Telmisartan for Hypertension: A Complete Guide

Overview:

Telmisartan is a medication classified within the group of angiotensin antagonists (angiotensin II receptor blockers). Telmisartan is exclusively used in treating hypertension (elevated pressure within the vessels carrying blood) and mitigating the incidence of cardiac and vascular complications. As Telmisartan blocks the angiotensin II receptor, the vasoconstrictive actions of angiotensin II are also blocked. This causes the dilation of blood vessels and, ultimately, a reduction in blood pressure. Another significant property of Telmisartan is its longer duration of action, which facilitates patient adherence to the drug. Telmisartan was approved by the United States Food and Drug Administration (USFDA) in 1998 for managing hypertension and reducing associated complications.

Dosage and Route of Administration:

• Telmisartan is available in 20 mg (milligrams), 40 mg, and 80 mg tablets.

• The starting dose given to patients with hypertension is 40 mg once daily. This dose can be maximized to 80 mg once daily, depending on the patient's blood pressure levels and tolerance.

• To mitigate the risks of cardiovascular complications, the dose given is 80 mg once daily. This preventive measure is generally prescribed for geriatric individuals who are at high risk for incidence of cardiovascular complications like stroke or infarction.

For Patients:

What Is Hypertension?

Hypertension is considered to be a chronic condition that causes elevated pressure within the blood vessels that carry blood from the heart (arteries). This develops in an individual over a long period of time when the force of blood against the artery walls is consistently over the peaks. There are several factors that interplay to cause this condition. During the early stages of the condition, there are no obvious clinical features noted in an individual. But when the pressure within the arteries increases for a chronic period, there can be various complications like vital organ damage that can ultimately result in death.

Factors Involved in Causation of Hypertension:

• Sedentary lifestyle.

• Obesity.

• Alcohol consumption.

• Genetic predisposition.

• Smoking.

• Diabetes mellitus.

• Stress.

• Poor diet plan.

What Are the Complications of Hypertension?

Persistently increased pressure buildup within the arteries can cause severe complications due to a compromise in the amount of oxygen and blood reaching all the organs. Common complications associated with hypertension are:

• Plaque deposits within arteries (atherosclerosis).

• Coronary artery disease (disease of vessels that deliver blood supply to the heart).

• Myocardial infarction (Lowered oxygen supply leading to tissue death)

• Stroke.

• Retinal damage (retinopathy).

• Kidney failure.

• Non-healing wounds.

• Peripheral neuropathy.

• Vessel wall weakening and ballooning (aneurysms).

• Vascular dementia (compromised cerebral perfusion causing decline in memory and cognition).

Why Is Telmisartan Given for Hypertension?

When an individual has hypertension for a long time, the renin-angiotensin-aldosterone system (RAAS) can become overactive. This system is responsible for stimulating the kidneys to produce renin (an enzyme) when the blood pressure drops. The produced renin acts on angiotensinogen (in the liver) to form angiotensin I. This is followed by the conversion of angiotensin I to angiotensin II (in the lungs by the action of angiotensin-converting enzymes). Angiotensin II is a very potent hormone that induces narrowing of the blood vessels throughout the body. As a result, the blood vessels (arteries) narrow further and increase the blood pressure. Also, angiotensin II causes retention and accumulation of sodium and water in the body by activating the release of aldosterone. This further exacerbates the blood pressure increase within the body.

Now, the primary objective is to block this action of angiotensin II, and this is how Telmisartan exerts its effects. As an angiotensin II receptor blocker (ARB), telmisartan operates by inhibiting the mechanism of angiotensin II. By doing so, Telmisartan can achieve the objective of reducing blood pressure by dilating the blood vessels and reducing the workload in the heart. Other than this action, Telmisartan is also considered to provide protective effects to the heart by minimizing the incidence of cardiovascular complications. Thus, the likelihood of conditions like stroke, infarction, or organ damage is greatly reduced.

How Should Telmisartan Be Taken for Treating Hypertension?

Telmisartan is available as a tablet in dosages 20 mg (milligrams), 40 mg, and 80 mg. The dose started for an individual with hypertension is generally 40 mg. The optimal antihypertensive action of Telmisartan can be achieved within four weeks. If required, the dosage of Telmisartan can be increased to 80 mg. When the results obtained are not satisfactory, a diuretic is added to the regimen to obtain a normal range of blood pressure.

Telmisartan is a drug known to have an extended period of action. So, a once-daily dosage is sufficient. Telmisartan can be taken with or without food. If the dosage of Telmisartan is missed, it should be taken as early as possible. If the duration is close to the next dosing time, the dose can be skipped.

Drug Storage and Disposal:

Telmisartan should be stored in a temperature range of 15 to 30 degrees Celsius (average 25 degrees Celsius).

