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ACE inhibitor

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Template:Short description Template:Redirect Template:Distinguish Template:Cs1 config Template:Infobox drug class Angiotensin-converting-enzyme inhibitors (ACE inhibitors) are a class of medication used primarily for the treatment of high blood pressure and heart failure.<ref name="Kaplans Essentials of Cardiac Anesthesia 2018 p. ">Template:Cite book</ref><ref name="Aronow 2010 pp. 327–337">Template:Cite book</ref> This class of medicine works by causing relaxation of blood vessels as well as a decrease in blood volume, which leads to lower blood pressure and decreased oxygen demand from the heart.

ACE inhibitors inhibit the activity of angiotensin-converting enzyme, an important component of the renin–angiotensin system which converts angiotensin I to angiotensin II,<ref name="Byrd Ram Lerma 2019 pp. 477–482">Template:Cite book</ref> and hydrolyses bradykinin.<ref name="Kaplans Essentials of Cardiac Anesthesia 2018 p. "/> Therefore, ACE inhibitors decrease the formation of angiotensin II, a vasoconstrictor, and increase the level of bradykinin, a peptide vasodilator.<ref name="Kaplans Essentials of Cardiac Anesthesia 2018 p. "/><ref name="Byrd Ram Lerma 2019 pp. 477–482"/> This combination is synergistic in lowering blood pressure.<ref name="Kaplans Essentials of Cardiac Anesthesia 2018 p. "/><ref name="Byrd Ram Lerma 2019 pp. 477–482"/>

As a result of inhibiting the ACE enzyme in the bradykinin system, the ACE inhibitor drugs allow for increased levels of bradykinin which would normally be degraded. Bradykinin produces prostaglandin. This mechanism can explain the two most common side effects seen with ACE Inhibitors: angioedema and cough.

Frequently prescribed ACE inhibitors include benazepril, zofenopril, perindopril, trandolapril, captopril, enalapril, lisinopril, and ramipril.Template:TOC limit

Medical useEdit

ACE inhibitors were initially approved for the treatment of hypertension and can be used alone or in combination with other anti-hypertensive medications. Later, they were found useful for other cardiovascular and kidney diseases<ref name="Goodman-Gilman">Template:Cite book</ref> including:

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  • Heart failure (left ventricular systolic dysfunction)<ref>{{#invoke:citation/CS1|citation

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In treating high blood pressure, ACE inhibitors are often the first drug choice, particularly when diabetes is present,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> but age can lead to different choices and it is common to need more than one drug to obtain the desired improvement. There are fixed-dose combination drugs, such as ACE inhibitor and thiazide combinations. ACE inhibitors have also been used in chronic kidney failure and kidney involvement in systemic sclerosis (hardening of tissues, as scleroderma renal crisis). In those with stable coronary artery disease, but no heart failure, benefits are similar to other usual treatments.<ref>Template:Cite journal</ref>

In 2012, a meta-analysis published in the BMJ described the protective role of ACE inhibitors in reducing the risk of pneumonia when compared to angiotensin II receptor blocker (ARBs).<ref name="Caldeira Alarcao Vaz-Carneiro Costa pp. e4260–e4260">Template:Cite journal</ref> The authors found a decreased risk in patients with previous stroke (54% risk reduction), with heart failure (37% risk reduction), and of Asian descent (43% risk reduction vs 54% risk reduction in non-Asian population). However, no reduced pneumonia-related mortality was observed.<ref>Template:Cite journal</ref>

OtherEdit

ACE inhibitors may also be used to help decrease excessive water consumption in people with schizophrenia resulting in psychogenic polydipsia.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref> A double-blind, placebo-controlled trial showed that when used for this purpose, enalapril led to decreased consumption (determined by urine output and osmolality) in 60% of people;<ref>Template:Cite journal</ref> the same effect has been demonstrated in other ACE inhibitors.<ref>Template:Cite journal</ref>

