Molecule

Drug Groups

approved

Description

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.

Indication

For the treatment of mild to moderate hypertension, as an adjunct in the treatment of congestive heart failure (CHF), to improve survival following myocardial infarction (MI) in individuals who are hemodynamically stable and demonstrate symptoms of left ventricular systolic dysfunction or signs of CHF within a few days following acute MI, and to slow progression of renal disease in hypertensive patients with diabetes mellitus and microalbuminuria or overt nephropathy.

Pharmacology

Trandolapril is the ethyl ester prodrug of a nonsulfhydryl ACE inhibitor, trandolaprilat. Trandolapril is deesterified in the liver to the diacid metabolite, trandolaprilat, which is approximately eight times more active as an inhibitor of ACE than its parent compound. ACE is a peptidyl dipeptidase that is part of the RAAS. The 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 the granular cells of the juxtaglomerular apparatus in the kidneys. In the blood stream, renin cleaves circulating angiotensinogen to ATI, which is subsequently cleaved to ATII by ACE. ATII increases blood pressure via a number of mechanisms. First, it stimulates the secretion of aldosterone from the adrenal cortex. Aldosterone travels to the distal convoluted tubule (DCT) and collecting tubule of nephrons where it increases sodium and water reabsorption by increasing the number of sodium channels and sodium-potassium ATPases on cell membranes. Second, ATII stimulates the secretion of vasopressin (also known as antidiuretic hormone or ADH) from the posterior pituitary gland. ADH stimulates further water reabsorption from the kidneys via insertion of aquaporin-2 channels on the apical surface of cells of the DCT and collecting tubules. Third, ATII increases blood pressure through direct arterial vasoconstriction. Stimulation of the Type 1 ATII receptor on vascular smooth muscle cells leads to a cascade of events resulting in myocyte contraction and vasoconstriction. In addition to these major effects, ATII induces the thirst response via stimulation of hypothalamic neurons. ACE inhibitors inhibit the rapid conversion of ATI to ATII and antagonize RAAS-induced increases in blood pressure. ACE (also known as kininase II) is also involved in the enzymatic deactivation of bradykinin, a vasodilator. Inhibiting the deactivation of bradykinin increases bradykinin levels and may further sustain the effects of trandolaprilat by causing increased vasodilation and decreased blood pressure. The blood pressure lowering effect of trandolaprilat is due to a decrease in peripheral vascular resistance, which is not accompanied by significant changes in urinary excretion of chloride or potassium or water or sodium retention.

Toxicity

Most likely clinical manifestations of overdose are symptoms of severe hypotension. Most common adverse effects include cough, headache and dizziness. The oral LD₅₀ of trandolapril in mice was 4875 mg/kg in males and 3990 mg/kg in females. In rats, an oral dose of 5000 mg/kg caused low mortality (1 male out of 5; 0 females). In dogs, an oral dose of 1000 mg/kg did not cause mortality and abnormal clinical signs were not observed.

Affected Organisms

Biotransformation

Cleavage of the ester group of trandolapril, primarily in the liver, is responsible for conversion to trandolaprilat, the active metabolite. Seven other metabolites, including diketopiperazine and glucuronide conjugated derivatives of trandolapril and trandolaprilat, have been identified.

Absorption

~ 40-60% absorbed; extensive first pass metabolism results in a low bioavailability of 4-14%

Half Life

The elimination half lives of trandolapril and trandolaprilat are about 6 and 10 hours, respectively, but, similar to all ACE inhibitors, trandolaprilat also has a prolonged terminal elimination phase that involves a small fraction of administered drug. This likely represents drug binding to plasma and tissue ACE. The effective half life of elimination for trandolaprilat is 16-24 hours.

Protein Binding

Serum protein binding of trandolapril is ~ 80% (independent of concentration and not saturable) while that of trandolaprilat is 65 to 94% (concentration-dependent and saturable).

Elimination

After oral administration of trandolapril, about 33% of parent drug and metabolites are recovered in urine, mostly as trandolaprilat, with about 66% in feces.

Distribution

* 18 L

Clearance

* 52 L/h [After approximately 2 mg IV doses]

References

External Links