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Zestril

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Zestril

CLINICAL PHARMACOLOGY

Mechanism Of Action

Lisinopril inhibits angiotensin-converting enzyme (ACE) in human subjects and animals. ACE is a peptidyl dipeptidase that catalyzes the conversion of angiotensin I to the vasoconstrictor substance, angiotensin II. Angiotensin II also stimulates aldosterone secretion by the adrenal cortex. The beneficial effects of lisinopril in hypertension and heart failure appear to result primarily from suppression of the renin-angiotensin-aldosterone system. Inhibition of ACE results in decreased plasma angiotensin II which leads to decreased vasopressor activity and to decreased aldosterone secretion. The latter decrease may result in a small increase of serum potassium. In hypertensive patients with normal renal function treated with Zestril alone for up to 24 weeks, the mean increase in serum potassium was approximately 0.1 mEq/L; however, approximately 15% of patients had increases greater than 0.5 mEq/L and approximately 6% had a decrease greater than 0.5 mEq/L. In the same study, patients treated with Zestril and hydrochlorothiazide for up to 24 weeks had a mean decrease in serum potassium of 0.1 mEq/L; approximately 4% of patients had increases greater than 0.5 mEq/L and approximately 12% had a decrease greater than 0.5 mEq/L [see Clinical Studies]. Removal of angiotensin II negative feedback on renin secretion leads to increased plasma renin activity.

ACE is identical to kininase, an enzyme that degrades bradykinin. Whether increased levels of bradykinin, a potent vasodepressor peptide, play a role in the therapeutic effects of Zestril remains to be elucidated.

While the mechanism through which Zestril lowers blood pressure is believed to be primarily suppression of the renin-angiotensin-aldosterone system, Zestril is antihypertensive even in patients with low-renin hypertension. Although Zestril was antihypertensive in all races studied, Black hypertensive patients (usually a low-renin hypertensive population) had a smaller average response to monotherapy than non Black patients.

Concomitant administration of Zestril and hydrochlorothiazide further reduced blood pressure in Black and non-Black patients and any racial differences in blood pressure response were no longer evident.

Pharmacodynamics

Hypertension

Adult Patients: Administration of Zestril to patients with hypertension results in a reduction of both supine and standing blood pressure to about the same extent with no compensatory tachycardia. Symptomatic postural hypotension is usually not observed although it can occur and should be anticipated in volume and/or salt-depleted patients [see WARNINGS AND PRECAUTIONS]. When given together with thiazide-type diuretics, the blood pressure lowering effects of the two drugs are approximately additive.

In most patients studied, onset of antihypertensive activity was seen at one hour after oral administration of an individual dose of Zestril, with peak reduction of blood pressure achieved by 6 hours. Although an antihypertensive effect was observed 24 hours after dosing with recommended single daily doses, the effect was more consistent and the mean effect was considerably larger in some studies with doses of 20 mg or more than with lower doses; however, at all doses studied, the mean antihypertensive effect was substantially smaller 24 hours after dosing than it was 6 hours after dosing.

The antihypertensive effects of Zestril are maintained during long-term therapy. Abrupt withdrawal of Zestril has not been associated with a rapid increase in blood pressure, or a significant increase in blood pressure compared to pretreatment levels.

Non-Steroidal Anti-Inflammatory Agents

In a study in 36 patients with mild to moderate hypertension where the antihypertensive effects of Zestril alone were compared to Zestril given concomitantly with indomethacin, the use of indomethacin was associated with a reduced effect, although the difference between the two regimens was not significant.

Pharmacokinetics

Adult Patients

Following oral administration of Zestril, peak serum concentrations of lisinopril occur within about 7 hours, although there was a trend to a small delay in time taken to reach peak serum concentrations in acute myocardial infarction patients. Food does not alter the bioavailability of Zestril. Declining serum concentrations exhibit a prolonged terminal phase, which does not contribute to drug accumulation. This terminal phase probably represents saturable binding to ACE and is not proportional to dose. Upon multiple dosing, lisinopril exhibits an effective half-life of 12 hours.