Additionally ACE-I are commonly used after renal transplant to manage post-transplant erythrocytosis, a condition characterised by a persistently high hematocrit greater than 51% which often develops 8–24 months after successful transplantation,<ref>Template:Cite journal</ref> as ACE-I have been shown to decrease erythropoietin production.<ref>Template:Cite journal</ref>

Adverse effectsEdit

Common side effects include: low blood pressure, cough, hyperkalemia, headache, dizziness, fatigue, nausea, and kidney impairment.<ref name="AMH2006">Template:Cite book Template:Page needed</ref><ref name="Sidorenkov & Navis 2014">Template:Cite journal</ref>

The main adverse effects of ACE inhibition can be understood from their pharmacological action. The other reported adverse effects are liver problems and effects on the fetus.<ref name="Sidorenkov & Navis 2014"/> Kidney problems may occur with all ACE inhibitors that directly follows from their mechanism of action. Patients starting on an ACE inhibitor usually have a modest reduction in glomerular filtration rate (GFR).<ref name="Tucker Perazella 2019 pp. 78–83">Template:Cite book</ref> However, the decrease may be significant in conditions of pre-existing decreased renal perfusions, such as renal artery stenosis, heart failure, polycystic kidney disease, or volume depletion. In these patients, the maintenance of GFR depends on angiotensin-II-dependent efferent vasomotor tone.<ref name="Tucker Perazella 2019 pp. 78–83"/> Therefore, renal function should be closely monitored over the first few days after initiation of treatment with ACE inhibitor in patients with decreased renal perfusion.<ref name="Sidorenkov & Navis 2014"/> Generally, a moderate reduction in renal function (no greater than 30% rise in serum creatinine which stabilizes within 2-4 weeks) is considered acceptable as part of the therapeutic effect.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

Reduced GFR is especially a problem if the patient is concomitantly taking an NSAID and a diuretic.<ref name="Byrd Ram Lerma 2019 pp. 477–482 II"/> When the three drugs are taken together, the risk of developing renal failure is significantly increased.<ref name="Thomas2000">Template:Cite journal</ref>

High blood potassium is another possible complication of treatment with an ACE inhibitor due to its effect on aldosterone. Suppression of angiotensin II leads to a decrease in aldosterone levels. Since aldosterone is responsible for increasing the excretion of potassium, ACE inhibitors can cause retention of potassium. Some people, however, can continue to lose potassium while on an ACE inhibitor.<ref name="Cohn2000">Template:Cite journal</ref> Hyperkalemia may decrease the velocity of impulse conduction in the nerves and muscles, including cardiac tissues. This leads to cardiac dysfunction and neuromuscular consequences, such as muscle weakness, paresthesia, nausea, diarrhea, and others. Close monitoring of potassium levels is required in patients receiving treatment with ACE inhibitors who are at risk of hyperkalemia.<ref name="Sidorenkov & Navis 2014"/>

Another possible adverse effect specific for ACE inhibitors, but not for other RAAS blockers, is an increase in bradykinin level.<ref name="Sidorenkov & Navis 2014"/>

A persistent dry cough is a relatively common adverse effect believed to be associated with the increases in bradykinin levels produced by ACE inhibitors, although the role of bradykinin in producing these symptoms has been disputed.<ref name="Okumura2001">Template:Cite journal</ref> Many cases of cough in people on ACE inhibitors may not be from the medication itself, however.<ref>Template:Cite journal</ref> People who experience this cough are often switched to angiotensin II receptor antagonists.Template:Citation needed

Some (0.7%)<ref name="Byrd Ram Lerma 2019 pp. 477–482 II"/> develop angioedema due to increased bradykinin levels.<ref>Template:Cite journal</ref> A genetic predisposition may exist.<ref name="Molinaro2002">Template:Cite journal</ref>

A severe rare allergic reaction can affect the bowel wall and secondarily cause abdominal pain.<ref>Template:Cite journal</ref>

