Hydrochlorothiazide + Losartan is a prescription tablet that puts two blood pressure medicines into one: losartan potassium and hydrochlorothiazide. On some labels it is written as losartan potassium and hydrochlorothiazide. Losartan belongs to a group of medicines called angiotensin II receptor blockers (ARBs). Hydrochlorothiazide is a thiazide diuretic, often called a "water pill". Hydrochlorothiazide + Losartan is used to treat high blood pressure (hypertension). It is also used to lower the risk of stroke in people who have high blood pressure along with a thickened heart muscle. Bringing blood pressure down lowers the chance of strokes and heart attacks over time. The US reference product comes in three strengths of losartan/hydrochlorothiazide: 50 mg/12.5 mg, 100 mg/12.5 mg and 100 mg/25 mg.

High blood pressure often causes no symptoms, but over the years it can strain the heart and blood vessels and raise the risk of stroke and heart attack. Hydrochlorothiazide + Losartan lowers blood pressure in two different ways at the same time.

Losartan blocks the action of a natural hormone called angiotensin II. This hormone normally squeezes blood vessels narrower and tells the body to hold on to salt. When it is blocked, blood vessels stay more relaxed. Hydrochlorothiazide works on the kidneys, helping them pass out extra salt and water in the urine. With less fluid in the blood vessels, pressure falls. In studies, the blood pressure drop from the two medicines taken together was roughly the sum of what each one does on its own.

Hydrochlorothiazide + Losartan is used for two purposes. The first is treating high blood pressure. The second is lowering the risk of stroke in people with high blood pressure who also have left ventricular hypertrophy, which means the main pumping chamber of the heart has thickened. The product label notes evidence that this stroke benefit does not apply to Black patients.

Having both medicines in a single tablet, usually taken once a day, can make a daily routine simpler for people who need more than one medicine to control their blood pressure. It is usually not the first medicine prescribed for high blood pressure, unless blood pressure is high enough to need quick control. There is also a helpful pairing inside the tablet: hydrochlorothiazide can raise uric acid in the blood, and losartan tends to lower it, so the combination softens this effect.

Hydrochlorothiazide + Losartan needs regular medical follow-up. It carries a boxed warning, the strongest type of warning on a medicine label, because it can harm or cause the death of an unborn baby. It can also change potassium, sodium and other salt levels in the blood and can affect how the kidneys work, so your doctor may order blood tests from time to time. It is prescribed only after a doctor checks that it suits you.

Each tablet of Hydrochlorothiazide + Losartan contains two active ingredients:

• Losartan potassium: an angiotensin II receptor blocker (ARB).
• Hydrochlorothiazide: a thiazide diuretic (water pill).

The reference product is made in three strengths of losartan/hydrochlorothiazide: 50 mg/12.5 mg, 100 mg/12.5 mg and 100 mg/25 mg. Your prescription and pack will show which strength you have.

• High blood pressure (hypertension): Hydrochlorothiazide + Losartan is used to lower blood pressure, which reduces the risk of heart attacks and strokes.
• Lowering stroke risk in people with a thickened heart muscle: Hydrochlorothiazide + Losartan is used to reduce the risk of stroke in people who have high blood pressure together with left ventricular hypertrophy.

1. Two ways of lowering blood pressure in one tablet: Losartan relaxes blood vessels, and hydrochlorothiazide removes extra salt and water. Their effects on blood pressure add up.
2. Lower risk of heart attack and stroke: Controlling high blood pressure lowers the risk of heart attacks and strokes.
3. Stroke protection for people with a thickened heart: Hydrochlorothiazide + Losartan is used to reduce stroke risk in people with high blood pressure and left ventricular hypertrophy.
4. Once-a-day routine: The usual schedule is one tablet a day, which means fewer tablets to remember.
5. Softer effect on uric acid: Water pills like hydrochlorothiazide can raise uric acid, which is linked to gout. Losartan lowers uric acid, so the combination reduces this rise.

Most people take Hydrochlorothiazide + Losartan without major problems, but side effects can happen. Tell your doctor if any side effect bothers you or does not go away.

