Aliskiren – the only direct renin inhibitor which is clinically used as an antihypertensive drug. Aliskiren is the first of a new class of antihypertensive agents. Aliskiren is a new renin inhibitor of a novel structural class that has recently been shown to be efficacious in hypertensive patients after once-daily oral dosing. In short-term studies, it was effective in lowering blood pressure either alone or in combination with valsartan and hydrochlorothiazide, and had a low incidence of serious adverse effects. It was approved by the Food and Drug Administration in 2007 for the use as a monotherapy or in combination with other antihypertensives. Aliskiren is marketed under the trade name Tekturna. Aliskiren effectively reduces functional plasma renin activity by binding to renin with high affinity, preventing it from converting angiotensinogen to angiotensin I. The inhibition of renin by aliskiren is associated with a reduction in circulating levels of angiotensin I and II, with a resultant increase in plasma renin concentration and inhibit activation of mitogen-activated protein kinases ERK1 (p44) and ERK2 (p42).

Olmesartan medoxomil, a prodrug, is hydrolyzed to olmesartan during absorption from the gastrointestinal tract. Olmesartan is a selective AT1 subtype angiotensin II receptor antagonist. Olmesartan blocks the vasoconstrictor effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT1 receptor in vascular smooth muscle. Oral olmesartan medoxomil 10-40 mg once daily is recommended for the treatment of adult patients with hypertension, this dosage has consistently helped achieve a double-digit reduction both in systolic and diastolic blood pressure, a reduction which is maintained for one year. Extensive clinical evidence from several large well designed trials and the clinical practice setting has confirmed the antihypertensive efficacy and good tolerability profile of oral olmesartan medoxomil, as monotherapy in patients with hypertension. Olmesartan medoxomil has shown no clinically important pharmacokinetic interactions with digoxin, warfarin or antacid (aluminium magnesium hydroxide). Adverse events were infrequent in clinical studies of olmesartan medoxomil and were similar to those attributed to placebo.

Candesartan is classified as an angiotensin II receptor type 1 antagonist. Candesartan is an orally active lipophilic drug and possesses rapid oral absorption. It causes a reduction in blood pressure and is used in the treatment of hypertension. It is also used in the treatment of congestive heart failure and given as prophylaxis to reduce the severity and duration of migraine. Candesartan cilexetil, a prodrug of Candesartan, is available in the market under the trade names Atacand, Amias. Candesartan cilexetil is rapidly converted to candesartan, its active metabolite, during absorption from the gastrointestinal tract. Candesartan confers blood pressure lowering effects by antagonizing the hypertensive effects of angiotensin II via the RAAS (renin–angiotensin–aldosterone system). RAAS is a homeostatic mechanism for regulating hemodynamics, water, and electrolyte balance. During sympathetic stimulation or when renal blood pressure or blood flow is reduced, renin is released from granular cells of the juxtaglomerular apparatus in the kidneys. Renin cleaves circulating angiotensinogen to angiotensin I, which is cleaved by angiotensin converting enzyme (ACE) to angiotensin II. Angiotensin II increases blood pressure by increasing total peripheral resistance, increasing sodium and water reabsorption in the kidneys via aldosterone secretion, and altering the cardiovascular structure. Angiotensin II binds to two receptors: type-1 angiotensin II receptor (AT1) and type-2 angiotensin II receptor (AT2). Candesartan selectively blocks the binding of angiotensin II to AT1 in many tissues including vascular smooth muscle and the adrenal glands. This inhibits the AT1-mediated vasoconstrictive and aldosterone-secreting effects of angiotensin II and results in an overall decrease in blood pressure. Candesartan is greater than 10,000 times more selective for AT1 than AT2.

Trandolapril is a non-sulhydryl prodrug that belongs to the angiotensin-converting enzyme (ACE) inhibitor class of medications. It is metabolized to its biologically active diacid form, trandolaprilat, in the liver. Trandolaprilat inhibits ACE, the enzyme responsible for the conversion of angiotensin I (ATI) to angiotensin II (ATII). ATII regulates blood pressure and is a key component of the renin-angiotensin-aldosterone system (RAAS). Trandolapril may be used to treat mild to moderate hypertension, to improve survival following myocardial infarction in clinically stable patients with left ventricular dysfunction, as an adjunct treatment for congestive heart failure, and to slow the rate of progression of renal disease in hypertensive individuals with diabetes mellitus and microalbuminuria or overt nephropathy. Trandolapril is marketed by Abbott Laboratories under the brand name Mavik.

Moexiprilat is the pharmacologically active metabolite of Moexipril. Formation of Moexiprilat is caused by hydrolysis of a Moexipril’s ethyl ester group. Moexiprilat competitively inhibits ACE, thereby blocking the conversion of angiotensin I to angiotensin II. This prevents the actions of the potent vasoconstrictor angiotensin II and leads to vasodilatation. This agent also prevents angiotensin II-induced aldosterone secretion by the adrenal cortex, thereby promoting diuresis and natriuresis. Moexiprilat showed an extended duration of action owing to a long terminal pharmacokinetic half-life and produced a persistent ACE inhibition.

Losartan is a selective, competitive angiotensin II receptor type 1 (AT1) antagonist. Losartant is recommended as one of several preferred agents for the initial management of hypertension. Administration of losartan reduces the risk of stroke in patients with hypertension and left ventricular hypertrophy. Losartan is indicated for the treatment of diabetic nephropathy with an elevated serum creatinine and proteinuria in patients with type 2 diabetes and a history of hypertension.

Perindoprilat is a metabolite of perindopril. Perindopril is a long-acting angiotensin converting enzyme (ACE) inhibitor and it is used to treat high blood pressure, heart failure or stable coronary artery disease. Perindopril is designed to allow oral administration as perindoprilat is poorly absorbed from the gastrointestinal tract.

Fosinopril is a phosphinic acid-containing ester prodrug that belongs to the angiotensin-converting enzyme (ACE) inhibitor class of medications. It is rapidly hydrolyzed to fosinoprilat, its principle active metabolite. Fosinoprilat inhibits ACE, the enzyme responsible for the conversion of angiotensin I (ATI) to angiotensin II (ATII). ATII regulates blood pressure and is a key component of the renin-angiotensin-aldosterone system (RAAS). Fosinopril may be used to treat mild to moderate hypertension, as an adjunct in the treatment of congestive heart failure, and to slow the rate of progression of renal disease in hypertensive individuals with diabetes mellitus and microalbuminuria or overt nephropathy.

Quinapril is the hydrochloride salt of quinapril, the ethyl ester of a non-sulfhydryl, angiotensin-converting enzyme (ACE) inhibitor, quinaprilat. Quinapril hydrochloride is a white to off-white amorphous powder that is freely soluble in aqueous solvents. Quinapril is indicated for the treatment of high blood pressure (hypertension) and as adjunctive therapy in the management of heart failure. It may be used for the treatment of hypertension by itself or in combination with thiazide diuretics, and with diuretics and digoxin for heart failure.

BENAZEPRIL, (±)- is an impurity referred to as Related Compound B, which is a diastereomer of benazepril, an ACE inhibitor, under the brand name Lotensin used primarily in treatment of hypertension, congestive heart failure, and heart attacks, and also in preventing the renal and retinal complications of diabetes. BENAZEPRIL, (±)- is used as USP Reference Standard.