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All about: Losartan Potassium/Hydrochlorothiazide

Big Image Pronouncation: (low-SAHR-tan poe-TASS-ee-uhm/high-droe-klor-oh-THIGH-uh-zide)
Class: Antihypertensive combination

Trade Names:
- Tablets 12.5 mg hydrochlorothiazide/50 mg losartan potassium
- Tablets 12.5 mg hydrochlorothiazide/100 mg losartan potassium
- Tablets 25 mg hydrochlorothiazide/100 mg losartan potassium

Mechanism of Action


Losartan antagonizes the effect of angiotensin II (vasoconstriction and aldosterone secretion) by blocking the angiotensin II receptor (AT1 receptor) in vascular smooth muscle and the adrenal gland, producing decreased BP; hydrochlorothiazide inhibits reabsorption of sodium and chloride in ascending loop of Henle and early distal tubules.

Indications and Usage



Anuria; hypersensitivity to other sulfonamide-derivatives or any component of product.

Dosage and Administration


PO 50 mg losartan/12.5 mg hydrochlorothiazide once daily is usual dose (max, 100 mg losartan/25 mg hydrochlorothiazide daily).

General Advice

Administer once daily in the morning, with or without food. Administer with food if GI upset occurs.


Store tablets at controlled room temperature (59° to 86°F). Keep container tightly closed. Protect from light.

Drug Interactions

Losartan potassium Fluconazole

Losartan plasma levels may be elevated, increasing the antihypertensive and adverse effects.


Plasma levels of lithium may be elevated, increasing the pharmacologic and adverse effects.

Rifamycins (eg, rifampin)

Losartan plasma levels may be reduced, decreasing the antihypertensive effects.

Potassium-sparing diuretics (eg, spironolactone), potassium supplements, salt substitutes containing potassium

May lead to increased serum potassium.

Hydrochlorothiazide Alcohol, barbiturates, narcotics

Increased risk of orthostatic hypotension.

Antidiabetic agents

Dose adjustments of antidiabetic agent may be needed.


Actions of other antihypertensive agents may be potentiated.

Cholestyramine, colestipol resins

Absorption of hydrochlorothiazide may be impaired.

ACTH, corticosteroids

Increased risk of electrolyte depletion (eg, hypokalemia).

Pressor amines (eg, norepinephrine)

Decreased response to pressor amine.

Nondepolarizing skeletal muscle relaxants (eg, turbocurarine)

Responsiveness to muscle relaxant may be increased.


Plasma levels of lithium may be elevated, increasing the risk of toxicity.


Antihypertensive, diuretic, and natriuretic effects of hydrochlorothiazide may be reduced.

Laboratory Test Interactions

Serum levels of protein-bound iodine may be decreased without signs of thyroid dysfunction.

Adverse Reactions


Palpitations; orthostatic effects, angina pectoris, arrhythmias (eg, atrial fibrillation, sinus bradycardia, tachycardia, ventricular tachycardia, ventricular fibrillation), CVA, hypotension, MI, second-degree AV block (losartan); orthostatic hypotension (hydrochlorothiazide).


Dizziness; syncope, anxiety, ataxia, confusion, depression, dream abnormality, hyperesthesia, insomnia, decreased libido, memory impairment, migraine, nervousness, panic disorder, paresthesia, peripheral neuropathy, sleep disorder, somnolence, tremor, vertigo (losartan); restlessness (hydrochlorothiazide).


Rash; alopecia, dermatitis, dry skin, ecchymosis, erythema, flushing, photosensitivity, pruritus, sweating, urticaria (losartan); photosensitivity, urticaria, necrotizing angiitis (vasculitis and cutaneous vasculitis), erythema multiforme (eg, Stevens-Johnson syndrome), exfoliative dermatitis (eg, toxic epidermal necrolysis), purpura (hydrochlorothiazide).


Sinusitis; cough; nasal congestion, angioedema, pharyngeal discomfort, rhinitis, blurred vision, burning/stinging in the eyes, conjunctivitis, decreased visual acuity, taste perversion, tinnitus (losartan); transient blurred vision, xanthopsia (hydrochlorothiazide).


