Enalapril (10–20 μM) reduces DAD- and EAD-induced activity and shows antiarrhythmic effects in an ultrafiltered PV sleeve preparation isolated from canine heart [1]. Only when enalapril (50 μM, 24 h) is administered before treating HUVEC with Alzheimer's disease (AD) serum does it prevent patient serum-induced apoptosis [2]. The thermal stability of pure enalapril is superior to that of pure enalapril [3].

The infarct volume generated by middle cerebral artery occlusion can be reduced by enalapril (intraperitoneal injection, 0.03 mg/kg, once, 1 hour), though neither lower nor higher dosages are beneficial in male NMRI mice [4].

Apoptosis analysis [2]
Cell Types: Human umbilical vein EC (HUVEC)
Tested Concentrations: 50 μM
Incubation Duration: 24 hrs (hours)
Experimental Results: Inhibition of apoptosis induced by patient serum.

Animal/Disease Models: Male NMRI mice 20-40 g [4]
Doses: 0.03 mg/kg
Route of Administration: intraperitoneal (ip) injection; one-time
Experimental Results:0.03 mg/kg can reduce the infarct area of the middle cerebral artery in mice.

Absorption, Distribution and Excretion
Following oral administration, peak plasma concentration (Cmax) of enalapril is reached within 1 hour of administration, while that of enalapril is reached 3 to 4 hours after administration. Steady-state plasma concentrations are achieved with a fourth daily dose, and repeated dosing does not lead to drug accumulation. However, patients with creatinine clearance below 30 mL/min may experience enalapril accumulation. Food intake has been reported to have little effect on drug absorption. Approximately 60% of enalapril is absorbed after oral administration. The mean bioavailability of enalapril is approximately 40% compared to intravenous enalapril. Enalapril is primarily excreted via the kidneys, with approximately 94% of the total dose excreted in urine or feces as enalapril or unchanged drug. Approximately 61% and 33% of the total dose are recovered in urine and feces, respectively. In urine, approximately 40% of the recovered dose is enalapril. The volume of distribution of enalapril has not been determined. Enalapril can penetrate most tissues, especially the kidneys and blood vessels, but its ability to cross the blood-brain barrier at therapeutic doses has not been confirmed. In canine studies, enalapril and enalapril-ladenine have poor ability to cross the blood-brain barrier. Very little of the drug enters milk, but it is significantly transported via the fetal route. The drug can cross the placental barrier in rats and hamsters. Renal clearance in healthy male volunteers after oral administration is approximately 158 ± 47 mL/min. It has been reported that enalapril and enalapril-ladenine are undetectable in plasma 4 hours after administration. This study analyzed the pharmacokinetics and pharmacodynamics of enalapril administered intravenously at 0.50 mg/kg, orally as a placebo, and orally at three different doses (0.50, 1.00, and 2.00 mg/kg) in seven healthy horses. Serum concentrations of enalapril and enalapril-ladenine were measured for pharmacokinetic analysis. Pharmacodynamic analysis was performed by measuring angiotensin-converting enzyme (ACE) activity, serum blood urea nitrogen (SUN), creatinine, and electrolyte levels, and monitoring blood pressure. Following intravenous administration of enalapril, the elimination half-lives of enalapril and enalaprilat were 0.67 hours and 2.76 hours, respectively. After oral administration of enalapril, all horses had enalapril concentrations below the limit of quantitation (10 ng/mL), and 4 out of 7 horses had enalaprilat concentrations below the limit of quantitation. The mean angiotensin-converting enzyme (ACE) inhibition rates after intravenous administration of 0.50 mg/kg enalapril, placebo, and oral administration of 0.50, 1.00, and 2.00 mg/kg enalapril were 88.38%, 3.24%, 21.69%, 26.11%, and 30.19%, respectively. Blood pressure, SUN, creatinine, and electrolyte levels remained constant throughout the experiment. Unlike enalapril, enalapril maleate is well absorbed after oral administration. Although enalapril is a more potent angiotensin-converting enzyme inhibitor than enalapril, its high polarity results in low gastrointestinal absorption, with only about 3-12% of the oral dose being absorbed. In healthy individuals and hypertensive patients, approximately 55-75% of the oral dose of enalapril maleate is rapidly absorbed by the gastrointestinal tract. Food does not appear to significantly affect the rate or extent of enalapril maleate absorption. After oral administration, enalapril maleate undergoes first-pass metabolism primarily in the liver, hydrolyzing into enalapril. Following a single oral dose of enalapril maleate, its antihypertensive effect typically appears within 1 hour and peaks within 4-8 hours. The antihypertensive effect at commonly used doses usually lasts 12-24 hours, but in some patients, the effect may diminish at the end of the dosing interval. Blood pressure reduction may be a gradual process, requiring several weeks of treatment to achieve full efficacy.
After intravenous injection of enalapril, the antihypertensive effect is usually observed within 5-15 minutes and reaches its maximum effect within 1-4 hours; the duration of the antihypertensive effect appears to be dose-related, but at the recommended dose, the duration of the antihypertensive effect is approximately 6 hours in most patients. Inhibition of plasma angiotensin-converting enzyme (ACE) and a decrease in blood pressure appear to be associated with plasma enalapril concentrations reaching 10 ng/mL, which achieves maximum blocking effect on plasma ACE. Blood pressure gradually returns to pre-treatment levels after discontinuation of enalapril or enalapril; to date, there have been no reports of rebound hypertension following abrupt discontinuation. Enalapril/
For more complete data on the absorption, distribution, and excretion of enalapril (11 in total), please visit the HSDB records page.

