Hydrochlorothiazide / losartan Side Effects

Not all side effects for hydrochlorothiazide / losartan 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 hydrochlorothiazide / losartan: oral tablet

In addition to its needed effects, some unwanted effects may be caused by hydrochlorothiazide / losartan. 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 hydrochlorothiazide / losartan:

Symptoms of fluid and electrolyte imbalance
  • Dry mouth
  • increased thirst
  • muscle cramps or pain
  • nausea or vomiting
  • unusual tiredness or weakness
  • weak or irregular heartbeat
  • Black, tarry stools
  • blood in the urine or stools
  • cough or hoarseness accompanied by chills or fever, lower back or side pain, or painful or difficult urination
  • fainting
  • pinpoint red spots on the skin
  • pounding heartbeat
  • severe stomach pain, nausea, and vomiting
  • skin rash
  • swelling of the feet or lower legs
  • unusual bleeding or bruising
Incidence not known
  • Coma
  • confusion
  • convulsions
  • dark-colored urine
  • decreased urine output
  • fast or irregular heartbeat
  • fever
  • irritability
  • large, flat, blue, or purplish patches in the skin
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • light-colored stools
  • muscle spasms
  • muscle stiffness
  • muscle twitching
  • painful knees and ankles
  • raised red swellings on the skin, the buttocks, legs or ankles
  • restlessness
  • seizures
  • shortness of breath
  • swelling of the face, ankles, or hands
  • upper right abdominal or stomach pain
  • weakness
  • yellow eyes and skin

Some of the side effects that can occur with hydrochlorothiazide / 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:

Less common
  • Cold or flu-like symptoms
  • dizziness
  • headache
  • increased sensitivity of the skin to sunlight
  • sore throat
  • stomach pain
  • Dry cough
  • sinus problems

For Healthcare Professionals

Applies to hydrochlorothiazide / losartan: oral tablet


Hydrochlorothiazide-losartan is generally well-tolerated. The overall incidence of adverse experiences reported with losartan monotherapy appears to be similar to placebo. For the most part, side effects associated with the combination drug are transient and mild. In controlled clinical trials, discontinuation of therapy due to adverse drug events has been reported in 2.5% and 2.3% of patients treated with the combination and placebo, respectively.

General side effects reported postmarketing have included malaise thought to be related to the losartan component.


Since HCTZ may increase total serum cholesterol by 11%, LDL lipoprotein cholesterol by 12%, and VLDL lipoprotein cholesterol levels by 50%, and since it may reduce insulin secretion, it should be used with caution in patients with hypercholesterolemia and/or diabetes.

HCTZ-induced hyperuricemia may be an important consideration in patients with a history of gout. Hypophosphatemia and low serum magnesium concentrations may occur, but are usually clinically insignificant except in malnourished patients.

Metabolic side effects associated with HCTZ are more commonly associated with daily HCTZ doses of 50 mg or more, which are not recommended with the combination product. These side effects may occur at lower doses, however, and include mild hypokalemia (decrease of 0.5 mEq/L), metabolic alkalosis, hyponatremia, hypomagnesemia, hypercalcemia, hyperglycemia, hypercholesterolemia and elevated serum uric acid levels.


Hypersensitivity reactions typically present as nausea, vomiting, diarrhea, and rash, and are probably due to the HCTZ component. Hypersensitivity is reported in less than 1% of patients. Cases of acute pulmonary edema, interstitial cystitis or nephritis, and anaphylaxis have also been associated with HCTZ.


Cardiovascular side effects associated with losartan include dizziness in 5.7% (vs. 2.9% in placebo-treated subjects) and orthostatic hypotension. Rarely, HCTZ-induced hypokalemia or hyponatremia have been associated with significant cardiac arrhythmias including ventricular ectopy and complete AV heart block. Hypokalemia is much less likely with the combination drug, however, since losartan inhibits aldosterone secretion. Fingernail clubbing has also been associated with the use of losartan. In addition, angioneurotic edema has been reported during losartan therapy.

Nervous system

Nervous system side effects associated with losartan include headache in up to 14%, asthenia/fatigue in 4%, insomnia in 1% of patients, and rare cases of ageusia (altered tasted) and migraine headache. Rare cases of cerebrovascular insufficiency have been associated with HCTZ induced plasma volume contraction. Dysgeusia has been reported with losartan in postmarketing experience.