BloodEdit

Hematologic effects, such as neutropenia, agranulocytosis and other blood dyscrasias, have occurred during therapy with ACE inhibitors, especially in people with additional risk factors.<ref>FDA Prescribing information, http://www.rxmed.com/b.main/b2.pharmaceutical/b2.1.monographs/CPS-%20Monographs/CPS-%20%28General%20Monographs-%20A%29/ACE%20INHIBITORS.html</ref>

PregnancyEdit

In pregnant women, ACE inhibitors taken during all the trimesters have been reported to cause congenital malformations, stillbirths, and neonatal deaths. Commonly reported fetal abnormalities include hypotension, renal dysplasia, anuria/oliguria, oligohydramnios, intrauterine growth retardation, pulmonary hypoplasia, patent ductus arteriosus, and incomplete ossification of the skull.<ref name="Sidorenkov & Navis 2014"/><ref name="pmid9520613">Template:Cite journal</ref> Overall, about half of newborns exposed to ACE inhibitors are adversely affected, leading to birth defects.<ref>Template:Cite journal</ref><ref name="Byrd Ram Lerma 2019 pp. 477–482 II"/>

ACE inhibitors are ADEC pregnancy category D and should be avoided in women who are likely to become pregnant.<ref name="AMH2006" /> In the U.S., ACE inhibitors must be labeled with a boxed warning concerning the risk of birth defects when taken during the second and third trimester. Their use in the first trimester is also associated with a risk of major congenital malformations, particularly affecting the cardiovascular and central nervous systems.<ref name="Cooper2006">Template:Cite journal</ref>

OverdoseEdit

Symptoms and Treatment: There are few reports of ACE inhibitor overdose in the literature. The most likely manifestations are hypotension, which may be severe, hyperkalemia, hyponatremia and renal impairment with metabolic acidosis. Treatment should be mainly symptomatic and supportive, with volume expansion using normal saline to correct hypotension and improve renal function, and gastric lavage followed by activated charcoal and a cathartic to prevent further absorption of the drug. Captopril, enalapril, lisinopril and perindopril are known to be removable by hemodialysis.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Contraindications and precautionsEdit

The ACE inhibitors are contraindicated in people with:Template:Citation needed

  • Pregnancy or breastfeeding
  • Previous angioedema associated with ACE inhibitor therapy
  • Bilateral renal artery stenosis<ref>{{#invoke:citation/CS1|citation

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  • Hypersensitivity to ACE inhibitors<ref name="ACEI contraindications"/>

ACE inhibitors should be used with caution in people with:Template:Citation needed

A combination of ACE inhibitor with other drugs may increase effects of these drugs, but also the risk of adverse effects.<ref name="Sidorenkov & Navis 2014"/> The commonly reported adverse effects of drug combination with ACE inhibitor are acute renal failure, hypotension, and hyperkalemia. The drugs interacting with ACE inhibitor should be prescribed with caution. Special attention should be given to combinations of ACE inhibitor with other RAAS blockers, diuretics (especially potassium-sparing diuretics), NSAIDs, anticoagulants, cyclosporine, DPP-4 inhibitors, and potassium supplements.

Potassium supplementation should be used with caution and under medical supervision owing to the hyperkalemic effect of ACE inhibitors.<ref name="pmid11044229">Template:Cite journal</ref>

Concomitant use with cyclooxygenase inhibitors tends to decrease ACE inhibitor's hypotensive effect.<ref name="Sear 2019 pp. 535–555">Template:Cite book</ref><ref name="Byrd Ram Lerma 2019 pp. 477–482 II">Template:Cite book</ref>

Mechanism of actionEdit

ACE inhibitors reduce the activity of the renin–angiotensin–aldosterone system (RAAS) as the primary etiologic (causal) event in the development of hypertension in people with diabetes mellitus, as part of the insulin-resistance syndrome or as a manifestation of renal disease.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

Renin–angiotensin–aldosterone systemEdit

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File:Renin-angiotensin-aldosterone system.svg
Renin–angiotensin–aldosterone system