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Metabolism/Metabolites
Approximately 60% of the absorbed dose is extensively hydrolyzed to enalapril via hepatic esterase-mediated deesterification. No further metabolism after bioactivation to enalapril has been observed in humans. Approximately 60% of the absorbed dose of enalapril is extensively hydrolyzed to enalaprilat primarily in the liver by esterases. About 20% appears to be hydrolyzed during the first pass through the liver; this hydrolysis does not appear to occur in human plasma. Enalaprilat is a more potent angiotensin-converting enzyme inhibitor than enalapril. There is no evidence of other metabolites of enalapril in humans, rats, or dogs. However, the depropanol metabolite of enalaprilat has been detected in the urine of rhesus monkeys, representing 13% of the oral dose of enalapril maleate. In patients with severe hepatic impairment, the hydrolysis of enalapril to enalaprilat may be delayed and/or impaired, but the pharmacodynamic effects of the drug do not appear to be significantly altered.

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Biological Half-Life
The mean terminal half-life of enalaprilat is 35–38 hours. The effective half-life after multiple doses is 11–14 hours. The prolonged terminal half-life is due to the binding of enalapril to angiotensin-converting enzyme (ACE). After oral administration, the half-life of unmetabolized enalapril appears to be less than 2 hours in healthy individuals and patients with normal hepatic and renal function, but it may be prolonged in patients with congestive heart failure. In patients with congestive heart failure, the half-lives of enalapril after a single oral dose of 5 or 10 mg of enalapril maleate are 3.4 hours and 5.8 hours, respectively. The elimination of enalapril may also be prolonged in patients with congestive heart failure or impaired hepatic function compared to healthy individuals and hypertensive patients. Long-term observation of serum enalapril concentrations after oral or intravenous administration suggests that the mean terminal half-life of enalapril is approximately 35–38 hours (range: 30–87 hours). …It has been reported that in healthy individuals with normal renal function, the mean effective accumulation half-life of enalapril (measured based on urinary recovery) is approximately 11 hours.

Hepatotoxicity
Enalapril, like other ACE inhibitors, is associated with a low incidence of elevated serum transaminases (Probability Score: B (likely, but rarely, to cause clinically significant liver injury)). Pregnancy and Lactation Effects ◉ Overview of Use During Lactation Due to the low levels of enalapril in breast milk, the amount ingested by infants is minimal, and no adverse effects are expected on breastfed infants. ◉ Effects on Breastfed Infants No adverse reactions were reported in breastfed infants of 4 mothers who took enalapril 5 to 10 mg daily. ◉ Effects on Lactation and Breast Milk In 15 postmenopausal women with hypertension (no prior lactation status specified), serum prolactin levels were reduced by 22% compared to placebo. After taking enalapril 20 mg once daily for 15 days, prolactin levels in established lactating mothers are unlikely to affect their ability to breastfeed. A woman with preeclampsia was treated with enalapril 10 mg once daily at full term. She began lactating on day 3 postpartum and breastfed without difficulty during a 5-week observation period. Protein Binding: Based on limited data from studies on enalapril binding in human plasma (including balanced dialysis and ultrafiltration), enalapril reportedly binds to human plasma proteins at a rate of less than 50%.

