CLINICAL PHARMACOLOGY
Mechanism Of Action
Trandolapril is deesterified to the diacid metabolite,
trandolaprilat, which is approximately eight times more active as an inhibitor
of ACE activity. ACE is a peptidyl dipeptidase that catalyzes the conversion of
angiotensin I to the vasoconstrictor, angiotensin II. Angiotensin II is a
potent peripheral vasoconstrictor that also stimulates secretion of aldosterone
by the adrenal cortex and provides negative feedback for renin secretion. The
effect of trandolapril in hypertension appears to result primarily from the
inhibition of circulating and tissue ACE activity thereby reducing angiotensin
II formation, decreasing vasoconstriction, decreasing aldosterone secretion,
and increasing plasma renin. Decreased aldosterone secretion leads to diuresis,
natriuresis, and a small increase of serum potassium. In controlled clinical
trials, treatment with MAVIK alone resulted in mean increases in potassium of
0.1 mEq/L. (see PRECAUTIONS.)
ACE is identical to kininase II, an enzyme that degrades
bradykinin, a potent peptide vasodilator; whether increased levels of
bradykinin play a role in the therapeutic effect of trandolapril remains to be
elucidated.
While the principal mechanism of antihypertensive effect
is thought to be through the reninangiotensin-aldosterone system, trandolapril
exerts antihypertensive actions even in patients with low-renin hypertension.
MAVIK was an effective antihypertensive in all races studied. Both black
patients (usually a predominantly low-renin group) and non-black patients
responded to 2 to 4 mg of MAVIK.
Pharmacokinetics And Metabolism
Pharmacokinetics
Trandolapril's ACE-inhibiting activity is primarily due
to its diacid metabolite, trandolaprilat. Cleavage of the ester group of
trandolapril, primarily in the liver, is responsible for conversion. Absolute
bioavailability after oral administration of trandolapril is about 10% as
trandolapril and 70% as trandolaprilat. After oral trandolapril under fasting
conditions, peak trandolapril levels occur at about one hour and peak
trandolaprilat levels occur between 4 and 10 hours. The elimination half-life
of trandolapril is about 6 hours. At steady state, the effective half-life of
trandolaprilat is 22.5 hours. Like all ACE inhibitors, trandolaprilat also has
a prolonged terminal elimination phase, involving a small fraction of
administered drug, probably representing binding to plasma and tissue ACE. During
multiple dosing of trandolapril, there is no significant accumulation of
trandolaprilat. Food slows absorption of trandolapril, but does not affect AUC
or Cmax of trandolaprilat or Cmax of trandolapril.
Metabolism And Excretion
After oral administration of trandolapril, about 33% of
parent drug and metabolites are recovered in urine, mostly as trandolaprilat,
with about 66% in feces. The extent of the absorbed dose which is biliary
excreted has not been determined. Plasma concentrations (Cmax and AUC of
trandolapril and Cmax of trandolaprilat) are dose proportional over the 1-4 mg
range, but the AUC of trandolaprilat is somewhat less than dose proportional.
In addition to trandolaprilat, at least 7 other metabolites have been found,
principally glucuronides or deesterification products.
Serum protein binding of trandolapril is about 80%, and
is independent of concentration. Binding of trandolaprilat is
concentration-dependent, varying from 65% at 1000 ng/mL to 94% at 0.1 ng/mL,
indicating saturation of binding with increasing concentration.
The volume of distribution of trandolapril is about 18
liters. Total plasma clearances of trandolapril and trandolaprilat after
approximately 2 mg IV doses are about 52 liters/hour and 7 liters/hour
respectively. Renal clearance of trandolaprilat varies from 1-4 liters/hour,
depending on dose.
Special Populations
Pediatric
Trandolapril pharmacokinetics have not been evaluated in
patients < 18 years of age.
Geriatric And Gender
Trandolapril pharmacokinetics have been investigated in
the elderly (> 65 years) and in both genders. The plasma concentration of
trandolapril is increased in elderly hypertensive patients, but the plasma
concentration of trandolaprilat and inhibition of ACE activity are similar in
elderly and young hypertensive patients. The pharmacokinetics of trandolapril
and trandolaprilat and inhibition of ACE activity are similar in male and
female elderly hypertensive patients.
Race
Pharmacokinetic differences have not been evaluated in
different races.
Renal Insufficiency
Compared to normal subjects, the plasma concentrations of
trandolapril and trandolaprilat are approximately 2-fold greater and renal
clearance is reduced by about 85% in patients with creatinine clearance below
30 ml/min and in patients on hemodialysis. Dosage adjustment is recommended in
renally impaired patients. (see DOSAGE AND ADMINISTRATION.)
Hepatic Insufficiency
Following oral administration in patients with mild to
moderate alcoholic cirrhosis, plasma concentrations of trandolapril and
trandolaprilat were, respectively, 9-fold and 2-fold greater than in normal
subjects, but inhibition of ACE activity was not affected. Lower doses should
be considered in patients with hepatic insufficiency. (see DOSAGE AND
ADMINISTRATION.)