The renin–angiotensin–aldosterone system is a major blood pressure regulating mechanism. Markers of electrolyte and water imbalance in the body such as hypotension, low distal tubule sodium concentration, decreased blood volume and high sympathetic tone trigger the release of the enzyme renin from the cells of juxtaglomerular apparatus in the kidney.Template:Citation needed

Renin activates a circulating liver derived prohormone angiotensinogen by proteolytic cleavage of all but its first ten amino acid residues known as angiotensin I. ACE (angiotensin converting enzyme) then removes a further two residues, converting angiotensin I into angiotensin II. ACE is found in the pulmonary circulation and in the endothelium of many blood vessels.<ref>Human Physiology, Silverthorn (Pearson Benjamin Cummings 2004)Template:Page needed</ref> The system increases blood pressure by increasing the amount of salt and water the body retains, although angiotensin II is also a potent vasoconstrictor.<ref name="Weir 1999 pp. 205–213">Template:Cite journal</ref>

EffectsEdit

ACE inhibitors block the conversion of angiotensin I (ATI) to angiotensin II (ATII).<ref name="Ogbru">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> They thereby lower arteriolar resistance and increase venous capacity; decrease cardiac output, cardiac index, stroke work, and volume; lower resistance in blood vessels in the kidneys; and lead to increased natriuresis (excretion of sodium in the urine). Renin increases in concentration in the blood as a result of negative feedback of conversion of ATI to ATII. ATI increases for the same reason; ATII and aldosterone decrease. Bradykinin increases because of less inactivation by ACE.Template:Citation needed

Under normal conditions, angiotensin II has these effects:Template:Cn

  • Vasoconstriction (narrowing of blood vessels) and vascular smooth muscle hypertrophy (enlargement) induced by ATII may lead to increased blood pressure and hypertension. Further, constriction of the efferent arterioles of the kidney leads to increased perfusion pressure in the glomeruli.
  • It contributes to ventricular remodeling and ventricular hypertrophy of the heart through stimulation of the proto-oncogenes c-fos, c-jun, c-myc, transforming growth factor beta (TGF-B), through fibrogenesis and apoptosis (programmed cell death).
  • Stimulation by ATII of the adrenal cortex to release aldosterone, a hormone that acts on kidney tubules, causes sodium and chloride ions retention and potassium excretion. Sodium is a "water-holding" ion, so water is also retained, which leads to increased blood volume, hence an increase in blood pressure.
  • Stimulation of the posterior pituitary to release vasopressin (antidiuretic hormone, ADH) also acts on the kidneys to increase water retention. If ADH production is excessive in heart failure, Na+ level in the plasma may fall (hyponatremia), and this is a sign of increased risk of death in heart failure patients.
  • A decrease renal protein kinase C

During the course of ACE inhibitor use, the production of ATII is decreased,Template:NoteTag<ref name="Gradman Traub 2007 pp. 985–1001">Template:Cite book</ref> which prevents aldosterone release from the adrenal cortex.<ref name="Gradman Traub 2007 pp. 985–1001"/> This allows the kidney to excrete sodium ions along with obligate water, and retain potassium ions. This decreases blood volume, leading to decreased blood pressure.<ref name="Gradman Traub 2007 pp. 985–1001"/>

Epidemiological and clinical studies have shown ACE inhibitors reduce the progress of diabetic nephropathy independently from their blood pressure-lowering effect.<ref name="pmid10780101">Template:Cite journal</ref> This action of ACE inhibitors is used in the prevention of diabetic renal failure.Template:Citation needed

ACE inhibitors have been shown to be effective for indications other than hypertension<ref>Template:Cite journal</ref> even in patients with normal blood pressure.<ref>Template:Cite journal</ref> The use of a maximum dose of ACE inhibitors in such patients (including for prevention of diabetic nephropathy, congestive heart failure, and prophylaxis of cardiovascular events) is justified,<ref>Template:Cite journal</ref> because it improves clinical outcomes independently of the blood pressure-lowering effect of ACE inhibitors. Such therapy, of course, requires careful and gradual titration of the dose to prevent the effects of rapidly decreasing blood pressure (dizziness, fainting, etc.).Template:Citation needed

