Omesar plus tablets contain two active ingredients, olmesartan and hydrochlorothiazide. Olmesartan is a type of medicine called an angiotensin II receptor antagonist. Hydrochlorothiazide is a type of medicine called a thiazide diuretic. These are both medicines used to lower high blood pressure.
What is it used for?
- High blood pressure with no known cause (essential hypertension).
How does it work?
- Olmesartan 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. It causes the peripheral blood vessels to narrow, and it also 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.
- Olmesartan 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 helps lower blood pressure.
- Diuretics such as hydrochlorothiazide are sometimes referred to as ‘water tablets’.
Use with caution in
- Elderly people.
- People with low fluid volume or salt levels in the body, eg due to diuretic therapy, low-sodium diet, diarrhoea or vomiting.
- Kidney disease.
- Narrowing of the arteries that supply blood to the kidneys (renal artery stenosis).
- Narrowing of the arteries in the heart or brain (atherosclerosis).
- Narrowing of the main artery that leaves the heart to supply blood to the body (aortic stenosis).
- Narrowing of one of the valves in the heart (mitral valve stenosis).
- Heart disease characterised by thickening of the internal heart muscle and a blockage inside the heart (hypertrophic obstructive cardiomyopathy).
- Severe heart failure.
- Long-term inflammation of skin and some internal organs (systemic lupus erythematosus).
- History of allergies.
- History of asthma.
Pregnancy and breastfeeding
- This medicine should not be used in pregnancy, particularly in the second and third trimesters, as it may be harmful to the unborn baby. Seek further medical advice from your doctor. If you get pregnant while taking this medicine, stop taking it and consult your doctor immediately.
- It is not known if olmesartan passes into breast milk, however hydrochlorothiazide does pass into breast milk. It may also decrease the production of breast milk. This medicine should therefore not be used during breastfeeding. Mothers will need to either stop breastfeeding while taking this medicine, or not take this medicine. This will depend on how important the medicine is for treating the mother’s blood pressure. It is important to seek medical advice from your doctor.
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.
- Feeling faint.
- Low blood pressure (hypotension).
- Feeling of weakness (asthenia).
- Changes in potassium levels in the blood.
- Increased level of calcium in the blood.
- Increased level of uric acid in the blood (hyperuricaemia).
- Increased levels of triglycerides in the blood (hypertriglyceridaemia).
The side effects listed above may not include all of the side effects reported by the drug's manufacturer.
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 will have an additive effect with other medicines that decrease blood pressure, particularly other medicines used to treat high blood pressure (antihypertensives).
In people taking antihypertensive medicines it may cause a large drop in blood pressure with the first dose or after any dose increases, particularly in people taking diuretic medicines such as furosemide. This may cause dizziness, which can usually be relieved by lying down until the symptoms pass. If you frequently feel dizzy while taking this medicine in combination with other blood pressure lowering medicines you should let your doctor know, as your doses may need adjusting.
Other medicines that decrease blood pressure include the following:
- alpha-blockers such as prazosin (these are also used to treat an enlarged prostate gland)
- beta-blockers such as propranolol
- calcium-channel blockers such as verapamil, nifedipine
- diuretics, eg furosemide, bendroflumethiazide
- nitrates, eg glyceryl trinitrate
- certain antidepressants
- certain antipsychotics
- benzodiazepines, eg temazepam.
There may be a risk of raised potassium levels in the blood (hyperkalaemia) if any of the following medicines are taken with olmesartan, hence these are not normally recommended for use in combination with this medicine. If you are taking any of the following with this medicine you should have regular blood tests to monitor the amount of potassium in your blood:
- ACE inhibitors (eg captopril)
- potassium-sparing diuretics (eg spironolactone, triamterene, amiloride)
- potassium salts, eg potassium citrate
- potassium supplements
- potassium-containing salt substitutes (eg Lo-Salt)
Hydrochlorothiazide can decrease blood potassium levels. If this medicine is taken with other medicines that can lower blood potassium this effect may be enhanced. Such medicines include the following:
- other diuretics
- 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 also 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.
This medicine may increase the blood level of the medicine lithium and for this reason, it is not normally recommended for people taking lithium. People taking this medicine in combination with lithium should have the level of lithium in their blood closely monitored.
Olmesartan may possibly enhance the blood sugar lowering effect of insulin and oral antidiabetic medicines, and so could increase the risk of low blood sugar (hypoglycaemia). On the other hand, hydrochlorothiazide may increase blood sugar levels. People with diabetes should therefore carefully monitor their blood sugar while taking this medicine, particularly in the first few weeks of treatment.
This medicine should not be taken within four hours of the following medicines, as if they are taken at the same time they may reduce the absorption of hydrochlorothiazide from the gut:
Hydrochlorothiazide may increase the risk of side effects caused by the following medicines:
- chemotherapy medicines, eg methotrexate, cyclophosphamide.
Hydrochlorothiazide can increase blood calcium levels. If you take calcium or vitamin D supplements regularly with this medicine your blood calcium levels should be monitored.
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.