CoAprovel tablets contain two active ingredients, irbesartan and hydrochlorothiazide.


Pharmacist - M.B.A. (Public Health) D.I.C.


What is it used for? High blood pressure with…

Garvan J. Lynch
MBA (Public Health)

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What is it used for?

  • High blood pressure with no known cause (essential hypertension).

How does it work?

  • CoAprovel tablets contain two active ingredients, irbesartan and hydrochlorothiazide.
  • Hydrochlorothiazide is a type of medicine known as a thiazide diuretic. Thiazide diuretics act in the kidneys, where they increase the production of urine. They work by causing the kidneys to increase the amount of salts, such as potassium and sodium, that are filtered out of the blood and into the urine. When these salts are filtered out of the blood by the kidneys, water is also drawn alongside. As hydrochlorothiazide increases the removal of salts from the blood, it also causes more water to be drawn out of the blood and into the urine.
  • Removing water from the blood decreases the volume of fluid circulating through the blood vessels, which decreases the pressure within the blood vessels. Hydrochlorothiazide therefore lowers blood pressure.
  • Irbesartan is a type of medicine called an angiotensin II receptor antagonist. It works by preventing the action of a hormone in the body called angiotensin II.
  • Angiotensin II normally acts on special receptors in the body, with two main results. Firstly, it causes the peripheral blood vessels to narrow, and secondly, it stimulates the production of another hormone called aldosterone. Aldosterone causes salt and water to be retained by the kidneys, which increases the volume of fluid in the blood vessels.
  • Irbesartan blocks the receptors that angiotensin II acts on, and so prevents its actions. The main result of this is that the peripheral blood vessels are allowed to widen, which means that there is more space and less resistance in these blood vessels. This lowers the pressure inside the blood vessels.
  • Blocking the actions of angiotensin II also reduces the action of aldosterone on the kidneys. The result of this is an increase in the amount of fluid removed from the blood by the kidneys. This decreases the amount of fluid in the blood vessels, which also lessens the resistance and pressure in the blood vessels.
  • Irbesartan and hydrochlorothiazide have an additive effect on lowering blood pressure. They are used to treat high blood pressure in people whose blood pressure is not adequately controlled on one of the medicines alone.

Use with caution in

  • Decreased kidney function
  • Narrowing of the artery which supplies blood to the kidneys (renal artery stenosis)
  • Decreased liver function
  • Liver disease
  • Heart disease caused by inadequate blood flow to the heart (ischaemic heart disease)
  • Heart disease characterised by thickening of the internal heart muscle and a blockage inside the heart (hypertrophic obstructive cardiomyopathy)
  • Heart failure
  • Narrowing of one of the valves in the heart (mitral valve stenosis)
  • Narrowing of the main artery of the body (aortic stenosis)
  • Diabetes
  • Gout
  • History of allergies
  • History of asthma
  • Long-term inflammation of skin and some internal organs (systemic lupus erythematosus)
  • People with low fluid volume or salt levels in the body, eg due to diuretic therapy, low-sodium diet, diarrhoea or vomiting.

Not to be used in

  • Allergy to medicines from the sulphonamide group, eg the antibiotic sulfamethoxazole
  • Moderate to severely decreased kidney function
  • Severely decreased liver function
  • Liver damage due to disorder of the bile duct (biliary cirrhosis)
  • Failure of the normal flow of bile from the liver to the intestines (cholestasis)
  • High levels of calcium in the blood (hypercalcaemia)
  • Low potassium blood levels that cannot be corrected (refractory hypokalaemia)
  • Pregnancy
  • Breastfeeding
  • Rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption (CoAprovel tablets contain lactose).

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • This medicine should not be used in pregnancy, particularly in the second and third trimesters, as it may affect the growth and development of the foetus or have adverse effects on foetal tissues. Seek medical advice from your doctor.
  • This medicine may pass into breast milk and may also reduce the production of breast milk. It should not be used by breastfeeding mothers. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

  • Dizziness
  • Fatigue
  • Nausea and vomiting
  • Headache
  • Diarrhoea
  • A drop in blood pressure that occurs when going from lying down to sitting or standing, which results in dizziness and lightheadedness (postural hypotension)
  • Fainting
  • Increased heart rate (tachycardia)
  • High blood glucose level (hyperglycaemia)
  • Flushing
  • Weakness or loss of strength (asthenia)
  • Disturbances in the levels of chemical components (electrolytes) in the blood
  • Sexual problems
  • Sensation of ringing, or other noise in the ears (tinnitus)
  • Pain in the muscles and joints
  • Liver or kidney disorders
  • Blood disorders
  • Severe swelling of lips, face or tongue (angioedema)

The side effects listed above may not include all of the side effects reported by the drug's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

This medicine may enhance the effect of other medicines to treat high blood pressure. In particular, people taking diuretic medicines, eg furosemide, may have a large drop in blood pressure with the first dose. Since this may cause dizziness or fainting, if you are taking a diuretic medicine your doctor may reduce its dose or ask you to stop taking it two to three days before starting this medicine. This is to prevent your blood pressure from dropping too low.

Irbesartan and hydrochlorothiazide may increase the blood level of the medicine lithium, and this medicine is therefore not recommended for people taking lithium. If your doctor feels the combination is necessary, your lithium level should be closely monitored.

Irbesartan may increase blood potassium levels, therefore if this medicine is taken with other medicines that can increase blood potassium, this effect may be enhanced. These medicines include the following:

  • ciclosporin
  • potassium-sparing diuretics (eg spironolactone, triamterene, amiloride)
  • potassium supplements
  • potassium salts, eg potassium citrate
  • potassium-containing salt substitutes, eg Lo-salt
  • heparin.

Hydrochlorothiazide can decrease blood potassium levels, therefore if this medicine is taken with other medicines that can lower blood potassium, this effect may be enhanced. These medicines include the following:

  • other diuretics
  • amphotericin
  • carbenoxolone
  • corticosteroids
  • beta agonist bronchodilators such as salbutamol.

If you are taking any of these medicines that could affect your potassium level, your potassium level should be monitored. This is particularly important if you are taking digoxin or a medicine for abnormal heart beats.

Non-steroidal anti-inflammatory drugs (NSAIDs, eg indometacin) may reduce the blood pressure lowering effect of this medicine. They may also increase the risk of raised blood potassium and kidney problems when used in combination with this medicine. NSAIDs should be used with caution in people taking this medicine, particularly elderly people, and your doctor may want to monitor your kidney function.

Hydrochlorothiazide may raise blood glucose levels. People with diabetes should therefore carefully monitor their blood sugar while taking this medicine, as the effectiveness of antidiabetic medicines may be reduced. This effect may be enhanced if diazoxide or beta-blockers are also being taken. Dose adjustments of the antidiabetic medicine may be required. Discuss this with your doctor.

Hydrochlorothiazide may also raise uric acid levels. People with gout may therefore need adjustments to the doses of their gout medicines to keep them effective.

This medicine should not be taken within four hours of colestipol or colestyramine, as if they are taken at the same time they may reduce the absorption of hydrochlorothiazide from the gut.

Hydrochlorothiazide can increase blood calcium levels. Therefore if calcium or vitamin D supplements are taken with this medicine, blood calcium levels should be monitored.


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