ACE inhibitors have also been shown to cause a central enhancement of parasympathetic nervous system activity in healthy volunteers and patients with heart failure.<ref>Template:Cite journal</ref><ref>Template:Cite journalTemplate:Verify source</ref> This action may reduce the prevalence of malignant cardiac arrhythmias, and the reduction in sudden death reported in large clinical trials.<ref>Template:Cite journal</ref> ACE Inhibitors also reduce plasma norepinephrine levels, and its resulting vasoconstriction effects, in heart failure patients, thus breaking the vicious circles of sympathetic and renin angiotensin system activation, which sustains the downward spiral in cardiac function in congestive heart failureTemplate:Citation needed

The ACE inhibitor enalapril has also been shown to reduce cardiac cachexia in patients with chronic heart failure.<ref>Template:Cite journal</ref> Cachexia is a poor prognostic sign in patients with chronic heart failure.<ref>Template:Cite journal</ref> ACE inhibitors are under early investigation for the treatment of frailty and muscle wasting (sarcopenia) in elderly patients without heart failure.<ref>Template:Cite journal</ref>

ExamplesEdit

Currently, there are 10 ACE inhibitors approved for use in the United States by the FDA: captopril (1981), enalapril (1985), lisinopril (1987), benazepril (1991), fosinopril (1991), quinapril (1991), ramipril (1991), perindopril (1993), moexipril (1995) and trandolapril (1996).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

ACE inhibitors are easily identifiable by their common suffix, '-pril'. ACE inhibitors can be divided into three groups based on their molecular structure of the enzyme binding sites (sulfhydryl, phosphinyl, carboxyl) to the active center of ACE:<ref name="Shibata Fujita 2018 pp. 230–241">Template:Cite book</ref>

Sulfhydryl-containing agentsEdit

  • Alacepril<ref name="Shibata Fujita 2018 pp. 230–241"/>
  • Captopril (trade name Capoten), the first ACE inhibitor.<ref name="Shibata Fujita 2018 pp. 230–241"/>
  • Zofenopril

These agents appear to show antioxidative properties but may be involved in adverse events such as skin eruptions.<ref name="Shibata Fujita 2018 pp. 230–241"/>

Dicarboxylate-containing agentsEdit

This is the largest group, including:Template:Citation needed

Phosphonate-containing agentsEdit

Naturally occurringEdit

  • A comprehensive resource on anti-hypertensive peptides is available in form of a database. It contains around 1700 unique antihypertensive peptides<ref name="pmid25392419">Template:Cite journal</ref>
  • Arfalasin (HOE 409) is angiotensin antagonist.<ref name="Google Patents 1975">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

Dairy productsEdit

Comparative informationEdit

All ACE inhibitors have similar antihypertensive efficacy when equivalent doses are administered. The main differences lie with captopril, the first ACE inhibitor. Captopril has a shorter duration of action and an increased incidence of adverse effects. It is also capable of passing through the blood–brain barrier.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

In a large clinical study, one of the agents in the ACE inhibitor class, ramipril (Altace), demonstrated an ability to reduce the mortality rates of patients with a myocardial infarction and to slow the subsequent development of heart failure. This finding was made after it was discovered that regular use of ramipril reduced mortality rates even in test subjects who did not have hypertension.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Some believe ramipril's additional benefits may be shared by some or all drugs in the ACE-inhibitor class. However, ramipril currently remains the only ACE inhibitor for which such effects are actually evidence-based.<ref>Template:Cite journal</ref>

