Telmisartan

Indications
Telmisartan is an angiotensin II receptor blocker (ARB) indicated for treatment of hypertension and Cardiovascular (CV) risk reduction in patients who are indicated for ACE inhibitors.

Therapeutic Class
Angiotensin-ll receptor blocker

Pharmacology
Angiotensin II is formed from angiotensin I in a reaction catalyzed by angiotensin-converting enzyme (ACE, kininase II). Angiotensin II is the principal pressor agent of the renin-angiotensin system, with effects that include vasoconstriction, stimulation of synthesis and release of aldosterone, cardiac stimulation, and renal reabsorption of sodium. Telmisartan blocks the vasoconstrictor and aldosterone-secreting effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT1 receptor in many tissues, such as vascular smooth muscle and the adrenal gland. Its action is therefore independent of the pathways for angiotensin II synthesis.
There is also an AT2 receptor found in many tissues, but AT2 is not known to be associated with cardiovascular homeostasis. Telmisartan has a much greater affinity ( > 3,000 fold) for the AT1 receptor than for the AT2 receptor.
Blockade of the renin-angiotensin system with ACE inhibitors, which inhibit the biosynthesis of angiotensin II from angiotensin I, is widely used in the treatment of hypertension. ACE inhibitors also inhibit the degradation of bradykinin, a reaction also catalyzed by ACE. Because telmisartan does not inhibit ACE (kininase II), it does not affect the response to bradykinin. Whether this difference has clinical relevance is not yet known. Telmisartan does not bind to or block other hormone receptors or ion channels known to be important in cardiovascular regulation.
Blockade of the angiotensin II receptor inhibits the negative regulatory feedback of angiotensin II on renin secretion, but the resulting increased plasma renin activity and angiotensin II circulating levels do not overcome the effect of telmisartan on blood pressure.

Dosage
Hypertension: Dosage must be individualized. The usual starting dose of Telmisartan tablets is 40 mg once a day. Blood pressure response is dose-related over the range of 20 to 80 mg
Most of the antihypertensive effect is apparent within 2 weeks and maximal reduction is generally attained after 4 weeks. When additional blood pressure reduction beyond that achieved with 80 mg Telmisartan is required, a diuretic may be added.
No initial dosage adjustment is necessary for elderly patients or patients with renal impairment, including those on hemodialysis. Patients on dialysis may develop orthostatic hypotension; their blood pressure should be closely monitored.
Cardiovascular Risk Reduction: The recommended dose of Telmisartan tablets is 80 mg once a day and can be administered with or without food. It is not known whether doses lower than 80 mg of telmisartan are effective in reducing the risk of cardiovascular morbidity and mortality.
When initiating Telmisartan therapy for cardiovascular risk reduction, monitoring of blood pressure is recommended, and if appropriate, adjustment of medications that lower blood pressure may be necessary.

Administration
Telmisartan tablets may be administered with other antihypertensive agents with or without food.

Interaction
When certain medicines are taken together, there is a possibility of developing drug interactions. With Telmisartan, drugs such as potassium supplements or potassium-sparing diuretics may cause an interaction. When Telmisartan was co-administered with digoxin, median increases in digoxin peak plasma concentration (49%) and in through concentration (20%) where observed. Therefore, monitor digoxin levels when initiating, adjusting and discontinuing Telmisartan for the purpose of keeping the digoxin level within the therapeutic range. NSAID use may lead to increase risk of renal impairment and loss of antihypertensive effect. Monitor renal function periodically in patients receiving Telmisartan and NSAID therapy.

Contraindications
Telmisartan is contraindicated in conditions like Pregnancy, Adjunct in treatment of opioid dependence, Dry or painful cough. Telmisartan is also contraindicated in patients with known hypersensitivity to telmisartan.

Side Effects
Most people tolerate telmisartan well. Side effects are usually minor and either require no treatment or can easily be treated by physician. The most common telmisartan side effects include-Upper respiratory infection such as the common cold or flu up to 7 percent of people, Back pain up to 3 percent of people, Diarrhea up to 3 percent of people, Inflammation of the sinuses up to 3 percent of people.

Pregnancy & Lactation
Telmisartan has been assigned to pregnancy categories C (use during first trimester) by the FDA. When pregnancy is detected or expected, Telmisartan should be discontinued as soon as possible. The use of drugs that act directly on the RAA system during the second and third trimesters has been associated with fetal and neonatal injury, including hypotension, neonatal skull hypoplasia, anuria, reversible or irreversible renal failure and death. There are no data on the excretion of Telmisartan into human milk, due to the potential for serious adverse effects in the nursing infant, a decision should be made to discontinue nursing or discontinue the drug.

Precautions & Warnings
Use of drugs that act on the renin-angiotensin system during the second and third trimesters of pregnancy reduces fetal renal function and increases fetal and neonatal morbidity and death. Telmisartan may potentially cause extreme low blood pressure or a decrease in kidney function. Hyperkalemia may occur in patients on ARBs, particularly in patients with advanced renal impairment, heart failure, on renal replacement therapy or on potassium supplements, potassium-sparing diuretics, potassium containing salt substitutes or other drugs that increase potassium levels.

Use in Special Populations
Renal Impairment: Severe impairment or on haemodialysis: Initially, 20 mg once daily.
Hepatic Impairment: Mild to moderate: Max: 40 mg once daily. Severe: Contraindicated.

Overdose Effects
Symptoms: Hypotension, bradycardia, tachycardia, dizziness, acute renal failure and elevated serum creatinine.
Management: Supportive and symptomatic treatment. Induction of emesis and/or gastric lavage. Activated charcoal may be useful. Salt and volume replacement should be given immediately if hypotension occurs and place patient in supine position.

Storage Conditions
Store in a cool and dry place, protected from light. Keep out of children’s reach