Disposal:

Unused medications of Telmisartan should be placed in the same blister and returned to the pharmacist rather than direct disposal with house waste or flush.

What Are the Side Effects of Taking Telmisartan?

• Infection of the upper respiratory tract.

• Diarrhea.

• Sinusitis (Sinus inflammation).

• Pharyngitis (Pharyngeal swelling).

• Back pain.

• Malaise or a feeling of discomfort.

• Fatigue.

• Dizziness.

• Chest pain.

• Vomiting sensation.

• Headache.

• Indigestion.

• Increased sweating.

• Fever.

• Palpitation.

• Flatulence (Gas accumulation in stomach and intestine).

• Gastroesophageal reflux.

• Cramping in muscles (Especially legs).

• Rhinitis.

• Wheezing.

• Bronchitis (Bronchial inflammation).

• Bleeding nose.

• Breathing difficulties.

• Rashes on the skin.

• Itching.

• Vision problems.

• Sudden weight gain.

Serious side effects noticed in some individuals after taking Telmisartan are:

• Increased levels of potassium in circulation (hyperkalemia).

• Swelling and edematous lips, face, and feet (angioedema).

• Kidney impairment.

• Muscular pain (myalgia).

• Exacerbation of existing liver disorders.

• Severe hypotension (low blood pressure).

• Reduced hemoglobin levels.

What Are the Precautions Needed Before Taking Telmisartan?

• One of the side effects of taking Telmisartan is the development of hypotension. This occurs especially in cases where individuals are given other antihypertensive drugs like angiotensin-converting enzyme inhibitors (ACE inhibitors) or overdosing of Telmisartan. As a result of this, patients may feel dizzy and faint. In such cases, individuals should be placed immediately in the supine position (lying position). In advanced cases, such patients may require an infusion of normal saline through an intravenous (IV) route.

• Medications like non-steroidal anti-inflammatory drugs and other antihypertensives (like diuretics) can interact with Telmisartan. So, informing the doctor regarding the intake of other medicines is necessary.

• Having an insight into the functioning of the kidney and liver is very important prior to the initiation of treatment with Telmisartan, as the drug can cause or exacerbate existing conditions. This can be done through kidney and liver function tests.

• Individuals taking Telmisartan should always stay hydrated to prevent any imbalance in the electrolyte levels in the body.

For Doctors:

Indications:

• Individuals with hypertension (either given alone or given along with a diuretic for improved action). The common dose given for this population is 40 mg (milligrams) to 80 mg once daily.

• Prevention of cardiovascular complications (like stroke or infarction). The recommended dose for this action is 80 mg once daily.

Contraindications:

• Pregnant women.

• Severe dysfunction of the liver.

• Kidney damage or failure.

• Biliary obstruction.

• Stenosis of the renal artery (unilateral or bilateral).

• Children under 18 years of age.

Clinical Pharmacology:

Telmisartan, a drug belonging to the angiotensin II receptor antagonist class, exerts its pharmacological effects by selectively blocking the angiotensin II type 1 (AT1) receptor, thus inhibiting the constrictive and aldosterone-secreting effects of angiotensin II. This action leads to vasodilation of the arteries, thus resulting in a decrease in blood pressure (antihypertensive action). Additionally, blocking angiotensin II can help to prevent or reverse damage to blood vessels and organs caused by hypertension (protective or preventive action by reducing the likelihood of associated cardiovascular complications).

Drug Ingredients:

Active Ingredient: Telmisartan (4'-[(1,4'-dimethyl-2'-propyl [2,6'-bi-1H-benzimidazol]-1' yl)methyl]-[1,1'-biphenyl]-2-carboxylic acid)

Inactive Ingredients:

• Meglumine.

• Povidone.

• Sodium hydroxide.

• Sorbitol.

• Magnesium stearate.

Half-Life:

The half-life of Telmisartan is approximately 24 hours.

Pharmacokinetics:

Absorption:

After taking oral dosage, Telmisartan is well-absorbed from the gastrointestinal tract. The peak plasma concentration of Telmisartan is achieved within 0.5 to one hour after intake. Unlike some other angiotensin II receptor blockers (ARBs), Telmisartan does not require activation by the liver to exert its pharmacological effects. There are no specific side effects with food ingestion. Telmisartan's absorption is characterized by high bioavailability, with plasma levels proportional to the administered dose over a wide range.