A meta-analysis confirmed that ACE inhibitors are effective and certainly the first-line choice in hypertension treatment. This meta-analysis was based on 20 trials and a cohort of 158,998 patients, of whom 91% were hypertensive. ACE inhibitors were used as the active treatment in seven trials (n=76,615) and angiotensin receptor blocker (ARB) in 13 trials (n=82,383). ACE inhibitors were associated with a statistically significant 10% mortality reduction: (HR 0.90; 95% CI, 0.84–0.97; P=0.004). In contrast, no significant mortality reduction was observed with ARB treatment (HR 0.99; 95% CI, 0.94–1.04; P=0.683). Analysis of mortality reduction by different ACE inhibitors showed that perindopril-based regimens are associated with a statistically significant 13% all-cause mortality reduction. Taking into account the broad spectrum of the hypertensive population, one might expect that an effective treatment with ACE inhibitors, in particular with perindopril, would result in an important gain of lives saved.<ref>Template:Cite journal</ref>

Equivalent doses in hypertensionEdit

The ACE inhibitors have different strengths with different starting dosages. Dosage should be adjusted according to the clinical response.<ref>What are the dose comparisons of all ACE inhibitors used in hypertension? Template:Webarchive TripAnswers, Trip, May 25, 2007. Accessed 2009-11-21</ref><ref>Common Medication Conversions (Equivalents): Ace Inhibitors Template:Webarchive. GlobalRPh.com. Accessed 2009-11-22.</ref><ref>Treating High Blood Pressure and Heart Disease: the ACE Inhibitors. Consumer Reports Health Best Buy Drugs. June 2009.</ref>

ACE inhibitors dosages for hypertension
Dosage
Note: bid = two times a day, tid = three times a day, d = daily
Drug dosages from Drug Lookup, Epocrates Online.
Name Equivalent daily dose Start Usual Maximum
Benazepril 10 mg 10 mg 20–40 mg 80 mg
Captopril 50 mg (25 mg bid) 12.5–25 mg bid-tid 25–50 mg bid-tid 150 mg/d
Enalapril 5 mg 5 mg 10–40 mg 40 mg
Fosinopril 10 mg 10 mg 20–40 mg 80 mg
Lisinopril 10 mg 10 mg 10–40 mg 80 mg
Moexipril 7.5 mg 7.5 mg 7.5–30 mg 30 mg
Perindopril 4 mg 4 mg 4–8 mg 16 mg
Quinapril 10 mg 10 mg 20–80 mg 80 mg
Ramipril 2.5 mg 2.5 mg 2.5–20 mg 20 mg
Trandolapril 2 mg 1 mg 2–4 mg 8 mg

Combination with angiotensin II receptor antagonistsEdit

ACE inhibitors possess many common characteristics with another class of cardiovascular drugs, angiotensin II receptor antagonists, which are often used when patients are intolerant of the adverse effects produced by ACE inhibitors. ACE inhibitors do not completely prevent the formation of angiotensin II, as blockage is dose-dependent, so angiotensin II receptor antagonists may be useful because they act to prevent the action of angiotensin II at the AT1 receptor, leaving AT2 receptor unblocked; the latter may have consequences needing further study.Template:Citation needed

The combination therapy of angiotensin II receptor antagonists with ACE inhibitors may be superior to either agent alone. This combination may increase levels of bradykinin while blocking the generation of angiotensin II and its activity at the AT1 receptor. This 'dual blockade' may be more effective than using an ACE inhibitor alone, because angiotensin II can be generated via non-ACE-dependent pathways. Preliminary studies suggest this combination of pharmacologic agents may be advantageous in the treatment of essential hypertension, chronic heart failure,<ref name="dimopoulos">Template:Cite journal</ref> and nephropathy.<ref name="Luno2005">Template:Cite journal</ref><ref name="vandeWal2005">Template:Cite journal</ref> However, the more recent ONTARGET study showed no benefit of combining the agents and more adverse events.<ref>Template:Cite journal</ref> While statistically significant results have been obtained for its role in treating hypertension, clinical significance may be lacking.<ref name="Finnegan2003">Template:Cite journal</ref> There are warnings about the combination of ACE inhibitors with ARBs.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Patients with heart failure may benefit from the combination in terms of reducing morbidity and ventricular remodeling.<ref name="Krum2004">Template:Cite journal</ref><ref name="Solomon2005">Template:Cite journal</ref>

