Losartan and Hydrochlorothiazide (Oral)

Also known in the US as Hyzaar, this drug combination of Losartan and hydrochlorothiazide is used in the treatment of high blood pressure and to lower the risk of stroke in those with heart disease.


Losartan and hydrochlorothiazide is a combination drug used alone or in combination with other medications in the treatment of high blood pressure. High blood pressure increases the work of the arteries and heart, thus overworking them. If it continues for a long period of time, the arteries and heart may not function correctly. This can damage the blood vessels of the heart, brain, and kidneys which could result in heart failure, a stroke, or kidney failure. If you lower your blood pressure, you can reduce your risk of suffering from heart attacks and strokes.

This drug combination is also used to reduce the risk of stroke in those patients who suffer from enlargement of the heart and high blood pressure.

Losartan is an angiotensin II receptor blocker and it works by blocking a substance contained in the body that forces the blood vessels to tighten. Losartan works by relaxing the blood vessels and consequently lowering the blood pressure. When the blood pressure is lower, the supply of oxygen and blood to the heart is increased.

Hydrochlorothiazide is a thiazide diuretic which works by reducing the amount of water contained in the body by increasing the flow of urine. This, in turn, helps to lower the overall blood pressure.

You can only obtain this medication via a doctors prescription and it is available in the dosage form of tablet for oral consumption.

Conditions treated

Type of medication

  • Oral tablet

Side effects

Alongside the intended effects of this drug, there are some side effects you may suffer from. Not all of these may be present, but if they are, you may need medical attention.

Inform your doctor immediately if you suffer from any of the following side effects whilst using this drug combination:


  • Tarry, black stools

Incidence not known

  • Dark-colored urine

Some of the side effects that may occur, don't typically require medical attention as they usually disappear as your body begins adjusting to the medication. You can, however, ask your healthcare professional for advice on ways to reduce or prevent these side effects. You should contact your doctor if any of the following side effects become bothersome or linger.

Less common

  • Flu or cold like symptoms


  • A dry cough

You may suffer from other side effects that are not listed above. You should contact your doctor if you have any other side effects that are bothersome.


The final dose of any medication will depend upon a number of different factors. This will include your weight, age, and height, any other medical conditions you suffer from or any other medications you are currently taking. The final dose will also depend on the strength of the medication, the duration you are taking the medication and your response to the first dose. The following doses are only guidelines. Do not change your dose without speaking to your doctor first. If you take too much of a medication you could increase your risk of side effects, or if you take too little, you could reduce your treatment.

For oral dosage form (tablets) for high blood pressure:

Adults: At first, one tablet once daily. Your doctor can also increase your dose as required. Typically, however, the dose is no more than 25 mg of hydrochlorothiazide and 100 mg of losartan each day.

Children: The final dose and use are determined by your doctor.

For lowering risk of stroke in patients with enlargement of the heart and high blood pressure:

Adults: At first, one tablet once daily. Your doctor can adjust your dose as necessary.

Children: The dose or use will be determined by your doctor.

Missed Dose

If you miss a dose of Losartan and Hydrochlorothiazide, then simply take it as soon as you have remembered. This is unless it's almost time for your next dose. In this case, you should skip the dose you have missed and return to your regular dosing schedule. Don't double your doses to make up for a missed dose of this medication.

Proper Use

In addition to this medication, you may be required to take treatment for your high blood pressure such as changes in the types of foods you eat, including weight control and especially foods high in sodium (salt). Your healthcare professional will tell you which of these is the most important for you. Before changing your diet, you should always check with your doctor.

Many people who have high blood pressure will not notice any signs of the problem. Most will actually feel normal. It's extremely important you take your medication as has been directed by your doctor and you visit your appointments with your doctor even if you are feeling well.

Remember that this medication cannot cure your high blood pressure but it can control it. You must always continue to take your medication as directed if you want it to lower your blood pressure and keep it low. You may have to take high blood pressure medication for the rest of your life. If high blood pressure isn't treated, it can cause serious problems such as blood vessel disease, heart failure, stroke, or kidney disease.

This medication may be taken with or without the consumption of food.

This medication comes alongside a patient information leaflet. You should read and follow the instructions carefully. Speak with your healthcare professional if you have any questions.

If you also use colestipol or cholestyramine, take these at least four hours after you take this medication.


Drug interactions can occur with this drug. To help avoid these, it's important that you give your healthcare team a full list of all the different medications you are taking. This should include all prescription and nonprescription drugs, vitamin supplements and herbal products. You should also make them aware of all the different medical conditions you suffer from too.

The use of this medication is not typically recommended with any of these medications. Your doctor may avoid treating you with this drug or change some of the other drugs you are taking.

  • Dofetilide

The use of this medication alongside any of the following is not typically recommended. However, in some cases, it may be required. If you are prescribed both medications together, your doctor may alter the frequency or dose of both medications.

