Olmesartan (also known as CS-866) is a synthetic antagonist of the Angiotensin II type 1 receptor. It has an effective concentration of 1 nM – 1 μM and an IC50 of 7.7 nM for bovine adrenal cortical membranes. After administration, Olmesartan is rapidly de-esterified within the gastrointestinal tract to form RNH-6270, a competitive Angiotensin receptor antagonist with high affinity for the receptor. The P-450 enzyme system is not involved in the conversion of CS-866 to its active metabolite. It has been shown that Olmesartan’s pharmacokinetics is suitable for administration once a day. The half-life of the drug is approximately 13 hours which places Olmesartan in the mid-range in terms of half-life compared with other Angiotensin antagonists. Olmesartan induces a beneficial anti-hypertensive effect about two weeks after the beginning of therapy. It is effective in patients of all age groups causing a mean blood pressure reduction of 12 mm Hg in DBP and 15 mm Hg in SBP when administered at a dosage of 20 mg
