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Losartan
Antihypertensive — Angiotensin Receptor Blocker (ARB)Nigerian brand names:CozaarLosacorLostatinRepace
Reviewed by the PMC Medical Team · Promise Medical Centre
Overview
Losartan is an angiotensin receptor blocker (ARB) used primarily to treat high blood pressure (hypertension) and to protect the kidneys in people with type 2 diabetes who also have high blood pressure. It works by blocking the action of a hormone called angiotensin II, which normally causes blood vessels to narrow. By blocking this hormone, losartan relaxes blood vessels and lowers blood pressure. It is commonly used as an alternative to ACE inhibitors (like lisinopril) in patients who develop a persistent dry cough on ACE inhibitors.
Uses
Losartan is used to:
- Treat high blood pressure (hypertension) in adults and children over 6 years
- Reduce the risk of stroke in people with hypertension and an enlarged heart (left ventricular hypertrophy)
- Protect the kidneys (nephroprotection) in people with type 2 diabetes and high blood pressure who have protein in the urine (diabetic nephropathy)
- Treat heart failure when ACE inhibitors are not tolerated
How to Use
Take losartan exactly as prescribed.
Dosage: Usually 25–100 mg once daily. Your doctor will adjust based on response.
- Can be taken with or without food
- Take at the same time each day
- Blood pressure lowering begins within 1 week but full effect may take 3–6 weeks
- Do not stop taking losartan without your doctor's advice, even if you feel well — blood pressure returns quickly
Blood pressure monitoring: Check your blood pressure regularly as advised by your doctor.
Side Effects
Common side effects:
- Dizziness, especially when standing up quickly (postural hypotension) — stand up slowly
- Upper respiratory infections and stuffy/runny nose (more common than with ACE inhibitors)
- Back pain
- Headache
- Fatigue
- Elevated potassium levels (hyperkalemia) — especially in people with kidney disease or taking potassium-sparing medicines
Unlike ACE inhibitors, losartan does NOT typically cause a dry cough.
Serious side effects (rare — seek medical help immediately):
- Angioedema: Sudden swelling of the face, lips, tongue, or throat — stop the medicine and get emergency care
- Severe drop in blood pressure
- Kidney function decline
- Severe high potassium (muscle weakness, irregular heartbeat)
Warnings & Precautions
Do not take losartan if you:
- Are pregnant — losartan can cause serious harm or death to the unborn baby. Inform your doctor immediately if you become pregnant
- Are breastfeeding
- Have diabetes AND are taking aliskiren (Rasilez) — this combination is contraindicated
- Are allergic to losartan or any ARB
Important warnings:
- Kidney function: Your doctor should monitor your kidney function (creatinine, eGFR) and electrolytes (especially potassium) regularly
- Potassium: Avoid potassium supplements, potassium-containing salt substitutes, or potassium-sparing diuretics unless prescribed — can cause dangerously high potassium
- Dehydration: During fever, diarrhoea, or vomiting, losartan may cause kidney problems — stay well hydrated and inform your doctor
- First dose: May cause a drop in blood pressure when first started, especially if you are already dehydrated or on diuretics
- Surgery: Tell your surgeon you take losartan before any planned operation
Drug Interactions
Important interactions:
- NSAIDs (ibuprofen, diclofenac, aspirin): Reduce blood pressure-lowering effect and increase risk of kidney damage — avoid regular combined use
- Potassium-sparing diuretics (spironolactone, amiloride): Dangerous increase in potassium levels
- Potassium supplements: Further raises potassium
- Lithium: Losartan increases lithium levels — monitor carefully
- Aliskiren: Contraindicated in diabetes — increases risk of low blood pressure, kidney failure, and high potassium
- ACE inhibitors (lisinopril, enalapril): Dual blockade increases risk of low blood pressure, kidney failure, and high potassium — generally avoid combination
- Rifampicin (used for TB): Reduces losartan effect
- Fluconazole: May increase losartan blood levels
Storage
Store below 30°C in a dry place, away from moisture and sunlight. Keep in original packaging. Keep out of reach of children.
Buy only NAFDAC-registered medications
Nigeria has a significant problem with counterfeit and substandard drugs. Always purchase medications from a licensed pharmacy and check the NAFDAC registration number on the package — verify at nafdac.gov.ng.