  • Nepafenac

The use of this medication alongside any of the following medications can cause an increased risk of some side effects, however, the use of both drugs may be the best treatment plan for you. If you are given both medications together, your doctor may alter the dose or frequency in which you use either medication.

  • Fepradinol

Other Interactions

Some medications can't be used when eating or eating some types of food as it can increase your risk of interactions. The use of tobacco and alcohol can also increase your risk of interactions. You should discuss with your doctor about the use of this drug combination alongside alcohol, food or tobacco.

Other Medical Problems

The presence of other medical conditions can affect the use of this medication. Ensure you let your doctor know if you have any other medical conditions, especially:

  • Sympathectomy'Blood pressure'lowering effects of this medication could be increased.


Before you decide to take this medication, there are a number of precautions and warnings you need to consider first. Some of these are listed below and you should discuss these alongside your doctor to decide whether this medication is the best route for your treatment.


You should let your doctor know if you have ever suffered from an allergic reaction to this medication or other medications. You should also make them aware of any other allergies you may suffer from including to preservatives, animals, foods or dyes.

Pediatric population

Appropriate studies have not been conducted on the relationship of age to the effects of this drug combination in the younger population. Therefore efficacy and safety have not been established.

Geriatric population

Appropriate studies conducted to date have not indicated a geriatric-specific problem that could limit the effectiveness of this drug combination in the elderly population. However, older patients are more likely to suffer from the unwanted side effects of this medication, which could require a degree of caution in those patients who are receiving this drug combination.

Use in pregnancy and breastfeeding

This drug is under FDA pregnancy category D. Do not take this drug combination if you are pregnant. If you use this drug during pregnancy it can cause loss of the unborn child or cause birth defects. If you fall pregnant or intend on getting pregnant whilst taking this drug combination, you should call your doctor immediately.

It is unknown whether this drug can pass into breast milk. You should let your doctor know if you are currently breastfeeding and weigh up the positional risk and benefits together.

It's extremely important that your doctor monitors your progress at regular appointments to ensure that this medication is working correctly. Your doctor may take urine and blood tests to check for unwanted side effects.

Using this medication whilst you are pregnant can harm your unborn child. You should use an effective form of birth control to stop yourself from falling pregnant.

This medication can cause lightheadedness, dizziness, or fainting, especially when you get up suddenly from a sitting or lying position. Ensure you know how you react to this medication before you use machinery, drive, or do anything else that could be dangerous if you are feeling dizzy. If you do begin to feel dizzy, you should lie down so you don't faint. You should then sit for a few minutes before standing to prevent the dizziness from reoccurring.

Check with your doctor immediately if you become sick while taking this medication, especially if you have severe or continuing vomiting or nausea, or diarrhea that doesn't stop. These conditions can cause you to lose too much water and may lead to lower blood pressure. You can also lose water via sweating, so ensure you drink plenty of water in hot weather or during exercise.

Check with your doctor right away if you experience blurred vision, eye pain, difficulty reading, or any other changes in vision that occur during or after treatment. This can be a sign of serious eye issues. Your doctor may ask that you see an eye doctor.

This medication could affect the results of your blood sugar levels. Those who suffer from type 1 or type 2 diabetes may notice a change in the results of urine or blood tests. Speak with your doctor if you have any questions.

Speak with your doctor before you use any supplements, medicines, or salt substitutes that contain potassium.

If you take narcotic pain relievers, sleeping pills or drink alcohol with this medication, it can intensify a feeling of lightheadedness, dizziness, or feeling faint. You should tell your doctor if you are using sleeping pills or drinking alcohol, or using pain relievers.

Don't take other medications unless they have been discussed previously with your healthcare team. This especially includes prescription or nonprescription medications for asthma, appetite control, colds, hay fever, cough, or sinus problems.


Ensure this drug combination is stored out of the reach of children at room temperature. It should be kept away from heat, light, and moisture. Don't let this medication freeze. Dispose of any medication that has expired or you no longer need. You should ask your local pharmacist or healthcare professional for advice on the best method of disposal for this medication.


When used correctly, this drug combination is successful in the treatment of high blood pressure. However, due to a large number of interactions possible, it's important that your doctor or healthcare professional is aware of all medications you are currently taking, including other medical conditions you suffer from. The safety and efficacy of this drug have not been established in children. You should not use this drug whilst pregnant as to do so could produce birth defects or result in the death of the unborn child. Let your doctor know right away if you fall pregnant. Discuss the potential risks and benefits of using this drug whilst breastfeeding. Only take this medication as directed by your doctor and attend all appointments to monitor your progress. Let your doctor know if your condition is not improving, or it is getting worse. You need to use this medication regularly to obtain the greatest benefit from it. To ensure you remember to take your tablets, try taking them at the same time each day. You should continue to take this medication even if you don't "feel" sick. Most people who suffer from high blood pressure don't experience any illness. If you require any further information about the use of this drug combination or you have any other questions or queries, you should contact your doctor or a local healthcare professional for more advice.