Drug Interactions
Trandolapril did not affect the plasma concentration
(pre-dose and 2 hours post-dose) of oral digoxin (0.25 mg). Coadministration of
trandolapril and cimetidine led to an increase of about 44% in Cmax for
trandolapril, but no difference in the pharmacokinetics of trandolaprilat or in
ACE inhibition. Coadministration of trandolapril and furosemide led to an
increase of about 25% in the renal clearance of trandolaprilat, but no effect
was seen on the pharmacokinetics of furosemide or trandolaprilat or on ACE
inhibition.
Pharmacodynamics And Clinical Effects
A single 2-mg dose of MAVIK produces 70 to 85% inhibition
of plasma ACE activity at 4 hours with about 10% decline at 24 hours and about
half the effect manifest at 8 days. Maximum ACE inhibition is achieved with a
plasma trandolaprilat concentration of 2 ng/mL. ACE inhibition is a function of
trandolaprilat concentration, not trandolapril concentration. The effect of
trandolapril on exogenous angiotensin I was not measured.
Hypertension
Four placebo-controlled dose response studies were
conducted using once-daily oral dosing of MAVIK in doses from 0.25 to 16 mg per
day in 827 black and non-black patients with mild to moderate hypertension. The
minimal effective once-daily dose was 1 mg in non-black patients and 2 mg in
black patients. Further decreases in trough supine diastolic blood pressure
were obtained in non-black patients with higher doses, and no further response
was seen with doses above 4 mg (up to 16 mg). The antihypertensive effect
diminished somewhat at the end of the dosing interval, but trough/peak ratios
are well above 50% for all effective doses. There was a slightly greater effect
on the diastolic pressure, but no difference on systolic pressure with b.i.d.
dosing. During chronic therapy, the maximum reduction in blood pressure with
any dose is achieved within one week. Following 6 weeks of monotherapy in
placebo-controlled trials in patients with mild to moderate hypertension,
once-daily doses of 2 to 4 mg lowered supine or standing systolic/diastolic
blood pressure 24 hours after dosing by an average 7-10/4-5 mmHg below placebo
responses in non-black patients. Once-daily doses of 2 to 4 mg lowered blood
pressure 4-6/3-4 mmHg in black patients. Trough to peak ratios for effective
doses ranged from 0.5 to 0.9. There were no differences in response between men
and women, but responses were somewhat greater in patients under 60 than in
patients over 60 years old. Abrupt withdrawal of MAVIK has not been associated
with a rapid increase in blood pressure.
Administration of MAVIK to patients with mild to moderate
hypertension results in a reduction of supine, sitting and standing blood
pressure to about the same extent without compensatory tachycardia.
Symptomatic hypotension is infrequent, although it can
occur in patients who are salt-and/or volume-depleted. (see WARNINGS.)
Use of MAVIK in combination with thiazide diuretics gives a blood pressure
lowering effect greater than that seen with either agent alone, and the
additional effect of trandolapril is similar to the effect of monotherapy.
Heart Failure Post Myocardial Infarction Or Left
Ventricular Dysfunction Post Myocardial Infarction
The Trandolapril Cardiac Evaluation (TRACE) Trial was a
Danish, 27-center, double-blind, placebo controlled, parallel-group study of
the effect of trandolapril on all-cause mortality in stable patients with
echocardiographic evidence of left ventricular dysfunction 3 to 7 days after a
myocardial infarction. Subjects with residual ischemia or overt heart failure
were included. Patients tolerant of a test dose of 1 mg trandolapril were
randomized to placebo (n=873) or trandolapril (n=876) and followed for 24
months. Among patients randomized to trandolapril, who began treatment on 1 mg,
62% were successfully titrated to a target dose of 4 mg once daily over a period
of weeks. The use of trandolapril was associated with a 16% reduction in the
risk of all-cause mortality (p=0.042), largely cardiovascular mortality.
Trandolapril was also associated with a 20% reduction in the risk of
progression of heart failure (p=0.047), defined by a time-to-first-event
analysis of death attributed to heart failure, hospitalization for heart
failure, or requirement for open-label ACE inhibitor for the treatment of heart
failure. There was no significant effect of treatment on other end-points:
subsequent hospitalization, incidence of recurrent myocardial infarction,
exercise tolerance, ventricular function, ventricular dimensions, or NYHA class.
The population in TRACE was entirely Caucasian and had
less usage than would be typical in a U.S. population of other post-infarction
interventions: 42% thrombolysis, 16% beta-adrenergic blockade, and 6.7% PTCA or
CABG during the entire period of follow-up. Blood pressure control, especially
in the placebo group, was poor: 47 to 53% of patients randomized to placebo and
32 to 40% of patients randomized to trandolapril had blood pressures >
140/95 at 90-day follow-up visits.