Pharmacology: Pharmacodynamics and Pharmacokinetics: Telmisartan is an orally active and specific Angiotensin II receptor (type AT1) antagonist.
Telmisartan displaces angiotensin II with very high affinity from its binding site at the AT1 receptor subtype, which is responsible for the known actions of angiotensin II. Telmisartan does not exhibit any partial agonist activity at the AT1 receptor. Telmisartan selectively binds the AT1 receptor. The binding is long-lasting. Telmisartan does not show affinity for other receptors, including AT2 and other less characterized AT receptors. The functional role of these receptors is not known, nor is the effect of their possible overstimulation by angiotensin II, whose levels are increased by Telmisartan. Telmisartan does not inhibit human plasma renin or block ion channels. Telmisartan does not inhibit angiotensin converting enzyme (kininase II), the enzyme which also degrades bradykinin. Therefore, it is not expected to potentiate bradykinin-mediated adverse effects. In human, an 80 mg dose of Telmisartan almost completely inhibits the angiotensin II evoked blood pressure increase. The inhibitory effect is maintained over 24 hours and still measurable up to 48 hours.
Telmisartan is rapidly absorbed from the gastrointestinal tract, the absolute oral bioavailability is dose dependent and is about 42% after a 40 mg dose and 58% after a 160 mg dose. Peak plasma concentrations of Telmisartan are reached about 0.5 to 1 hour after an oral dose. Telmisartan is over 90% bound to plasma proteins. It is excreted almost entirely in the faeces via bile, mainly as unchanged drug. The terminal half-life of Telmisartan is about 24 hours.
It is used in the management of hypertension.
In hypertension, Telmisartan is given in an initial dose of 40 mg once daily. This may be increased if necessary to a maximum dose of 80 mg once daily. Lower doses should be considered in patients with hepatic or renal impairment. Or as prescribed by a physician.
There is limited information available with regard to overdose in humans. Symptoms: The most prominent manifestations of Telmisartan overdose were hypotension and tachycardia; bradycardia, dizziness, increase in serum creatinine, and acute renal failure have also been reported. Treatment: Telmisartan is not removed by haemodialysis. The patient should be closely monitored, and the treatment should be symptomatic and supportive.
Management depends on the time since ingestion and the severity of the symptoms. Suggested measures include induction of emesis and/or gastric lavage. Activated charcoal may be useful in the treatment of overdose. Serum electrolytes and creatinine should be monitored frequently. If hypotension occurs, the patient should be placed in a supine position, with salt and volume replacement given quickly.
Contraindicated in pregnancy.
Telmisartan should be used with caution in patients with hepatic impairment or biliary obstruction.
Pregnancy:
Angiotensin II receptor antagonists should not be initiated during pregnancy. Unless continued angiotensin II receptor antagonist therapy is considered essential, patients planning pregnancy should be changed to alternative antihypertensive treatments which have an established safety profile for use in pregnancy. When pregnancy is diagnosed, treatment with angiotensin II receptor antagonists should be stopped immediately, and, if appropriate, alternative therapy should be started.
Epidemiological evidence regarding the risk of teratogenicity following exposure to ACE inhibitors during the first trimester of pregnancy has not been conclusive; however, a small increase in risk cannot be excluded. Whilst there is no controlled epidemiological data on the skin risk with angiotensin II receptor antagonist, similar risks may exit for this class of drugs. Should exposure to angiotensin II receptor antagonists have occurred from the second trimester of pregnancy, ultrasound check of renal function and skull is recommended.
Breastfeeding: Because no information is available regarding the use of Telmisartan during breastfeeding, Telmisartan is not recommended and alternative treatments with better established safety profiles during breastfeeding are preferable,
especially while nursing a newborn or preterm infant.
Adverse effects of telmisartan have been reported to be usually mild and transient, and include dizziness, headache, and dose-related orthostatic hypotension. Hypotension may occur particularly in patients with volume depletion (for example those who have received high-dose diuretics). Impaired renal function and, rarely, rash, urticaria, pruritus, angioedema, and raised liver enzyme values may occur. Hyperkalaemia, myalgia, and arthralgia have been reported. Telmisartan appears less likely than ACE inhibitors to cause cough. Other adverse effects that have been reported with angiotensin II receptor antagonists include respiratory tract disorders, back pain, gastrointestinal disturbances, fatigue, and neutropenia. Rhabdomyolysis has been reported rarely.
The antihypertensive effects of Telmisartan may be potentiated by drugs or other agents that lower blood pressure. An additive hyperkalaemic effect is possible with potassium supplements, potassium-sparing diuretics or other drugs that can cause hyperkalaemia. Telmisartan and potassium-sparing diuretics should not generally be given together. NSAIDs should be used with caution in patients taking Telmisartan as the risk of renal impairment may be increased particularly in those who are inadequately hydrated. Use of NSAIDs may also attenuate the hypotensive effect of Telmisartan. Telmisartan and some other angiotensin II receptor antagonists are metabolized by cytochrome P450 isoenzymes and interactions may occur with drugs that affect these enzymes. Telmisartan may increase serum concentrations of Digoxin but the interaction is probably not clinically significant.
C09CA07 - telmisartan ; Belongs to the class of angiotensin II receptor blockers (ARBs). Used in the treatment of cardiovascular disease.
Mizar tab 80 mg
100's (P2,100/box, P21/tab)
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