Telmisartan

Telmisartan belongs to a class of medicines called angiotensin-II receptor blockers, and it works by interrupting one of the body's key blood pressure control systems. Normally, an enzyme called angiotensin-converting enzyme (ACE) converts angiotensin-I into angiotensin-II, a hormone that is the main driver of the renin-angiotensin system. Angiotensin-II raises blood pressure in several ways: it narrows blood vessels, triggers the adrenal glands to produce and release aldosterone, stimulates the heart, and causes the kidneys to hold on to more sodium.

Telmisartan does not stop angiotensin-II from being made. Instead, it works further downstream by selectively blocking the AT1 receptor, the site where angiotensin-II would normally attach to produce its effects on tissues such as vascular smooth muscle and the adrenal gland. By preventing angiotensin-II from binding to this receptor, telmisartan blocks its ability to constrict blood vessels and stimulate aldosterone release, regardless of how the angiotensin-II was produced in the first place.

Telmisartan is highly selective for the AT1 receptor, binding to it more than 3,000 times as strongly as to the related AT2 receptor. Unlike ACE inhibitors, telmisartan does not block the enzyme kininase-II (the same enzyme as ACE), so it does not interfere with the breakdown of bradykinin, a substance involved in other bodily responses. It also does not act on other hormone receptors or ion channels known to play a role in regulating the cardiovascular system.