Captopril and Hydrochlorothiazide

Captopril and hydrochlorothiazide tablets are indicated for the treatment of hypertension. The blood pressure lowering effects of captopril and thiazides are approximately additive. This fixed combination drug may be used as initial therapy or substituted for previously titrated doses of the individual components. When captopril and hydrochlorothiazide are given together it may not be necessary to administer captopril in divided doses to attain blood pressure control at trough (before the next dose). Also, with such a combination, a daily dose of 15 mg of hydrochlorothiazide may be adequate. Treatment may, therefore, be initiated with captopril and hydrochlorothiazide tablets 25 mg/15 mg once daily.

The mechanism of action of captopril has not yet been fully elucidated. Its beneficial effects in hypertension and heart failure appear to result primarily from suppression of the renin-angiotensin-aldosterone system. However, there is no consistent correlation between renin levels and response to the drug. Renin, an enzyme synthesized by the kidneys, is released into the circulation where it acts on a plasma globulin substrate to produce angiotensin I, a relatively inactive decapeptide. Angiotensin I is then converted by angiotensin converting enzyme (ACE) to angiotensin II, a potent endogenous vasoconstrictor substance. Angiotensin II also stimulates aldosterone secretion from the adrenal cortex, thereby contributing to sodium and fluid retention. Captopril prevents the conversion of angiotensin I to angiotensin II by inhibition of ACE, a peptidyldipeptide carboxy hydrolase.

DOSAGE MUST BE INDIVIDUALIZED ACCORDING TO PATIENT'S RESPONSE. Captopril and hydrochlorothiazide tablets may be substituted for the previously titrated individual components. Alternatively, therapy may be instituted with a single tablet of captopril and hydrochlorothiazide 25 mg/15 mg taken once daily. For patients insufficiently responsive to the initial dose, additional captopril or hydrochlorothiazide may be added as individual components or by using captopril and hydrochlorothiazide tablets 50 mg/15 mg, 25 mg/25 mg or 50 mg/25 mg, or divided doses may be used. Because the full effect of a given dose may not be attained for 6 to 8 weeks, dosage adjustments should generally be made at 6 week intervals, unless the clinical situation demands more rapid adjustment.

Captopril: This product is contraindicated in patients who are hypersensitive to captopril or any other angiotensin-converting enzyme inhibitor (e.g., a patient who has experienced angioedema during therapy with any other ACE inhibitor). Hydrochlorothiazide: Hydrochlorothiazide is contraindicated in anuria. It is also contraindicated in patients who have previously demonstrated hypersensitivity to hydrochlorothiazide or other sulfonamide-derived drugs.

BOXED WARNING 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, captopril and hydrochlorothiazide should be discontinued as soon as possible. See WARNINGS: Captopril: Fetal/Neonatal Morbidity and Mortality. Captopril: Anaphylactoid and Possible Related Reactions: Presumably because angiotensin-converting enzyme inhibitors affect the metabolism of eicosanoids and polypeptides, including endogenous bradykinin, patients receiving ACE inhibitors (including captopril) may be subject to a variety of adverse reactions, some of them serious. Head and Neck Angioedema: Angioedema involving the extremities, face, lips, mucous membranes, tongue, glottis or larynx has been seen in patients treated with ACE inhibitors, including captopril.

Captopril: Reported incidences are based on clinical trials involving approximately 7000 patients. Renal: About one of 100 patients developed proteinuria. Each of the following has been reported in approximately 1 to 2 of 1000 patients and are of uncertain relationship to drug use: renal insufficiency, renal failure, nephrotic syndrome, polyuria, oliguria, and urinary frequency. Hematologic: Neutropenia/agranulocytosis has occurred. Cases of anemia, thrombocytopenia, and pancytopenia have been reported. Dermatologic: Rash, often with pruritus, and sometimes with fever, arthralgia, and eosinophilia, occurred in about 4 to 7 (depending on renal status and dose) of 100 patients, usually during the first four weeks of therapy. It is usually maculopapular, and rarely urticarial.

Captopril: Hypotension—Patients On Diuretic Therapy: Patients on diuretics and especially those in whom diuretic therapy was recently instituted, as well as those on severe dietary salt restrictions or dialysis, may occasionally experience a precipitous reduction of blood pressure usually within the first hour after receiving the initial dose of captopril. The possibility of hypotensive effects with captopril can be minimized by either discontinuing the diuretic or increasing the salt intake approximately one week prior to initiation of treatment with captopril or initiating therapy with small doses (6.25 or 12.5 mg). Alternatively, provide medical supervision for at least one hour after the initial dose. If hypotension occurs, the patient should be placed in a supine position and, if necessary, receive an intravenous infusion of normal saline.

Store at 20° to 25°C (68° to 77°F). Protect from moisture.