Abdominal pain; anorexia, constipation, dental pain, dry mouth, dyspepsia, flatulence, gastritis, vomiting (losartan); pancreatitis, sialadenitis, cramping, gastric irritation (hydrochlorothiazide).


Impotence, nocturia, urinary frequency, UTI (losartan); glucosuria, renal failure, renal dysfunction, interstitial nephritis (hydrochlorothiazide).


Anemia (losartan); aplastic anemia, agranulocytosis, leukopenia, hemolytic anemia, thrombocytopenia (hydrochlorothiazide).


Jaundice (intrahepatic cholestatic jaundice) (hydrochlorothiazide).


Edema; gout (losartan); hyperglycemia, hyperuricemia (hydrochlorothiazide).


Upper respiratory tract infection; dyspnea, epistaxis, respiratory congestion (losartan); respiratory distress (eg, pneumonitis, pulmonary edema) (hydrochlorothiazide).


Back pain; chest pain, facial edema, arm pain, arthralgia, arthritis, fibromyalgia, hip pain, joint swelling, knee pain, leg pain, muscle cramps, muscle weakness, musculoskeletal pain, myalgia, shoulder pain, stiffness (losartan); weakness, fever, muscle spasm (hydrochlorothiazide).



When used in pregnancy during the second and third trimesters, drugs that act directly on the renin-angiotensin system can cause injury and even death to the developing fetus. When pregnancy is detected, discontinue therapy as soon as possible.


Blood sugar

Monitor blood sugar in diabetic patient when drug is started or dose is changed.


Category C (first trimester); Category D (second and third trimester).


Undetermined (losartan); excreted in breast milk (hydrochlorothiazide).


Safety and efficacy not established.


May occur in patients with or without history of allergy or bronchial asthma; cross-sensitivity with sulfonamides may also occur.

Renal Function

Use with caution.

Hepatic Function

Do not use.

Hypotension, volume-depleted patients

Correct condition before using drug.

Systemic lupus erythematosus

Exacerbation or activation may occur with thiazide diuretics.



Hypotension, tachycardia, bradycardia, electrolyte depletion (eg, hypokalemia), dehydration.

Patient Information

  • Advise patient to take every day as prescribed, without regard to meals.
  • Advise patient to try to take at the same time each day.
  • Inform patient that drug controls, but not does cure, hypertension and to continue taking drug as prescribed even when BP is not elevated.
  • Caution patient not to change the dose or stop taking unless advised to do so by health care provider.
  • Instruct patient to continue taking other BP medications as prescribed by health care provider.
  • Instruct patient in BP and pulse measurement skills.
  • Advise patient to monitor and record BP and pulse at home and to inform health care provider should abnormal measurements be noted. Also advise patient to take record of BP and pulse to each follow-up visit.
  • Caution patient to avoid sudden position changes to prevent orthostatic hypotension.
  • Instruct patient to lie or sit down if they experience dizziness or lightheadedness when standing.
  • Caution patient that inadequate fluid intake, excessive perspiration, diarrhea, or vomiting can lead to excessive fall in BP resulting in lightheadedness or fainting.
  • Instruct diabetic patient to monitor blood glucose more frequently when drug is started or dose is changed and to inform health care provider of significant changes in readings.
  • Caution patient to avoid unnecessary exposure to UV light (eg, sunlight, tanning booths) and to use sunscreen and wear protective clothing when exposed to UV light to avoid photosensitivity reaction.
  • Emphasize to hypertensive patient importance of other modalities on BP: weight control, regular exercise, smoking cessation, and moderate intake of alcohol and salt.
  • Instruct patient to stop taking drug and immediately report any of the following symptoms to health care provider: fainting or swelling of the face, lips, eyelids or tongue.
  • Caution patient to not take any prescription or OTC medications, salt substitutes, or dietary supplements unless advised to do so by health care provider.

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