Losartan: Uses, Dosage, Side Effects, and More
1. Drug Name
Generic Name: Losartan
Brand Name(s):
- Pakistan: Cozaar, Losacar
- India: Cozaar, Losacar
- United States: Cozaar
- United Kingdom: Cozaar
2. Pharmacological Class
Class: Angiotensin II Receptor Blocker (ARB)
Subclass: AT1 receptor antagonist
3. Mechanism of Action
Losartan selectively blocks the binding of angiotensin II to AT1 receptors in vascular smooth muscle and adrenal gland, preventing vasoconstriction and aldosterone secretion.
4. Indications
Primary Indications:
- Hypertension (high blood pressure)
- Reduction of stroke risk in patients with left ventricular hypertrophy
- Diabetic nephropathy with proteinuria
Off-label Uses:
- Heart failure
- Prevention of migraine headaches
- Alport syndrome
5. Dosage and Administration
Standard Dosage:
- Hypertension: Initial dose of 50 mg once daily; usual maintenance dose of 25-100 mg once daily.
- Reduction of stroke risk in patients with left ventricular hypertrophy: Initial dose of 50 mg once daily; usual maintenance dose of 50-100 mg once daily.
- Diabetic nephropathy: Initial dose of 50 mg once daily; usual maintenance dose of 50-100 mg once daily.
Route of Administration: Oral (tablets).
Special Populations:
- Pediatric: Safety and efficacy not established in children.
- Geriatric: No dosage adjustment necessary, but monitor for hypotension.
6. Pharmacokinetics
Absorption: Rapidly absorbed from the gastrointestinal tract.
Distribution: Crosses the placenta and is found in breast milk.
Metabolism: Minimal metabolism by cytochrome P450 enzymes.
Excretion: Primarily excreted in urine (35%) and feces (60%).
Half-life: 2 hours (active metabolite: 6-9 hours).
7. Contraindications
Losartan is contraindicated in patients with a history of hypersensitivity to losartan or any other component of the product. It should also not be used in pregnancy.
8. Warnings and Precautions
Use with caution in patients with renal impairment or hepatic impairment. Avoid use in patients with bilateral renal artery stenosis.
Avoid in pregnancy and advise females of reproductive potential to use effective contraception during therapy.
9. Side Effects
Common Side Effects: Dizziness, hypotension, hyperkalemia.
Serious Side Effects: Angioedema, renal impairment, hepatic impairment. Discontinue use and notify a healthcare provider immediately if these occur.
10. Drug Interactions
Major Interactions: Potassium-sparing diuretics, NSAIDs, and lithium may increase the risk of hyperkalemia.
Moderate Interactions: Antidiabetic agents, digoxin, and rifampin.
Minor Interactions: Cimetidine, grapefruit juice, and fluconazole.
11. Pregnancy and Lactation
Pregnancy Category: Category D - Avoid use during pregnancy, especially during the second and third trimesters, due to potential fetal harm.
Breastfeeding Considerations: Losartan is excreted in breast milk. Discontinue nursing or the drug, taking into account the importance of the drug to the mother.
12. Patient Counseling Information
Key Points for Patients:
- Take losartan exactly as prescribed. Do not skip doses or stop taking the medication without consulting your healthcare provider.
- Avoid potassium supplements and potassium-containing salt substitutes unless directed by your healthcare provider.
- Monitor your blood pressure regularly.
Administration Tips:
- Take losartan with or without food.
- Do not crush, chew, or break tablets; swallow them whole.
- If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not double dose to catch up.