Lisinopril does not appear to be bound to other serum proteins. Lisinopril does not undergo metabolism and is excreted unchanged entirely in the urine. Based on urinary recovery, the mean extent of absorption of lisinopril is approximately 25%, with large intersubject variability (6-60%) at all doses tested (5-80 mg). The absolute bioavailability of lisinopril is reduced to 16% in patients with stable NYHA Class II-IV congestive heart failure, and the volume of distribution appears to be slightly smaller than that in normal subjects. The oral bioavailability of lisinopril in patients with acute myocardial infarction is similar to that in healthy volunteers.

Impaired renal function decreases elimination of lisinopril, which is excreted principally through the kidneys, but this decrease becomes clinically important only when the glomerular filtration rate is below 30 mL/min. Above this glomerular filtration rate, the elimination half-life is little changed. With greater impairment, however, peak and trough lisinopril levels increase, time to peak concentration increases and time to attain steady state is prolonged [see DOSAGE AND ADMINISTRATION]. Lisinopril can be removed by hemodialysis.

Pediatric Patients

The pharmacokinetics of lisinopril were studied in 29 pediatric hypertensive patients between 6 years and 16 years with glomerular filtration rate > 30 mL/min/1.73 m². After doses of 0.1 to 0.2 mg per kg, steady state peak plasma concentrations of lisinopril occurred within 6 hours and the extent of absorption based on urinary recovery was about 28%. These values are similar to those obtained previously in adults. The typical value of lisinopril oral clearance (systemic clearance/absolute bioavailability) in a child weighing 30 kg is 10 L/h, which increases in proportion to renal function.

Clinical Studies

Hypertension

Two dose-response studies utilizing a once-daily regimen were conducted in 438 mild to moderate hypertensive patients not on a diuretic. Blood pressure was measured 24 hours after dosing. An antihypertensive effect of Zestril was seen with 5 mg of Zestril in some patients. However, in both studies blood pressure reduction occurred sooner and was greater in patients treated with 10, 20 or 80 mg of Zestril than patients treated with 5 mg of Zestril.

In controlled clinical studies of patients with mild to moderate hypertension, patients were treated with Zestril 20-80 mg daily, hydrochlorothiazide 12.5-50 mg daily or atenolol 50-200 mg daily; and in other studies of patients with moderate to severe hypertension, patients were treated with Zestril 20-80 mg daily or metoprolol 100-200 mg daily. Zestril demonstrated superior reductions of systolic and diastolic compared to hydrochlorothiazide in a population that was 75% Caucasian. Zestril was approximately equivalent to atenolol and metoprolol in reducing diastolic blood pressure, and had somewhat greater effects on systolic blood pressure.

Zestril had similar blood pressure reductions and adverse effects in younger and older ( > 65 years) patients. It was less effective in reducing blood pressure in Blacks than in Caucasians.

In hemodynamic studies of Zestril in patients with essential hypertension, blood pressure reduction was accompanied by a reduction in peripheral arterial resistance with little or no change in cardiac output and in heart rate. In a study in nine hypertensive patients, following administration of Zestril, there was an increase in mean renal blood flow that was not significant. Data from several small studies are inconsistent with respect to the effect of lisinopril on glomerular filtration rate in hypertensive patients with normal renal function, but suggest that changes, if any, are not large.

In patients with renovascular hypertension Zestril has been shown to be well tolerated and effective in reducing blood pressure [see WARNINGS AND PRECAUTIONS].

Pediatric Patients

In a clinical study involving 115 hypertensive pediatric patients 6 to 16 years of age, patients who weighed < 50 kg received either 0.625, 2.5 or 20 mg of Zestril once daily and patients who weighed > 50 kg received either 1.25, 5, or 40 mg of Zestril once daily. At the end of 2 weeks, Zestril lowered trough blood pressure in a dose-dependent manner with antihypertensive efficacy demonstrated at doses > 1.25 mg (0.02 mg per kg). This effect was confirmed in a randomized withdrawal phase, where the diastolic pressure rose by about 9 mmHg more in patients randomized to placebo than compared to patients who remained on the middle and high doses of lisinopril. The dose-dependent antihypertensive effect of Zestril was consistent across several demographic subgroups: age, Tanner stage, gender, and race. In this study, lisinopril was generally well-tolerated.

