Telmsartan is a drug that works by stopping the angiotensin II hormone from activating a receptor in the body, which normally leads to a slight increase in blood pressure when it gets too low. When you take a sartan drug like telmisartan, the hormone can’t work as well as usual and your blood pressure decreases, which is useful in the treatment of hypertension. It can also sometimes be used to help prevent cardiovascular disease if you have a high risk the disease.
Brand Names and Doses
Telmisartan is the genic name, the name of the active drug found in the medication, but you might know it better by the brand name, Micardis, which is available is two different doses: 40 mg and 80 mg.
Most people begin with the lower 40 mg dose and the dose can be increased to 80 mg a few weeks later if the blood pressure is still high. This helps to reduce initial side effects that may occur with this medicine.
Olmesartan is also available in combination other medications, such as amlopdipine and hydrochlorothiazide.
Twynsta is the brand name of the combination medication of telmisartan with amlodipine, which is available in four different doses:
- Telmisartan 40 mg / Amlodipine 5 mg
- Telmisartan 40 mg / Amlodipine 10 mg
- Telmisartan 80 mg / Amlodipine 5 mg
- Telmisartan 80 mg / Amlodipine 10 mg
Micardis Plus is the brand name of the combination medication of telmisartan with hydrochlorothiazide. It is available in three different doses:
- Telmisartan 40 mg / Hydrochlorothiazide 12.5 mg
- Telmisartan 80 mg / Hydrochlorothiazide 12.5 mg
- Telmisartan 80 mg / Hydrochlorothiazide 25 mg
What type of drug is it?
Telmisartan is a drug that is classed as a sartan, also sometimes known as angiotensin receptor blockers (ARB) or angiotensin receptor antagonists (ARA). The medicines in this class all work in the same way and include:
How does it work?
Telmisartan works by stopping the angiotensin II hormone from binding to a receptor in the body, blocking the reactions that usually cause an increase in blood pressure from occurring.
In an otherwise healthy person, angiotensin II plays an important role to maintain the balance of blood pressure in the normal range. If the pressure gets too low, more angiotensin II is produced, which increases the effects of the hormone and help to raise the blood pressure slightly. The smooth muscles surrounding the blood vessels contract, narrowing the passageways, and the kidneys reabsorb more water, increasing the blood volume. With more blood travelling through thinner vessels, the pressure is going to increase, restoring the normal balance in the body.
When you take telmisartan, angiotensin II doesn’t work as well to activate the receptor and the normal effects can’t occur. As a result, the opposite happens:
- The muscles around your blood vessels relax, creating more space for the blood passing through.
- Your kidneys reabsorb less water and you excrete more in your urine, reducing the volume of blood.
Less blood pumping around larger blood vessels means the pressure will become lower. If you think of it like a plumbing system, there will be less stress for your heart to pump blood around the body.
Side Effects
Sartans affect the body in various ways and there are several side effects that may occur when you take telmisartan.
Low blood pressure (hypotension)
The most common side effects happen when irbesartan is working too well and you end up with low blood pressure. You might notice:
- Headache
- Tiredness
- Dizziness
- Flushing
This is most common when you first start taking telmisartan or after a dose increase. It usually gets better within a few days as your body gets used to the medication but if the effects are still evident after a week, your blood pressure too low because the dose is too high for your body. You can simply check your blood pressure at a pharmacy and ask your doctor if you need to change or reduce the dose.
Excess Potassium (Hyperkalaemia)
Telmisartan causes more water to be excreted in the urine than usual, which can upset the balance of potassium salts in your body. Less potassium is excreted and there can be too much in your body, making you feel tired and weak. If you notice these signs, you can ask your doctor for a blood test to check if you have high potassium levels and decide what to do.
Cough
Some people also get a dry cough when they take telmisartan. If this affects you and it annoys you, talk to your doctor about alternative medication options for hypertension.
Cautions
There are a couple of things you should be aware of before you start taking telmisartan, which are listed below:
Angioedema – Swelling of your mouth and face, which is particularly dangerous if the airways become blocked. You should see a doctor as soon as possible if this occurs.
Renal Impairment – Changes to the kidney function can increase the risk of renal impairment, especially when used with other medications such as NSAIDS and diuretics. If you have poor kidney function, an alternative medication for hypertension is likely to be safer.
Stopping Suddenly – You may get rebound hypertension with even higher blood pressure than before if you suddenly stop taking the medication. This is because your body has adapted to taking the drug each day and, if you want to stop, it is best to gradually reduce the dose over a few weeks.
Drug Interactions
Lithium + Telmisartan Interaction
Telmisartan can decrease the amount of lithium that is excreted from the body and increase the risk of side effects. The dose of lithium can be reduced to help manage this, or a different antihypertensive medication can be used.
Loop Diuretic + Telmisartan Interaction
Taking a loop diuretic drug with telmisartan can increase the risk of renal impairment and blood pressure that is too low, particularly for the first few doses. It is best to take a lower dose or to stop taking the loop diuretic for a few days when beginning telmisartan.
NSAID + Telmisartan Interaction
NSAIDs and telmisartan can sometimes be used together in young and otherwise healthy patients, but it might not work as well to reduce your blood pressure and can lead to renal impairment.
Thiazide Diuretic + Telmisartan Interaction
Taking a thiazide diuretic and telmisartan together increases the risk of renal impairment and blood pressure that is too low, particularly for the first few doses. Using a lower dose is okay for some people but the combination is not recommended for others – you should talk to your doctor if you’re worried.
Pregnancy and Breastfeeding
Telmisartan should not be used by women who are pregnant or planning to become pregnant. This is because it can cause birth defects early in the pregnancy and may cause renal dysfunction to the fetus later in the pregnancy.
It is not recommended to take telmisartan while breastfeeding because there is limited research data available and we don’t know if it is safe for you or your baby.