Distribution:

Telmisartan has a high affinity to plasma proteins (albumin and alpha 1 acid glycoprotein). The percentage of binding to plasma proteins is approximately 99.5 percent. Telmisartan is also highly lipophilic. So, it can easily penetrate tissues and organs. Additionally, Telmisartan easily crosses the blood-brain barrier, enabling its effects within the central nervous system. Due to its extensive protein binding and slow dissociation from the angiotensin I receptor, Telmisartan exhibits a prolonged duration of action, contributing to its sustained antihypertensive effects. Thus, the distribution of Telmisartan is primarily influenced by plasma protein levels and tissue perfusion, with minimal accumulation in tissues following chronic administration.

Metabolism:

Metabolism of Telmisartan is done in the liver by the process of conjugation. This process renders inactive metabolites, which are removed through bile and feces.

Excretion:

More than 97 percent of the drug Telmisartan and its metabolites are transported into bile ducts and ultimately excreted in feces. Less than one percent is removed through urine.

Pharmacodynamics:

Telmisartan exerts its pharmacodynamic effects primarily by selectively blocking the angiotensin II type 1 receptor. By antagonizing the effects of angiotensin II, Telmisartan promotes vasodilation, leading to a decrease in systemic vascular resistance and blood pressure. This vasodilatory effect is particularly prominent in resistant arteries and arterioles, resulting in decreased peripheral vascular resistance. Telmisartan's blockade of the AT1 receptor also prevents angiotensin II-induced release of aldosterone, reducing sodium and water retention and further contributing to its antihypertensive effects. Additionally, Telmisartan has been shown to have pleiotropic effects beyond blood pressure reduction, including anti-inflammatory, antioxidant, and anti-proliferative properties, which may confer additional cardiovascular benefits.

Clinical Toxicity:

• Potassium levels in the blood increase after intake of Telmisartan (Hyperkalemia). This is because the aldosterone secretion is reduced due to Telmisartan. Aldosterone normally stimulates the kidneys to excrete potassium into the urine, so when its levels are reduced, potassium retention can occur.

• Telmisartan can also cause renal damage or exacerbate existing kidney disease. Renal dysfunction is mainly due to the vasodilatory effects of Telmisartan that compromise the renal blood flow.

• Hypotension is another effect seen due to overdosage or usage of other antihypertensives and diuretics.

Common Side Effects Noted With Telmisartan Usage Are:

• Ulceration of skin.

• Sinusitis.

• Back pain.

• Diarrhea.

• Respiratory and urinary tract infection.

• Insomnia.

• Migraine.

• Vertigo.

• Abdominal pain.

• Numbness.

• Fungal infection.

• Otitis media.

• Gastric reflux.

• Tinnitus.

• Conjunctivitis.

Drug Interactions:

• Combining Telmisartan with potassium-sparing diuretics can further enhance the likelihood of potassium retention within the body, thus resulting in hyperkalemia.

• Non-steroidal anti-inflammatory drugs inhibit the absorption of Telmisartan. Hence, the antihypertensive action of Telmisartan is not achieved at an optimal level. This also increases the risk of renal dysfunction.

• Telmisartan may increase serum Lithium levels, ultimately leading to lithium toxicity. Close evaluation and adjustment in the dosage of Lithium may be necessary when Telmisartan is initiated or discontinued.

• Concurrent use of Telmisartan with other agents that block the renin-angiotensin-aldosterone system (RAAS), such as angiotensin-converting enzyme inhibitors (For example, Ramipril) or direct renin inhibitors, may increase the incidence of complications.

• Telmisartan is also known to increase the levels of Digoxin within the blood. This can increase the effects of cardiac conduction.

• Cyclosporine use, along with Telmisartan, is also not indicated.

Guidelines for Specific Populations:

Pregnant and Lactating Women:

• Telmisartan is contraindicated for use during pregnancy because it has the potential to cause damage or death to the fetus. Exposure to angiotensin receptor blockers, including Telmisartan, during pregnancy, can lead to fetal malformations, fetal growth restriction, and even fetal death. Therefore, Telmisartan should not be used during pregnancy, and if pregnancy is detected, alternative antihypertensive medications that are deemed to be safe for use in pregnancy should be considered.

• Breastfeeding is generally not indicated for lactating women as there is a chance for increased incidence of hypotension and renal failure in infants. If Telmisartan is absolutely essential for such women, other modes of feeding the child should be considered.

Geriatric Individuals:

As people age, they are more likely to develop hypertension due to changes in blood vessel elasticity and other factors. Telmisartan offers several advantages for this population. The once-daily dosing regimen of Telmisartan promotes adherence, which can be exclusively advantageous for older adults who may have complex medication regimens. Additionally, Telmisartan has been shown to have a favorable safety profile in geriatric populations, with a lower incidence of adverse effects. Furthermore, Telmisartan has demonstrated cardiovascular protective effects beyond just blood pressure reduction.

Pediatric Individuals:

Telmisartan is not indicated for use in children less than 18 years of age.