of antineutrophil cytoplasmic antibodies of x specificity." Br J Dermatol 145 (2001): 362-3

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