The most compelling evidence for the treatment of nephropathy has been found: This combination therapy partially reversed the proteinuria and also exhibited a renoprotective effect in patients with diabetic nephropathy,<ref name="Luno2005"/> and pediatric IgA nephropathy.<ref name="Yang2005">Template:Cite journal</ref>

HistoryEdit

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Leonard T. Skeggs and his colleagues (including Norman Shumway) discovered ACE in plasma in 1956.<ref name=Bernstein>Template:Cite journal</ref> It was also noted that those who worked in banana plantations in South-western Brazil collapsed after being bitten by a pit viper, leading to a search for a blood pressure lowering component in its venom.<ref name="Aung2012">Template:Cite book</ref> Brazilian scientist Sérgio Henrique Ferreira reported a bradykinin-potentiating factor (BPF) present in the venom of Bothrops jararaca, a South American pit viper, in 1965.<ref name="pmid14302350">Template:Cite journal</ref> Ferreira then went to John Vane's laboratory as a postdoctoral fellow with his already-isolated BPF. The conversion of the inactive angiotensin I to the potent angiotensin II was thought to take place in the plasma. However, in 1967, Kevin K. F. Ng and John R. Vane showed plasma ACE is too slow to account for the conversion of angiotensin I to angiotensin II in vivo. Subsequent investigation showed rapid conversion occurs during its passage through the pulmonary circulation.<ref name="Kevin">Template:Cite journal</ref>

Bradykinin is rapidly inactivated in the circulating blood, and it disappears completely in a single pass through the pulmonary circulation. Angiotensin I also disappears in the pulmonary circulation because of its conversion to angiotensin II. Furthermore, angiotensin II passes through the lungs without any loss. The inactivation of bradykinin and the conversion of angiotensin I to angiotensin II in the lungs was thought to be caused by the same enzyme.<ref name="Kevin2">Template:Cite journal</ref> In 1970, Ng and Vane, using BPF provided by Ferreira, showed the conversion is inhibited during its passage through the pulmonary circulation.<ref name="Kevin3">Template:Cite journal</ref>

BPFs are members of a family of peptides whose potentiating action is linked to inhibition of bradykinin by ACE. Molecular analysis of BPF yielded a nonapeptide BPF teprotide (SQ 20,881), which showed the greatest ACE inhibition potency and hypotensive effect in vivo. Teprotide had limited clinical value as a result of its peptide nature and lack of activity when given orally. In the early 1970s, knowledge of the structure-activity relationship required for inhibition of ACE was growing. David Cushman, Miguel Ondetti and colleagues used peptide analogues to study the structure of ACE, using carboxypeptidase A as a model. Their discoveries led to the development of captopril, the first orally-active ACE inhibitor, in 1975.<ref>Template:Cite journal</ref>

Captopril was approved by the United States Food and Drug Administration in 1981.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The first nonsulfhydryl-containing ACE inhibitor, enalapril, was approved four years later.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> At least 8 other ACE inhibitors have since been marketed.<ref>Template:Cite journal</ref>

In 1991, Japanese scientists created the first milk-based ACE inhibitor, in the form of a fermented milk drink, using specific cultures to liberate the tripeptide isoleucine-proline-proline (IPP) from the dairy protein. Valine-proline-proline (VPP) is also liberated in this process—another milk tripeptide with a very similar chemical structure to IPP. Together, these peptides are now often referred to as lactotripeptides. In 1996, the first human study confirmed the blood pressure-lowering effect of IPP in fermented milk.<ref>Template:Cite journal</ref> Although twice the amount of VPP is needed to achieve the same ACE-inhibiting activity as the originally discovered IPP, VPP also is assumed to add to the total blood pressure lowering effect.<ref name="pmid7673515">Template:Cite journal</ref> Since the first lactotripeptides discovery, more than 20 human clinical trials have been conducted in many different countries.<ref name="pmid19061526">Template:Cite journal</ref>

NoteEdit

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See alsoEdit

ReferencesEdit

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External linksEdit

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