A 67-year-old white woman with hypothyroidism, hypercalcemia, depression, and hypertension developed facial erythema, headaches, tremors, confusion, and personality changes associated with a new positive ANA and anti-nRNP and a skin biopsy consistent with lupus erythematosus while taking HCTZ, levothyroxine, and amitriptyline. The eruption resolved upon discontinuation of HCTZ, but she later developed a higher ANA titer associated with symptomatic diffuse interstitial pulmonary infiltrates. She was successfully treated with corticosteroids.

Dermatologic reactions associated with HCTZ include erythema annular centrifugum, acute eczematous dermatitis, and morbilliform or leukocytoclastic vasculitis. Thiazides may induce phototoxic dermatitis. In addition, a rare, distinct entity with clinical and laboratory features indistinguishable from those of subacute cutaneous lupus erythematosus has been associated with HCTZ. Erythroderma has been reported with losartan in postmarketing experience.


Renal side effects including new or worsened renal insufficiency may occur due to HCTZ-induced intravascular volume depletion. Rare cases of interstitial nephritis have been associated with HCTZ. Decreased renal function or hyperkalemia has only rarely been associated with losartan, although experience with this drug is limited compared with the related compounds, the ACE inhibitors. The effects of losartan and ACE inhibitors on renal hemodynamics and kidney function are similar. In addition, acute renal failure associated with losartan therapy has been reported in at least one patient with bilateral renal artery stenosis.

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 > 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.

Although HCTZ has been used to treat nephrogenic diabetes insipidus, a case in which the drug was believed to have caused this condition has been reported.


Gastrointestinal complaints have been reported in less than 2% of patients, and have included loose bowel movements, dyspepsia, epigastric discomfort, and nausea. Rare cases of pancreatitis and acute cholecystitis have been associated with HCTZ. Dysgeusia, ageusia, and oral ulcers associated with losartan therapy have been rarely reported. Acute pancreatitis has also been associated with losartan use.

Thiazide diuretics may increase serum cholesterol and triglycerides, resulting in increased risk of cholesterol gallstone formation. Reports of bowel strictures associated with thiazide ingestion were reported in the 1960's, although these patients were on a combination HCTZ-potassium product.


Respiratory system side effects are rare. Cough has been reported in 3.4% of treated patients and 3.3% of patients taking placebo. One comparative study has shown that losartan reduces coughing in patients who have a history of cough associated with ACE inhibitors. However, cases of cough, including rechallenge, have been associated with losartan use in postmarketing research. Nasal congestion has been reported in 1% to 2% of patients. Approximately 30 cases of acute noncardiogenic pulmonary edema have been associated with thiazide diuretics. These cases have been thought to be due to idiosyncrasy or a hypersensitivity mechanism.


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


Immunologic side effects are rare, and include cases of allergic vasculitis and hemolytic anemia associated with HCTZ. A case of Henoch-Schonlein purpura with a high titer of x-specific antineutrophil cytoplasmic antibodies (xANCA) has been associated with losartan therapy.


Hematologic side effects are rare. Cases of immune-complex hemolytic anemia, aplastic anemia, and thrombocytopenia have been associated with HCTZ. Hematologic side effects associated with losartan have included reports of small decreases in hemoglobin and hematocrit in which no patients were discontinued due to anemia. In addition, anemia has been reported in renal transplant recipients (not having posttransplant erythrocytosis) treated with losartan. Losartan has also been implicated in a case of immune thrombocytopenia. Thrombocytopenia has also been noted in postmarketing experience with losartan.


A prospective study of 34 patients who received oral thiazide diuretics for 14 years without interruption revealed an increased mean fasting blood glucose level after treatment. Withdrawal of thiazide therapy for 7 months in 10 of the patients resulted in mean reductions of 10% in the average fasting blood glucose value and 25% in the average 2-hour glucose tolerance test value. A control group was not reported.

Endocrinologic problems associated with thiazide diuretics include glucose intolerance and a potentially deleterious effect on the lipid profile. This may be important in some patients with or who are at risk for diabetes or coronary artery disease.


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


Ocular side effects have included idiosyncratic reactions to the hydrochlorothiazide component resulting in acute transient myopia and acute angle-closure glaucoma.

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