Reviewed on 3/29/2022

What Is Losartan / Hydrochlorothiazide and How Does It Work?

Losartan / Hydrochlorothiazide is a combination of prescription medication used for the treatment of high blood pressure and left ventricular hypertrophy related to high blood pressure.

  • Losartan / Hydrochlorothiazide is available under the following different brand names: Hyzaar

What Are Dosages of Losartan / Hydrochlorothiazide?

Adult dosage


  • 50mg/12.5mg
  • 100mg/12.5mg
  • 100mg/25mg


Adult dosage

  • Initial: 50 mg/12.5 mg orally once daily
  • If dose titrated upward, not to exceed final titration of 100 mg/25 mg orally once daily or 50 mg/12.5 mg orally every 12 hours
  • Decrease losartan to 25 mg orally once daily initially if volume-depleted

Hypertension with left ventricular hypertrophy

Adult dosage

  • Initial: 50 mg/12.5 mg orally once daily; may increase to 100 mg/12.5 mg orally once daily and subsequently to 100 mg/25 mg if necessary to control blood pressure

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Are Side Effects Associated with Using Losartan / Hydrochlorothiazide?

Common side effects of Losartan / Hydrochlorothiazideinclude:

Serious side effects of Losartan/hydrochlorothiazide include:

  • hives,
  • difficult breathing,
  • swelling of the face, lips, tongue, or throat,
  • a light-headed feeling, 
  • irregular heartbeats,
  • eye pain, vision problems;
  • kidney problems--little or no urination, rapid weight gain, swelling in your hands, feet, or ankles;
  • new or worsening symptoms of lupus--joint pain, and a skin rash on your cheeks or arms that worsens in sunlight, or
  • signs of an electrolyte imbalance--increased thirst or urination, confusion, vomiting, constipation, muscle pain, leg cramps, irregular heartbeats, numbness or tingling, severe weakness, loss of movement, feeling jittery or unsteady.

Rare side effects of Losartan/hydrochlorothiazide include:

  • none 
This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.


Salt and sodium are the same. See Answer

What Other Drugs Interact with Losartan / Hydrochlorothiazide?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Losartan / Hydrochlorothiazide has severe interactions with no other drugs.
  • Losartan / Hydrochlorothiazide has serious interactions with the following drugs:
  • Losartan / Hydrochlorothiazide has moderate interactions with at least 161 other drugs.
  • Losartan / Hydrochlorothiazide has minor interactions with at least 149 other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns.

What Are Warnings and Precautions for Losartan / Hydrochlorothiazide?


  • Hypersensitivity to losartan, hydrochlorothiazides, or sulfonamides
  • Anuria
  • Coadministration with aliskiren in patients with diabetes

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Losartan/hydrochlorothiazide?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Losartan/hydrochlorothiazide?”


  • In patients with the activated renin-angiotensin system, such as volume-or salt-depleted patients (e.g., those being treated with high doses of diuretics), symptomatic hypotension may occur after initiation of treatment; correct volume or salt depletion prior to administration; do not use drug combination as initial therapy in patients with intravascular volume depletion
  • Stroke risk reduction may be less effective in African-Americans
  • Intravascular volume or salt depletion should be corrected prior to use
  • Monitor serum lithium levels in patients receiving lithium and hydrochlorothiazide
  • Inform female patients of childbearing age about consequences of exposure to losartan during pregnancy and the importance of informing their physician about pregnancy while on therapy; discontinue if pregnancy detected
  • Monitor for signs of fluid or electrolyte imbalance, including hyponatremia, hypomagnesemia, hypochloremic alkalosis, and hypokalemia
  • Hydrochlorothiazide may alter glucose tolerance and raise serum levels of cholesterol and triglycerides
  • If oliguria or hypotension occurs in neonate with a history of in utero exposure, direct attention toward support of blood pressure and renal perfusion; exchange transfusions or dialysis may be required as a means of reversing hypotension and/or substituting for disordered renal function
  • Acute transient myopia and acute angle-closure glaucoma have been reported, particularly with a history of sulfonamide or penicillin allergy (hydrochlorothiazide is a sulfonamide)
  • Coadministration with corticosteroids, ACTH, or glycyrrhizin (found in licorice) may intensify electrolyte depletion, particularly hypokalemia
  • Monitor renal function and potassium in susceptible patients
  • Exacerbation of systemic lupus erythematosus reported
  • Dual blockade of the renin-angiotensin-aldosterone system (ie, ARB plus an ACE inhibitor) in patients with established atherosclerotic disease, heart failure, or with diabetes with end-organ damage is associated with a higher frequency of hypotension, syncope, hyperkalemia, and changes in renal function (including acute renal failure) as compared with the use of a single renin-angiotensin-aldosterone system agent; closely monitor blood pressure, renal function and electrolytes in patients on losartan and other agents that affect the renin-angiotensin system (RAS)
  • Hyperuricemia may occur or frank gout may be precipitated in patients receiving thiazide therapy; because losartan decreases uric acid, losartan in combination with hydrochlorothiazide attenuates diuretic-induced hyperuricemia
  • Hydrochlorothiazide decreases urinary calcium excretion and may cause elevations of serum calcium; monitor calcium levels
  • Concomitant use of other drugs that may increase serum potassium may lead to hyperkalemia
  • Photosensitivity reported; instruct patients to protect skin from the sun and undergo regular skin cancer screening