Common Side Effects (Usually Mild and may lessen with continued use)

• Dizziness or light-headedness, especially in the first few days
• Cold-like symptoms such as a blocked or runny nose and sore throat (upper respiratory infection)
• Back pain
• Passing urine more often than usual
• Headache
• Diarrhoea
• Loss of appetite
• Muscle cramps

Serious Side Effects (Seek Urgent Medical Attention)

• Angioedema: sudden swelling of the face, lips, tongue, throat, eyes, hands or feet, hoarseness, or trouble breathing or swallowing. Swelling of the throat can block the airway, so this is an emergency.
• Acute myopia and secondary angle-closure glaucoma: hydrochlorothiazide can, rarely, cause a sudden eye problem. Acute myopia means sudden short-sightedness (blurred distance vision). Angle-closure glaucoma is a sudden rise in pressure inside the eye that can damage sight permanently if it is not treated quickly. Watch for sudden blurred or reduced vision or eye pain, usually within hours to weeks of starting the medicine. People with a past allergy to sulfa (sulfonamide) medicines or penicillin may be at higher risk.
• Salt and fluid imbalance: very dry mouth, strong thirst, weakness, tiredness, drowsiness, restlessness, confusion, muscle pain or cramps, nausea, vomiting or a fast heartbeat. These can be signs of low potassium, low sodium or dehydration.
• High potassium (hyperkalaemia): losartan can raise potassium in the blood, which is why your doctor may check your blood salts.
• Kidney problems: passing much less urine than usual, or swelling. Medicines of this type can, rarely, cause acute kidney failure.
• Lupus flare-up: thiazide diuretics have been reported to trigger or worsen systemic lupus erythematosus (SLE), an immune condition that can cause joint pain, rash and tiredness.
• Rhabdomyolysis: a rare condition where muscle tissue breaks down. Watch for unexplained muscle pain, tenderness or weakness, especially with dark urine.
• Liver problems (hepatitis): yellowing of the skin or eyes, dark urine or pain in the upper right side of the tummy.
• Low platelets (thrombocytopenia): unusual bruising or bleeding.
• Severe allergic or skin reactions: hives, blisters, widespread red or peeling skin, or fever with rash.
• Non-melanoma skin cancer: hydrochlorothiazide is linked with a higher risk of non-melanoma skin cancer, such as basal cell and squamous cell skin cancer. The added risk is small but is higher with long-term use. Show your doctor any new or changing spot, lump or sore on your skin.
• Fainting or feeling very faint, especially when standing up.

• Take Hydrochlorothiazide + Losartan exactly as your doctor has prescribed. It is usually taken once a day.
• You can take it with or without food. Food slows how fast the tablet is absorbed but has only a small effect on how much medicine reaches your body. Try to keep the same habit each day, either always with a meal or always without.
• Take it at around the same time every day. Ask your doctor what timing suits you.
• Swallow the tablet with a glass of water.
• Keep taking Hydrochlorothiazide + Losartan even when you feel well. High blood pressure usually has no symptoms, and this medicine is usually needed long-term.
• Do not stop taking it or change the amount on your own. Speak to your doctor first.
• If you have been told to follow a low-salt diet, keep following it while on this medicine.

Hydrochlorothiazide + Losartan works through two separate pathways that both lead to lower blood pressure.

Losartan (angiotensin II receptor blocker): The body makes a hormone called angiotensin II. It attaches to "docking points" called AT1 receptors on blood vessel walls and in the adrenal glands. When it attaches, blood vessels tighten, and the adrenal glands release another hormone, aldosterone, which makes the body hold on to salt and water. Losartan sits on the AT1 receptors and blocks angiotensin II from attaching. Blood vessels stay relaxed, and less salt and water is held back. Both effects lower blood pressure. Much of the blood pressure lowering effect of losartan is seen within about one week, but the full effect can take 3 to 6 weeks.

Hydrochlorothiazide (thiazide diuretic): The kidneys filter blood and then take back much of the salt (sodium and chloride) they filter. Hydrochlorothiazide reduces how much salt the kidney tubes take back. More salt leaves the body in the urine, and water follows it. This reduces the amount of fluid in the blood vessels, which lowers pressure. The increase in urine usually starts within 2 hours of a tablet and is strongest at about 4 hours.