In the above pediatric studies, Zestril was given either as tablets or in a suspension for those children and infants who were unable to swallow tablets or who required a lower dose than is available in tablet form [see DOSAGE AND ADMINISTRATION].

Heart Failure

In two placebo controlled, 12-week clinical studies compared the addition of Zestril up to 20 mg daily to digitalis and diuretics alone. The combination of Zestril, digitalis and diuretics reduced the following signs and symptoms of heart failure: edema, rales, paroxysmal nocturnal dyspnea and jugular venous distention. In one of the studies, the combination of Zestril, digitalis and diuretics reduced orthopnea, presence of third heart sound and the number of patients classified as NYHA Class III and IV; and improved exercise tolerance. A large (over 3000 patients) survival study, the ATLAS Trial, comparing 2.5 and 35 mg of lisinopril in patients with systolic heart failure, showed that the higher dose of lisinopril had outcomes at least as favorable as the lower dose.

During baseline-controlled clinical trials, in patients with systolic heart failure receiving digitalis and diuretics, single doses of Zestril resulted in decreases in pulmonary capillary wedge pressure, systemic vascular resistance and blood pressure accompanied by an increase in cardiac output and no change in heart rate.

Acute Myocardial Infarction

The Gruppo Italiano per lo Studio della Sopravvienza nell'Infarto Miocardico (GISSI-3) study was a multicenter, controlled, randomized, unblinded clinical trial conducted in 19,394 patients with acute myocardial infarction (MI) admitted to a coronary care unit. It was designed to examine the effects of short-term (6 week) treatment with lisinopril, nitrates, their combination, or no therapy on short-term (6 week) mortality and on long-term death and markedly impaired cardiac function. Hemodynamicallystable patients presenting within 24 hours of the onset of symptoms were randomized, in a 2 x 2 factorial design, to six weeks of either 1) Zestril alone (n=4841), 2) nitrates alone (n=4869), 3) Zestril plus nitrates (n=4841), or 4) open control (n=4843). All patients received routine therapies, including thrombolytics (72%), aspirin (84%), and a beta blocker (31%), as appropriate, normally utilized in acute myocardial infarction (MI) patients.

The protocol excluded patients with hypotension (systolic blood pressure < 100 mmHg), severe heart failure, cardiogenic shock, and renal dysfunction (serum creatinine > 2 mg per dL and/or proteinuria > 500 mg per 24 h). Patients randomized to Zestril received 5 mg within 24 hours of the onset of symptoms, 5 mg after 24 hours, and then 10 mg daily thereafter. Patients with systolic blood pressure less than 120 mmHg at baseline received 2.5 mg of Zestril. If hypotension occurred, the Zestril dose was reduced or if severe hypotension occurred Zestril was stopped [see DOSAGE AND ADMINISTRATION].

The primary outcomes of the trial were the overall mortality at 6 weeks and a combined end point at 6 months after the myocardial infarction, consisting of the number of patients who died, had late (day 4) clinical congestive heart failure, or had extensive left ventricular damage defined as ejection fraction < 35% or an akinetic-dyskinetic [A-D] score > 45%. Patients receiving Zestril (n=9646), alone or with nitrates, had an 11% lower risk of death (p=0.04) compared to patients who did not receive Zestril (n=9672) (6.4% vs. 7.2%, respectively) at six weeks. Although patients randomized to receive Zestril for up to six weeks also fared numerically better on the combined end point at 6 months, the open nature of the assessment of heart failure, substantial loss to follow-up echocardiography, and substantial excess use of Zestril between 6 weeks and 6 months in the group randomized to 6 weeks of lisinopril, preclude any conclusion about this end point.

Patients with acute myocardial infarction, treated with Zestril, had a higher (9.0% versus 3.7%) incidence of persistent hypotension (systolic blood pressure < 90 mmHg for more than 1 hour) and renal dysfunction (2.4% versus 1.1%) in-hospital and at six weeks (increasing creatinine concentration to over 3 mg per dL or a doubling or more of the baseline serum creatinine concentration) [see ADVERSE REACTIONS].

Last reviewed on RxList: 7/14/2014
This monograph has been modified to include the generic and brand name in many instances.

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