Losartan

Medication angiotensin II receptor blocker heart & blood pressure

Aka: Cozaar, losartan potassium

Brands seen in Singapore: Cozaar, Angizaar, Lozarsin, Rosart, Myotan

Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.

How to use

What it’s for

Prescribed for high blood pressure and heart failure

When to take

NHS: usually once a day, at the SAMe time every day

Take with

Water · NHS: with or without food, but no grapefruit juice

Pros & cons

Pros

NHS: usually once a day, with or without food
HealthHub: blocks angiotensin ii at blood vessel walls
NHS: may also suit children aged 6 to 17

Cons

NHS: dizziness, tiredness, headache, oedema
HealthHub: potassium and kidney function get monitored
HealthHub: can injure a developing fetus in pregnancy

Sources

HSA — Listing of Registered Therapeutic Products (data.gov.sg open dataset, 5,511 rows, pulled in full via datastore_search and filtered locally) · read 2026-08-27
what it says
“All 35 registered losartan products (19 single-ingredient) carry Forensicclassification 'Prescription Only' — SIN08588P COZAAR TABLET 50 mg · SIN13720P Angizaar-50mg · SIN15076P LOZARSIN · SIN14314P ROSART · SIN14475P MYOTAN”
NHS Medicines A-Z — Losartan: what losartan is for · read 2026-08-27
what it says
“Losartan is a medicine used to treat high blood pressure and heart failure. It's only available on prescription … a type of medicine called an angiotensin receptor blocker (ARB).”
NHS Medicines A-Z — Losartan: how to take losartan · read 2026-08-27
what it says
“Most people need to take losartan once a day … take it at any time of day, but try to take it at the same time every day; take it with water, with or without food”
NHS Medicines A-Z — Losartan: side effects · read 2026-08-27
what it says
“Common side effects of losartan can include: dizziness; tiredness; headache; tummy pain; feeling sick (nausea) or being sick (vomiting); swelling in your legs, ankles or feet (oedema)”
NHS Medicines A-Z — Losartan: who can and cannot take it · read 2026-08-27
what it says
“Most adults aged 18 years or over can take losartan. Losartan may also be suitable for children aged 6 to 17 years old … not suitable if: … severe heart failure … problems with your liver … angioedema”
NHS Medicines A-Z — Losartan: taking it with other medicines · read 2026-08-27
what it says
“other medicines used to treat high blood pressure, including beta blockers and ACE inhibitors like lisinopril; … diuretics, such as spironolactone; supplements and salt substitutes … that contain potassium; some NSAIDs … lithium”
NHS Medicines A-Z — Losartan: food, drink and alcohol · read 2026-08-27
what it says
“avoid drinking grapefruit juice because it can stop your medicine working properly. Try to limit the amount of alcohol you drink while taking losartan because it can increase the risk of side effects.”
HealthHub (Pharmaceutical Society of Singapore) — Losartan: what is this medication for · read 2026-08-27
what it says
“Losartan lowers blood pressure by blocking the effects of a substance called Angiotensin II at the blood vessel walls. This medication can also be used for patients who have protein in their urine”
HealthHub — Losartan: precautions · read 2026-08-27
what it says
“Inform your doctor if you are pregnant or planning to get pregnant … Taking this medication can cause injury and death to your developing fetus. Your doctor may need to monitor your potassium levels and kidney function”
US FDA label for COZAAR (losartan potassium), section 2 Dosage and Administration, via openFDA drug/label.json (effective 2026-01-20) · read 2026-08-27
what it says
“The usual starting dose of COZAAR is 50 mg once daily. The dosage can be increased to a maximum dose of 100 mg once daily as needed to control blood pressure … A starting dose of 25 mg is recommended”

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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.

In Singapore

Classification
HSA register

prescription-only

This is the Singapore classification, taken from the HSA register. Dosing stays with the label and your pharmacist or doctor — this page never tells you how much to take.

What the label says

The US FDA label for cozaar states 'The usual starting dose of COZAAR is 50 mg once daily. The dosage can be increased to a maximum dose of 100 mg once daily as needed to control blood pressure' — 100 mg once daily is the adult label maximum; the SAMe label starts at 25 mg once daily in possible intravascular depletion and in mild-to-moderate hepatic impairment. SG-registered single-ingredient tablets are 50 mg and 100 mg. in Singapore the prescriber sets the dose.

Who should check first

Talk to a doctor or pharmacist before taking this if any of these apply to you.

Pregnancy: HealthHub: can injure and kill a developing fetus
Severe heart failure, or liver problems (NHS)
Past angioedema, or a reaction to another arb (NHS)
Vomiting, diarrhoea or fever: NHS: dehydration risk

Documented interactions

With medicines and supplements

Potassium supplements and salt substitutes: NHS lists supplements and salt substitutes that contain potassium among those that may not mix well⁶
NSAIDs including ibuprofen: NHS lists non-steroidal anti-inflammatory drugs among medicines that may not mix well with losartan⁶
Other blood pressure medicines and diuretics: NHS lists beta blockers, ace inhibitors such as lisinopril, and diuretics such as spironolactone⁶
Lithium: NHS lists lithium among medicines that may not mix well with losartan⁶

With food and drink

Grapefruit juice: NHS: it can stop the medicine working properly⁷

Only combinations someone has written down appear here. A pair that is missing is unrecorded, not cleared.