Why the two work well together: Because each medicine acts in a different way, their blood pressure lowering effects add together. Hydrochlorothiazide can lower potassium and raise uric acid, while losartan can raise potassium and lowers uric acid, which is one reason your doctor may still check your blood salts from time to time.

• Take Hydrochlorothiazide + Losartan at the same time every day with a glass of plain water.
• Stand up slowly, especially in the first few days. When getting out of bed, sit with your feet on the floor for a few minutes first.
• Do not use potassium tablets or potassium-based salt substitutes unless your doctor says it is fine.
• Stay out of strong sun where you can, and wear protective clothing and sunscreen, because hydrochlorothiazide raises the risk of non-melanoma skin cancer. Have your skin checked regularly.
• Drink enough fluids, especially in hot weather, and tell your doctor if you have vomiting or diarrhoea, as losing fluid can make your blood pressure drop too low.
• Keep up with blood tests your doctor orders to check potassium, sodium and kidney function.
• If you have diabetes, check your blood sugar as advised, since hydrochlorothiazide can change blood sugar control.
• If you have sudden blurred vision or eye pain, get medical help straight away.
• If you are planning a pregnancy, talk to your doctor before you try to conceive.

• Store at about 25°C (77°F). Short periods between 15°C and 30°C (59°F to 86°F) are acceptable.
• Keep the container tightly closed and protect the tablets from light.
• Keep away from excess heat and moisture, so avoid storing them in a bathroom.
• Keep the tablets in their original pack, out of the reach and sight of children and pets.

• Potassium-rich salt substitutes and potassium supplements: Losartan can raise potassium levels. Adding potassium-based salt substitutes or supplements can push potassium too high. Use them only if your doctor agrees.
• Grapefruit juice: The NHS advises avoiding grapefruit juice with losartan, as it can stop the medicine working properly.
• Liquorice: Liquorice contains glycyrrhizin, which can increase the loss of salts from the body, especially potassium, when combined with hydrochlorothiazide. Avoid large amounts of liquorice.
• Alcohol: Alcohol can add to the fall in blood pressure on standing and make dizziness worse.
• Salt: If your doctor has advised a low-salt diet, keep to it. It helps your blood pressure treatment work.
• Meals: Hydrochlorothiazide + Losartan can be taken with or without food. Food slows absorption slightly but does not meaningfully change how well it works.

Tell your doctor and pharmacist about all medicines, supplements and herbal products you take. Important interactions include:

• Aliskiren: Must not be combined with Hydrochlorothiazide + Losartan in people with diabetes. Combining it with ACE inhibitors (such as enalapril or ramipril), other ARBs or aliskiren raises the risk of low blood pressure, fainting, high potassium and kidney problems.
• Potassium supplements, potassium-sparing diuretics (such as spironolactone) and other medicines that raise potassium: Can lead to high potassium levels. Your doctor may check your potassium.
• Lithium (used for bipolar disorder): Both losartan and hydrochlorothiazide can raise lithium levels and cause lithium toxicity. Lithium levels need close checking.
• NSAID painkillers (such as ibuprofen, diclofenac and COX-2 inhibitors, a type of painkiller such as celecoxib or etoricoxib): In older people, people who are low on fluids, or people with kidney problems, these can worsen kidney function and may cause acute kidney failure. They can also reduce the blood pressure lowering effect.
• Diabetes medicines, including insulin: Hydrochlorothiazide can change blood sugar control, so the amount of your diabetes medicine may need adjusting.
• Cholestyramine and colestipol (cholesterol-lowering resins): These reduce how much hydrochlorothiazide is absorbed. The label advises taking hydrochlorothiazide at least 4 hours before or 4 to 6 hours after the resin.
• Corticosteroids (steroids) and ACTH (a hormone injection sometimes used in place of steroids): Can increase the loss of salts, especially potassium.
• Barbiturates (older sedative or seizure medicines such as phenobarbital) and narcotic (opioid) painkillers: Can add to dizziness and the fall in blood pressure on standing.
• Rifampicin and fluconazole: Rifampicin (an antibiotic used for tuberculosis) and fluconazole (an antifungal) can reduce the amount of active losartan in the body.
• Other blood pressure medicines: Can add to the blood pressure lowering effect. Your doctor will plan any combination.

