Prescription Drug Information: Lisinopril with Hydrochlorothiazide

LISINOPRIL WITH HYDROCHLOROTHIAZIDE — lisinopril and hydrochlorothiazide tablet
H.J. Harkins Company, Inc.

Rx Only

USE IN PREGNANCY

When used in pregnancy during the second and third trimesters, ACE inhibitors can cause injury and even death to the developing fetus. When pregnancy is detected, lisinopril and hydrochlorothiazide should be discontinued as soon as possible. See WARNINGS, Pregnancy Lisinopril, Fetal/Neonatal Morbidity and Mortality.

DESCRIPTION

Lisinopril and hydrochlorothiazide combines an angiotensin converting enzyme inhibitor, lisinopril and a diuretic, hydrochlorothiazide.

Lisinopril, a synthetic peptide derivative, is an oral long-acting angiotensin converting enzyme inhibitor. It is chemically described as (S)-1-[N 2 -(1-carboxy-3-phenylpropyl)L-lysyl]-L-proline dihydrate. Its empirical formula is C21 H31 N3 05 •2H2 0 and its structural formula is:

Structural Formula 1
(click image for full-size original)

Lisinopril is a white to off-white, crystalline powder, with a molecular weight of 441.52. It is soluble in water, sparingly soluble in methanol, and practically insoluble in ethanol.

Hydrochlorothiazide is 6-chloro-3,4-dihydro-2H -1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide. Its empirical formula is C7 H8 CIN3 04 S2 and its structural formula is:

Structural Formula 2

Hydrochlorothiazide is a white, or practically white, crystalline powder with a molecular weight of 297.73, which is slightly soluble in water, but freely soluble in sodium hydroxide solution.

Lisinopril and hydrochlorothiazide is available for oral use in three tablet combinations of lisinopril and hydrochlorothiazide: 10-12.5 mg containing 10 mg lisinopril and 12.5 mg hydrochlorothiazide, lisinopril and hydrochlorothiazide: 20-12.5 mg containing 20 mg lisinopril and 12.5 mg hydrochlorothiazide and lisinopril and hydrochlorothiazide: 20-25 mg containing 20 mg lisinopril and 25 mg hydrochlorothiazide.

Inactive ingredients are as follows:

10/12.5 mg: Calcium Phosphate Dibasic, Colloidal Silicon Dioxide, Corn Starch, FD&C Blue #2, Lactose Monohydrate, Magnesium Stearate, Mannitol, and Sodium Starch Glycolate.

20/12.5 mg: Calcium Phosphate Dibasic, Colloidal Silicon Dioxide, Corn Starch, Lactose Monohydrate, Magnesium Stearate, Mannitol, Sodium Starch Glycolate, and Yellow Iron Oxide.

20/25 mg: Calcium Phosphate Dibasic, Colloidal Silicon Dioxide, Corn Starch, Lactose Monohydrate, Magnesium Stearate, Mannitol, Red Iron Oxide, and Sodium Starch Glycolate.

CLINICAL PHARMACOLOGY

Lisinopril-Hydrochlorothiazide

As a result of its diuretic effects, hydrochlorothiazide increases plasma renin activity, increases aldosterone secretion, and decreases serum potassium. Administration of lisinopril blocks the renin-angiotensin-aldosterone axis and tends to reverse the potassium lose associated with the diuretic.

In clinical studies, the extent of blood pressure reduction seen with the combination of lisinopril and hydrochlorothiazide was approximately additive. The lisinopril and hydrochlorothiazide 10-12.5 mg combination worked equally well in black and white patients. The lisinopril and hydrochlorothiazide 20-12.5 mg and lisinopril and hydrochlorothiazide combinations appeared somewhat less effective in black patients, but relatively few black patients were studies. In most patients, the antihypertensive effect of lisinopril and hydrochlorothiazide was sustained for at least 24 hours.

In a randomized, controlled comparison, the mean antihypertensive effects of Lisinopril and Hydrochlorothiazide 20-12.5 mg and Lisinopril and Hydrochlorothiazide 20-25 mg were similar, suggesting that many patients who respond adequately to the latter combination may be controlled with Lisinopril and Hydrochlorothiazide 20-12.5 mg. (See DOSAGE AND ADMINISTRATION.)

Concomitant administration of lisinopril and hydrochlorothiazide has little or no effect on the bioavailability of either drug. The combination tablet is bioequivalent to concomitant administration of the separate entities.