[1]. Antiarrhythmic effects of losartan and enalapril in canine pulmonary vein sleeve preparations. J Cardiovasc Electrophysiol. 2011 Jun;22(6):698-705.

[2]. Enalapril protects endothelial cells against induced apoptosis in Alzheimer's disease. J Res Med Sci. 2013 Mar;18(Suppl 1):S1-5.

[3]. Effect of stearic acid on enalapril stability and dissolution from multiparticulate solid dosage forms. AAPS PharmSciTech. 2013 Sep;14(3):1150-7.

[4]. Enalapril and moexipril protect from free radical-induced neuronal damage in vitro and reduce ischemic brain injury in mice and rats. Eur J Pharmacol. 1999 May 28;373(1):21-33.

Enalapril is a dicarboxylic acid monoester, chemically named ethyl 4-phenylbutyrate, in which the hydrogen at the α-position of the carboxyl group is replaced by the amino group of L-alanyl-L-proline (S-configuration). It is a prodrug, belonging to EC 3.4.15.1 (peptidyl dipeptidase A) inhibitors, and possesses antihypertensive and anti-aging effects. It is a dicarboxylic acid monoester and dipeptide. Its function is related to anhydrous enalapril. Enalapril is an angiotensin-converting enzyme (ACE) inhibitor prodrug that acts on the renin-angiotensin-aldosterone system, which is responsible for regulating blood pressure and fluid and electrolyte balance. Enalapril is an orally effective, long-acting, non-sulfhydryl antihypertensive drug that lowers blood pressure by inhibiting the renin-angiotensin-aldosterone system. Enalapril was developed using targeted studies employing molecular modeling techniques. As a prodrug, enalapril is rapidly bioconverted into its active metabolite, enalapril, which is the active ingredient responsible for its pharmacological effects. Enalapril's active metabolite blocks the production of angiotensin II by competitively inhibiting angiotensin-converting enzyme (ACE). Angiotensin II is a key component of the renin-angiotensin-aldosterone system, promoting vasoconstriction and renal reabsorption of sodium ions. Ultimately, enalapril lowers blood pressure and blood volume. Enalapril (brand name: Vasotec) was first approved by the U.S. Food and Drug Administration (FDA) in 1985 for the treatment of hypertension, heart failure, and asymptomatic left ventricular dysfunction. It is also found in a combination formulation containing hydrochlorothiazide for the treatment of hypertension. Its active metabolite, enalapril, is available in both oral tablets and injectable formulations. Enalapril is an angiotensin-converting enzyme inhibitor. Its mechanism of action is as an angiotensin-converting enzyme inhibitor. Enalapril's physiological effect is achieved by lowering blood pressure. Enalapril is an angiotensin-converting enzyme (ACE) inhibitor widely used to treat hypertension and heart failure. Transient elevation of serum transaminases caused by enalapril is rare but has been associated with rare cases of acute liver injury. Enalapril is a dicarboxylic acid peptide drug and an angiotensin-converting enzyme (ACE) inhibitor with antihypertensive effects. Enalapril, as a prodrug, is deesterified to its active form, enalaprilat. Enalaprilat competitively binds to and inhibits ACE, thereby blocking the conversion of angiotensin I to angiotensin II. This prevents the potent vasoconstrictive effect of angiotensin II, leading to vasodilation. Enalapril also reduces adrenal cortical aldosterone secretion from angiotensin II, thereby increasing sodium excretion and consequently increasing water excretion. An angiotensin-converting enzyme inhibitor used to treat hypertension and heart failure. See also: Enalaprilat (note moved to).