• Pregnancy or planning pregnancy: Hydrochlorothiazide + Losartan can harm an unborn baby and should be stopped as soon as pregnancy is found.
• Inability to pass urine (anuria): Hydrochlorothiazide + Losartan must not be used.
• Diabetes: Must not be combined with aliskiren. Hydrochlorothiazide can also affect blood sugar control.
• Kidney disease: Kidney function can worsen, including acute kidney failure in some people. Regular checks are needed, and safety in severe kidney disease has not been proven.
• Narrowed kidney arteries (renal artery stenosis) or severe heart failure: People whose kidneys depend heavily on the body's blood pressure hormones have a higher risk of sudden kidney failure on this medicine. Tell your doctor if you have either condition.
• Liver disease: Starting treatment with this combination is not recommended.
• Dehydration or low salt levels: People who are low on fluid or salt, for example from vomiting, diarrhoea or high doses of water pills, can have a large drop in blood pressure. This needs to be corrected before starting.
• Low potassium, low sodium, low magnesium or high calcium: Hydrochlorothiazide can lower potassium, sodium and magnesium and raise calcium. Losartan can raise potassium. Blood salts need checking.
• Gout or high uric acid: Thiazide water pills can raise uric acid and may bring on gout.
• High cholesterol or triglycerides: Hydrochlorothiazide may raise these blood fats.
• Lupus (SLE): Thiazides can trigger or worsen lupus.
• Allergy to sulfa medicines or penicillin, or a history of allergy or asthma: Allergic reactions to hydrochlorothiazide are more likely in people with a history of allergy or bronchial asthma. A past sulfa or penicillin allergy is also a risk factor for the sudden eye problem described under side effects.
• Past angioedema or allergy to any ingredient: Tell your doctor, as people allergic to any part of the tablet must not take it.
• Skin cancer or high sun exposure: Hydrochlorothiazide raises the risk of non-melanoma skin cancer.

Your doctor decides the right strength for you based on your blood pressure, other conditions and blood test results. Always follow the prescribed amount.

• This combination is usually not the first medicine prescribed for high blood pressure. Doctors generally use it when one medicine alone has not controlled blood pressure, or when blood pressure is high enough to need quick control.
• According to the US product label for the reference brand, the usual starting amount for high blood pressure is one tablet of 50 mg losartan with 12.5 mg hydrochlorothiazide once daily.
• If needed, your doctor may raise the strength after about 3 weeks, up to a maximum of 100 mg losartan with 25 mg hydrochlorothiazide once daily.
• It is taken once in 24 hours.
• The label notes that this combination is not recommended for starting treatment in people with liver disease, and that its safety in severe kidney disease has not been proven.

Do not change the strength or how often you take it without speaking to your doctor.

Taking too much Hydrochlorothiazide + Losartan can be dangerous. Possible signs include:

• Severe dizziness or fainting from very low blood pressure
• A fast heartbeat, or sometimes a slow heartbeat
• Dehydration from passing too much urine
• Signs of low salt levels, such as weakness, confusion, muscle cramps and extreme thirst

If you or someone else has taken too much, get emergency medical help straight away, even if there are no symptoms yet. Take the medicine pack with you to the hospital. Losartan cannot be removed from the blood by dialysis, so hospital treatment is supportive.

• Take the missed tablet as soon as you remember.
• If it is almost time for your next tablet, skip the missed one and take the next one at the usual time.
• Never take two tablets at once to make up for a missed one.
• If you often forget, try setting a daily phone alarm or linking the tablet to a daily habit, such as breakfast.

Get medical help straight away if you notice:

• You are pregnant or think you might be pregnant
• Swelling of the face, lips, tongue or throat, hoarseness, or trouble breathing or swallowing
• Sudden blurred or reduced vision, or eye pain
• Fainting, or severe dizziness when you stand up
• Very dry mouth, strong thirst, confusion, severe weakness, muscle pain or cramps, or a fast or irregular heartbeat
• Passing much less urine than usual
• Unexplained muscle pain or weakness with dark urine
• Yellowing of the skin or eyes
• Unusual bruising or bleeding
• Blistering, peeling or widespread rash, or fever with rash
• New joint pain with rash and tiredness (possible lupus)
• A new or changing spot, lump or sore on your skin