Lisinopril

Mechanism of Action

Lisinopril inhibits angiotensin-converting enzyme (ACE) in human subjects and animals. ACE is 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. 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. Removal of angiotensin II negative feed-back on renin secretion leads to increased plasma renin activity. In hypertensive patients with normal renal function treated with lisinopril alone for up to 24 weeks, the mean increase in serum potassium was less than 0.1 mEq/L; however, approximately 15 percent of patients had increases greater than 0.5 mEq/L and approximately six percent had a decrease greater than 0.5 mEq/L. In the same study, patients treated with lisinopril plus a thiazide diuretic showed essentially no change in serum potassium (see PRECAUTIONS).

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 lisinopril remains to be elucidated.

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

Pharmacokinetics and Metabolism

Following oral administration of lisinopril, peak, serum concentrations occur within about 7 hours. 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. 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 percent, with large intersubject variability (6-60 percent) at all doses tested (5-80 mg). Lisinopril absorption is not influenced by the presence of food in the gastrointestinal tract.

Upon multiple dosing, lisinopril exhibits an effective half-life of accumulation of 12 hours.

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. Older patients, on average, have (approximately doubled) higher blood levels and area under the plasma concentration time curve (AUC) than younger patients. (See DOSAGE AND ADMINISTRATION.) Lisinopril can be removed by hemodialysis.

Studies in rats indicate that lisinopril crosses the blood-brain barrier poorly. Multiple doses of lisinopril in rats do not result in accumulation in any tissues. However, milk of lactating rats contains radioactivity following administration of 14 C lisinopril. By whole body autoradiography, radioactivity was found in the placenta following administration of labeled drug to rats, but none was found in the fetuses.

Pharmacodynamics

Administration of lisinopril to patients with hypertension results in a reduction of 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.)

In most patients studied, onset of antihypertensive activity was seen at one hour after oral administration of an individual dose of lisinopril, with peak reduction of blood pressure achieved by six hours.

In some patients achievement of optimal blood pressure reduction may require two to four week of therapy.

At recommended single daily doses, antihypertensive effects have been maintained for at least 24 hours after dosing, although the effect at 24 hours was substantially smaller than the effect six hours after dosing.

The antihypertensive effects of lisinopril have continued during long-term therapy. Abrupt withdrawal of lisinopril has not been associated with a rapid increase in blood pressure; nor with a significant overshoot of pretreatment blood pressure.

In hemodynamic studies 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 lisinopril, 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 lisinopril has been shown to be well tolerated and effective in controlling blood pressure (see PRECAUTIONS).

Hydrochlorothiazide

The mechanism of the antihypertensive effect of thiazides is unknown. Thiazides do not usually affect normal blood pressure.

Hydrochlorothiazide is a diuretic and antihypertensive. It affects the distal renal tubular mechanism of electrolyte reabsorption. Hydrochlorothiazide increases excretion of sodium and chloride in approximately equivalent amounts. Natriuresis may be accompanied by some loss of potassium and bicarbonate.

After oral use diuresis begins within two hours, peaks in about four hours and lasts about 6 to 12 hours.

Hydrochlorothiazide is not metabolized but is eliminated rapidly by the kidney. When plasma levels have been followed for at least 24 hours, the plasma half-life has been observed to vary between 5.6 and 14.8 hours. At least 61 percent of the oral dose is eliminated unchanged within 24 hours. Hydrochlorothiazide crosses the placental but not the blood-brain barrier.

INDICATIONS AND USAGE

Lisinopril and hydrochlorothiazide is indicated for the treatment of hypertension. These fixed-dose combinations are not indicated for initial therapy (see DOSAGE AND ADMINISTRATION).

In using lisinopril and hydrochlorothiazide, consideration should be given to the fact that an angiotensin converting enzyme inhibitor, captopril, has caused agranulocytosis, particularly in patients with renal impairment or collagen vascular disease, and that available data are insufficient to show that lisinopril does not have a similar risk. (See WARNINGS.)

In considering use of lisinopril and hydrochlorothiazide it should be noted that black patients receiving ACE inhibitors have been reported to have a higher incidence of angioedema compared to non-blacks. (See WARNINGS, Angioedema.)

CONTRAINDICATIONS

Lisinopril and hydrochlorothiazide is contraindicated in patients who are hypersensitive to any component of this product and in patients with a history of angioedema related to previous treatment with an angiotensin converting enzyme inhibitor and in patients with hereditary or idiopathic angioedema. Because of the hydrochlorothiazide component, this product is contraindicated in patients with anuria or hypersensitivity to other sulfonamide-derived drugs.

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