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Drug Indications
Indications for the treatment of essential hypertension or renovascular hypertension, as monotherapy or in combination with other antihypertensive drugs (such as thiazide diuretics) for additive therapeutic effects. Indications for the treatment of symptomatic congestive heart failure, usually in combination with diuretics and digitalis. Indications for the treatment of asymptomatic left ventricular dysfunction with an ejection fraction ≤35% to reduce the incidence of overt heart failure and hospitalization for heart failure.
FDA Label
Mechanism of Action
The renin-angiotensin-aldosterone system (RAAS) is a signaling pathway that works synergistically with the sympathetic nervous system to regulate blood pressure and fluid and electrolyte balance. This system is activated by various stimuli such as hypotension and nerve impulses, leading to the release of more norepinephrine (NE) from sympathetic nerve endings and affecting angiogenesis, vasoconstriction, and renal sodium retention. Renin is released from renin and acts on the precursor protein angiotensinogen (a plasma globulin synthesized by the liver) to generate the cleaved peptide hormone angiotensin I. Angiotensin I can then be further cleaved by angiotensin-converting enzyme (ACE) to generate angiotensin II, a vasoconstrictive peptide hormone. Angiotensin-converting enzyme (ACE) is a peptidyl dipeptidase that exists in various isoenzyme forms and is expressed in a variety of tissues, including vascular tissues such as the heart, brain, and kidneys. ACE is also involved in the inactivation of bradykinin (a potent vasodilator peptide). Angiotensin II mediates a variety of effects on the body by acting on its G protein-coupled receptors AT1 and AT2. It directly causes vasoconstriction in precapillary arterioles and postcapillary venules, inhibits the reabsorption of norepinephrine (NE) thereby increasing its availability, stimulates the release of catecholamines from the adrenal medulla, reduces urinary sodium and water excretion by promoting proximal tubular reabsorption, stimulates the synthesis and release of aldosterone from the adrenal cortex, and stimulates hypertrophy of vascular smooth muscle cells and cardiomyocytes. Enalapril is a pharmacologically inactive prodrug that requires hepatic biotransformation to form its active metabolite [enalaprilat], which acts on the renin-angiotensin-aldosterone system (RAAS) to inhibit angiotensin-converting enzyme (ACE). Biotransformation is crucial for the therapeutic effect of this drug because enalapril itself is only a weak ACE inhibitor. ACE inhibitors reduce the production and plasma levels of angiotensin II, leading to increased plasma renin activity and reduced aldosterone secretion due to the loss of angiotensin II feedback inhibition. However, plasma aldosterone levels usually return to normal after long-term use of enalapril. Decreased angiotensin II levels subsequently lead to peripheral vasodilation and reduced vascular resistance, thereby lowering blood pressure. Although inhibition of ACE, and consequently the renin-angiotensin-aldosterone system (RAAS), is considered the primary mechanism of action for enalapril, studies have shown that the drug still has an antihypertensive effect in patients with low renin-induced hypertension. This suggests that enalapril may exert its pharmacological effects through other, not yet fully elucidated, mechanisms of action. Since the structure of ACE is similar to kallikrein I (a carboxypeptidase that degrades bradykinin), whether elevated bradykinin levels play a role in the therapeutic effect of enalapril remains to be elucidated. Enalapril maleate is a prodrug of enalapril and has almost no pharmacological activity before being hydrolyzed to enalapril in vivo. …Enalapril prevents the conversion of angiotensin I to angiotensin II (a potent vasoconstrictor) by inhibiting angiotensin-converting enzyme (ACE). This drug competes with the physiological substrate (angiotensin I) for the active site of ACE; enalapril has an affinity for angiotensin-converting enzyme (ACE) that is approximately 200,000 times higher than that of angiotensin I. In vitro experiments showed that enalapril's affinity for ACE (in molar concentration) was 300-1000 times that of enalapril and 2-17 times that of captopril. However, in vitro experiments showed that enalapril's ACE inhibitory effect in rat plasma and kidney was similar to that of enalapril, because these tissues extensively hydrolyze enalapril to generate enalapril. The drug does not appear to inhibit ACE in the animal brain.

C20H28N2O5

376.45

376.199

75847-73-3

Enalapril maleate;76095-16-4;Enalapril-d5 maleate;349554-02-5;Enalapril sodium;149404-21-7

5388962

White to off-white solid powder

1.2±0.1 g/cm3

582.3±50.0 °C at 760 mmHg

143-144.5ºC

306.0±30.1 °C

0.0±1.7 mmHg at 25°C

1.550

2.43

2

6

10

27

519

3

O=C(O)[C@H]1N(C([C@H](C)N[C@H](C(OCC)=O)CCC2=CC=CC=C2)=O)CCC1

GBXSMTUPTTWBMN-XIRDDKMYSA-N

InChI=1S/C20H28N2O5/c1-3-27-20(26)16(12-11-15-8-5-4-6-9-15)21-14(2)18(23)22-13-7-10-17(22)19(24)25/h4-6,8-9,14,16-17,21H,3,7,10-13H2,1-2H3,(H,24,25)/t14-,16-,17-/m0/s1

((S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl)-L-alanyl-L-proline

Kinfil Bonuten Enalapril Gadopril

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)