Pregnancy and Lactation

  • Therapy can cause fetal harm when administered to a pregnant woman; use of drugs that act on the renin-angiotensin system during second and third trimesters of pregnancy reduces fetal renal function and increases fetal and neonatal morbidity and death
  • Most epidemiologic studies examining fetal abnormalities after exposure to antihypertensive use in the first trimester have not distinguished drugs affecting the renin-angiotensin system from other antihypertensive agents; when pregnancy is detected, discontinue therapy as soon as possible
  • Hypertension in pregnancy increases the maternal risk for pre-eclampsia, gestational diabetes, premature delivery, and delivery complications (eg, need for cesarean section, postpartum hemorrhage)
  • Hypertension increases the fetal risk for intrauterine growth restriction and intrauterine death; pregnant women with hypertension should be carefully monitored and managed accordingly
  • Fetal/neonatal adverse reactions
    • Losartan
      • Use of drugs that act on the renin-angiotensin system in second and third trimesters of pregnancy can result in oligohydramnios, reduced fetal renal function leading to anuria and renal failure, fetal lung hypoplasia, skeletal deformations, including skull hypoplasia, hypotension, and death
      • In the unusual case that there is no appropriate alternative to therapy with drugs affecting the renin-angiotensin system for a particular patient, apprise the mother of the potential risk to the fetus
      • Perform serial ultrasound examinations to assess the intra-amniotic environment; if oligohydramnios is observed, discontinue therapy, unless it is considered lifesaving for the mother
      • Fetal testing may be appropriate, based on the week of gestation
      • Patients and physicians should be aware, however, that oligohydramnios may not appear until after the fetus has sustained an irreversible injury; closely observe neonates with histories of in utero exposure to drug combination for hypotension, oliguria, and hyperkalemia
      • In neonates with a history of in utero exposure to the drug combination, if oliguria or hypotension occurs, support blood pressure and renal perfusion
      • Exchange transfusions or dialysis may be required as a means of reversing hypotension and replacing the renal function
    • Hydrochlorothiazide
      • Thiazides can cross the placenta, and concentrations reached in the umbilical vein approach those in maternal plasma
      • Like other diuretics, the drug can cause placental hypoperfusion; it accumulates in amniotic fluid, with reported concentrations up to 19 times higher than in umbilical vein plasma
      • Use of thiazides during pregnancy is associated with a risk of fetal or neonatal jaundice or thrombocytopenia
      • Since they do not alter the course of preeclampsia, these drugs should not be used to treat hypertension in pregnant women
      • The use of hydrochlorothiazide for other indications in pregnancy should be avoided
  • Lactation
    • Not known whether losartan is excreted in human milk, but significant levels of losartan and its active metabolite were shown to be present in rat milk; thiazides appear in human milk; because of potential for adverse effects on the nursing infants, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account importance of the drug to mother
Medscape. Losartan/Hydrochlorothiazide.


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