Losartan Potassium; Uses, Dosage, Side Effects, Interactions, Pregnancy

Losartan
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Losartan is an angiotensin-receptor blocker (ARB) that may be used alone or with other agents to treat hypertension. Losartan and its longer acting metabolite, E-3174, lower blood pressure by antagonizing the renin-angiotensin-aldosterone system (RAAS); they compete with angiotensin II for binding to the type-1 angiotensin II receptor (AT1) subtype and prevents the blood pressure increasing effects of angiotensin II.It works by relaxing blood vessels so that blood can flow more easily. Unlike angiotensin-converting enzyme (ACE) inhibitors, ARBs do not have the adverse effect of dry cough.

Mechanism of Action of Losartan

Losartan competitively inhibits the binding of angiotensin II to AT1 in many tissues including vascular smooth muscle and the adrenal glands. Losartan is metabolized to its active metabolite, E-3174, which is 10 to 40 times more potent than losartan and acts as a non-competitive AT1 antagonist. Inhibition of angiotensin II binding to AT1 inhibits its AT1-mediated vasoconstrictive and aldosterone-secreting effects and results in decreased vascular resistance and blood pressure. Losartan is 1,000 times more selective for AT1 than AT2. Inhibition of aldosterone secretion may increase sodium and water excretion while decreasing potassium excretion. Losartan is effective for reducing blood pressure and may be used to treat essential hypertension, left ventricular hypertrophy and diabetic nephropathy.

Or

Angiotensin II (formed from angiotensin I in a reaction catalyzed by angiotensin converting enzyme (ACE, kininase II)), is a potent vasoconstrictor, the primary vasoactive hormone of the renin-angiotensin system and an important component in the pathophysiology of hypertension. It also stimulates aldosterone secretion by the adrenal cortex. Losartan and its principal active metabolite block the vasoconstrictor and aldosterone-secreting effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT1 receptor found in many tissues, (e.g., vascular smooth muscle, adrenal gland). There is also an AT2 receptor found in many tissues but it is not known to be associated with cardiovascular homeostasis. Both losartan and its principal active metabolite do not exhibit any partial agonist activity at the AT1 receptor and have much greater affinity (about 1000-fold) for the AT1 receptor than for the AT2 receptor. In vitro binding studies indicate that losartan is a reversible, competitive inhibitor of the AT1 receptor. The active metabolite is 10 to 40 times more potent by weight than losartan and appears to be a reversible, non-competitive inhibitor of the AT1 receptor. Neither losartan nor its active metabolite inhibits ACE (kininase II, the enzyme that converts angiotensin I to angiotensin II and degrades bradykinin); nor do they bind to or block other hormone receptors or ion channels known to be important in cardiovascular regulation.

Indications of Losartan

Therapeutic Indications of Losartan

  • Angiotensin II Type 1 Receptor Blockers; Anti-Arrhythmia Agents; Antihypertensive Agents
  • Losartan is indicated for the treatment of hypertension. It may be used alone or in combination with other antihypertensive agents, including diuretics.
  • Losartanis indicated to reduce the risk of stroke in patients with hypertension and left ventricular hypertrophy, but there is evidence that this benefit does not apply to Black patients
  • Losartan is indicated for the treatment of diabetic nephropathy with an elevated serum creatinine and proteinuria (urinary albumin to creatinine ratio =300 mg/g) in patients with type 2 diabetes and a history of hypertension. In this population,
  • Losartan reduces the rate of progression of nephropathy as measured by the occurrence of doubling of serum creatinine or end stage renal disease (need for dialysis or renal transplantation)
  • Angiotensin II receptor antagonists including losartan have been used in the management of congestive heart failure

Contra indications of Losartan

  • Extreme loss of body water
  • High amount of potassium in the blood
  • Renal artery stenosis
  • Abnormally low blood pressure
  • Liver problems
  • Blockage of a bile duct
  • Kidney disease with reduction in kidney function
  • Pregnancy
  • Decreased Blood Volume
  • Second and third trimester of pregnancy
  • Biliary obstructive disorders.
  • Severe hepatic impairment.
  • Hypersensitivity to the active substance or to any of the excipients
  • Pregnancy
  • Decreased blood volume
  • Allergies to losartan & ARB-Angiotensin Receptor Antagonist

Dosage of Losartan

Strengths: 25 mg, 50 mg, 100 mg

The typical starting dosage is 50 mg once daily. Dosages range between 25 and 100 mg per day. You take losartan once or twice per day.

Hypertension

  • Initial dose: 50 mg orally once a day
  • Maximum dose: 100 mg orally once a day

Diabetic Nephropathy

  • Initial dose: 50 mg orally once a day
  • Maximum dose: 100 mg orally once a day

Pediatric Dose for Hypertension

6 Years or Older

  • Initial dose: 0.7 mg/kg orally once a day (up to 50 mg total)

Side Effects of Losartan

The most common

Common

Rare

Drug Interactions of Losartan

Losartan may interact with following drugs, supplements, & may change the efficacy of drugs

Pregnancy & Lactation of Losartan

FDA Pregnancy Category D

Pregnancy

Losartan should not be taken by pregnant women as it can cause harm to an unborn child. If you are planning to become pregnant, discuss alternative medications for blood pressure control with your doctor. If you become pregnant while taking this medication, stop taking it and tell your doctor at once.

Lactation

It is not known if losartan passes into breast milk. If the breastfeeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding. The safety and effectiveness of using this medication have not been established for children less than 6 years of age.

References

 

Losartan

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