Question

Angiotensin-converting enzyme (ACE) inhibitor drug enalaprilat is used to treat hypertension and has poor oral bioavailability as well as a short half-life. What functional groups and properties of the drug may be responsible for these drawbacks and what can be done to modify the structure to improve both oral bioavailability and half-life?

Answer 1

Description:

Enalapril is a dicarbocyl-containing peptide and angiotensin-converting enzyme (ACE) inhibitor with antihypertensive activity. As a prodrug, enalapril is converted by de-esterification into 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 actions of angiotensin II and results in vasodilation. Enalapril also decreases angiotensin II-induced aldosterone secretion by the adrenal cortex, which leads to an increase in sodium excretion and subsequently increases water outflow.

Enalapril is an angiotensin-converting enzyme (ACE) inhibitor widely used in the therapy of hypertension and heart failure. Enalapril is associated with a low rate of transient serum aminotransferase elevations and has been linked to rare instances of acute liver injury. It is a dicarboxylic acid monoester that is ethyl 4-phenylbutanoate in which a hydrogen alpha to the carboxy group is substituted by the amino group of L-alanyl-L-proline (S-configuration). It has a role as a prodrug, an EC 3.4.15.1 (peptidyl-dipeptidase A) inhibitor and an antihypertensive agent. It is a dicarboxylic acid monoester and a dipeptide. It derives from an enalaprilat (anhydrous).

As Enalaprilat is a potent and reversible inhibitor of the plasma and tissue angiotensin-converting enzyme (ACE); it is used clinically in the treatment of hypertension . Although enalaprilat has potent and prompt therapeutic activity when administered intravenously, its high polarity and transport characteristics cause it to be poorly absorbed from the gastrointestinal tract. This leads to extremely low bioavailability of enalaprilat when administered orally.The effective accumulation half-life following multiple dosing is 11 hours. Higher serum concentrations and delayed urinary excretion occur in patients with severe renal insufficiency. Enalapril reduces blood pressure in hypertensive patients by decreasing systemic vascular resistance.

The effective half-life for accumulation of enalaprilat following multiple doses of enalapril maleate is 11 hours. The disposition of enalapril and enalaprilat in patients with renal insufficiency is similar to that in patients with normal renal function until the glomerular filtration rate is 30 mL/min or less. With glomerular filtration rate ≤30 mL/min, peak and trough enalaprilat levels increase, time to peak concentration increases and time to steady state may be delayed. The effective half-life of enalaprilat following multiple doses of enalapril maleate is prolonged at this level of renal insufficiency