Quinapril

Absorption

Quinapril if 50-80% bioavailable. Quinapril has a Tmax of <1 hour, while quinaprilat has a Tmax of 2.5h. The Cmax of quinaprilat is highly variable but reaches 1526ng/mL with an AUC of 2443ng*h/mL in healthy males given a 10mg dose. A high fat meal reduces the absorption of quinapril by 25-30%.

Toxicity

The oral LD50 in rats is 3541mg/kg and in mice is 1739mg/kg.
Patients experiencing an overdose may present with symptoms of severe hypotension. Due to the extensive protein binding of quinapril and the active metabolite quinaprilat, hemodialysis is not expected to remove the drug from circulation. Treat patients with symptomatic and supportive measures, including normal saline infusions to restore normal blood pressure.

Description

Quinapril is an orally active, non-sulfhydryl ACE inhibitor reportedly useful in the treatment of essential hypertension. The main claimed advantage of quinapril compared with other available ACE inhibitors is its side-effect profile. It is also effective in the management of congestive heart failure.

Originator

Warner-Lambert (USA)

The Uses of Quinapril

Antihypertensive; enzyme inhibitor (angiotensin-converting).

Indications

Quinapril is indicated for the treatment of hypertension and as an adjunct therapy in the treatment of heart failure. Quinapril in combination with hydrochlorothiazide is indicated for the treatment of hypertension.

Background

Quinapril is the ethyl ester prodrug of the non-sulfhydryl angiotensin converting enzyme inhibitor quinaprilat. It is used to treat hypertension and heart failure. ACE inhibitors are commonly used as a first line therapy in the treatment of hypertension, along with thiazide diuretics or beta blockers.
Quinapril was granted FDA approval on 19 November 1991. A combination tablet with hydrochlorothiazide was also approved on 28 December 1999.

Definition

ChEBI: Quinapril is a member of the class of isoquinolines that is (3S)-2-L-alanyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid in which the alpha-amino group of the alanyl residue has been substituted by a 1-ethoxycarbonyl-4-phenylbutan-2-yl group (the all-S isomer). A prodrug for quinaprilat (by hydrolysis of the ethyl ester to the corresponding carboxylic acid), it is used as an angiotensin-converting enzyme inhibitor (ACE inhibitor) used (generally as the hydrochloride salt) for the treatment of hypertension and congestive heart failure. It has a role as an EC 3.4.15.1 (peptidyl-dipeptidase A) inhibitor, a prodrug and an antihypertensive agent. It is a member of isoquinolines, a dicarboxylic acid monoester, an ethyl ester and a tertiary carboxamide.

brand name

Accupril (Pfizer); Quinapril (Lupin); Quinapril (Ranbaxy) ;Accupro.

Pharmacokinetics

Quinapril is a prodrug of an angiotensin converting enzyme (ACE) inhibitor used in the treatment of hypertension or adjunct in the treatment of heart failure. Quinapril has a wide therapeutic window and a long duration of action as it is given in doses of 10-80mg once daily.

Clinical Use

Angiotensin converting enzyme inhibitor:
Hypertension
Congestive heart failure

Drug interactions

Potentially hazardous interactions with other drugs
Anaesthetics: enhanced hypotensive effect.
Analgesics: antagonism of hypotensive effect and increased risk of renal impairment with NSAIDs; hyperkalaemia with ketorolac and other NSAIDs.
Antihypertensives: increased risk of hyperkalaemia, hypotension and renal failure with ARBs and aliskiren.
Bee venom extract: possible severe anaphylactoid reactions when used together.
Ciclosporin: increased risk of hyperkalaemia and nephrotoxicity.
Cytotoxics: increased risk of angioedema with everolimus.
Diuretics: enhanced hypotensive effect; hyperkalaemia with potassium-sparing diuretics.
ESAs: increased risk of hyperkalaemia; antagonism of hypotensive effect.
Gold: flushing and hypotension with sodium aurothiomalate.
Lithium: reduced excretion (possibility of enhanced lithium toxicity).
Potassium salts: increased risk of hyperkalaemia.
Tacrolimus: increased risk of hyperkalaemia and nephrotoxicity.

Metabolism

Quinapril is de-esterified to the active quinaprilat or dehydrated to form the inactive PD109488. PD109488 can undergo O-deethylation to form another inactive metabolite, PD113413.

Metabolism

Quniapril is a prodrug which is metabolised in the liver to its active form, quinaprilat, and to minor inactive metabolites.
Quinaprilat is eliminated primarily by renal excretion.