INDAPAMIDE TABLETS USP

Rx only

Indapamide is an oral antihypertensive/diuretic. Its molecule contains both a polar sulfamoyl chlorobenzamide moiety and a lipid-soluble methylindoline moiety. It differs chemically from the thiazides in that it does not possess the thiazide ring system and contains only one sulfonamide group. The chemical name of indapamide is 4-Chloro-N-(2-methyl-1-indolinyl)-3-sulfamoylbenzamide, and its molecular weight is 365.84. The compound is a weak acid, pK_a = 8.8, and is soluble in aqueous solutions of strong bases. It is a white to yellow-white crystalline (tetragonal) powder.

Each tablet, for oral administration, contains indapamide 1.25 mg or 2.5 mg. In addition, each tablet contains the following inactive ingredients: FD&C Yellow No. 6 (1.25 mg), hypromellose, lactose monohydrate, magnesium stearate, maize starch, microcrystalline cellulose, polyethylene glycol, povidone and titanium dioxide.

Indapamide is the first of a new class of antihypertensive/diuretics, the indolines. It has been reported that the oral administration of 2.5 mg (two 1.25 mg tablets) of indapamide to male subjects produced peak concentrations of approximately 115 ng/mL of the drug in blood within two hours. It has been reported that the oral administration of 5 mg (two 2.5 mg tablets) of indapamide to healthy male subjects produced peak concentrations of approximately 260 ng/mL of the drug in the blood within two hours. A minimum of 70% of a single oral dose is eliminated by the kidneys and an additional 23% by the gastrointestinal tract, probably including the biliary route. The half-life of indapamide in whole blood is approximately 14 hours.

Indapamide is preferentially and reversibly taken up by the erythrocytes in the peripheral blood. The whole blood/plasma ratio is approximately 6:1 at the time of peak concentration and decreases to 3.5:1 at eight hours. From 71 to 79% of the indapamide in plasma is reversibly bound to plasma proteins.

Indapamide is an extensively metabolized drug with only about 7% of the total dose administered, recovered in the urine as unchanged drug during the first 48 hours after administration. The urinary elimination of ¹⁴C-labeled indapamide and metabolites is biphasic with a terminal half-life of excretion of total radioactivity of 26 hours.

In a parallel design double-blind, placebo controlled trial in hypertension, daily doses of indapamide between 1.25 mg and 10 mg produced dose-related antihypertensive effects. Doses of 5 mg and 10 mg were not distinguishable from each other although each was differentiated from placebo and 1.25 mg indapamide. At daily doses of 1.25 mg, 5 mg and 10 mg, a mean decrease of serum potassium of 0.28, 0.61 and 0.76 mEq/L, respectively, was observed and uric acid increased by about 0.69 mg/100 mL.

In other parallel design, dose-ranging clinical trials in hypertension and edema, daily doses of indapamide between 0.5 and 5 mg produced dose-related effects. Generally, doses of 2.5 and 5 mg were not distinguishable from each other although each was differentiated from placebo and from 0.5 or 1 mg indapamide. At daily doses of 2.5 and 5 mg a mean decrease of serum potassium of 0.5 and 0.6 mEq/Liter, respectively, was observed and uric acid increased by about 1 mg/100 mL.

At these doses, the effects of indapamide on blood pressure and edema are approximately equal to those obtained with conventional doses of other antihypertensive/diuretics.

In hypertensive patients daily doses of 1.25, 2.5 and 5 mg of indapamide have no appreciable cardiac inotropic or chronotropic effect. The drug decreases peripheral resistance, with little or no effect on cardiac output, rate or rhythm. Chronic administration of indapamide to hypertensive patients has little or no effect on glomerular filtration rate or renal plasma flow.

Indapamide had an antihypertensive effect in patients with varying degrees of renal impairment, although in general, diuretic effects declined as renal function decreased.

In a small number of controlled studies, indapamide taken with other antihypertensive drugs such as hydralazine, propranolol, guanethidine, and methyldopa, appeared to have the additive effect typical of thiazide-type diuretics.

Indapamide is indicated for the treatment of hypertension, alone or in combination with other antihypertensive drugs.

Indapamide is also indicated for the treatment of salt and fluid retention associated with congestive heart failure.

The routine use of diuretics in an otherwise healthy woman is inappropriate and exposes mother and fetus to unnecessary hazard (see PRECAUTIONS). Diuretics do not prevent development of toxemia of pregnancy, and there is no satisfactory evidence that they are useful in the treatment of developed toxemia.

Edema during pregnancy may arise from pathological causes or from the physiologic and mechanical consequences of pregnancy. Indapamide is indicated in pregnancy when edema is due to pathologic causes, just as it is in the absence of pregnancy (however, see PRECAUTIONS). Dependent edema in pregnancy, resulting from restriction of venous return by the expanded uterus, is properly treated through elevation of the lower extremities and use of support hose; use of diuretics to lower intravascular volume in this case is illogical and unnecessary. There is hypervolemia during normal pregnancy which is not harmful to either the fetus or the mother (in the absence of cardiovascular disease), but which is associated with edema, including generalized edema in the majority of pregnant women. If this edema produces discomfort, increased recumbency will often provide relief. In rare instances, this edema may cause extreme discomfort which is not relieved by rest. In these cases, a short course of diuretics may provide relief and may be appropriate.

Anuria.

Known hypersensitivity to indapamide or to other sulfonamide-derived drugs.

Severe cases of hyponatremia, accompanied by hypokalemia, have been reported with recommended doses of indapamide. This occurred primarily in elderly females. This appears to be dose-related. Also a large case-controlled pharmacoepidemiology study indicates that there is an increased risk of hyponatremia with indapamide 2.5 mg and 5 mg doses. Hyponatremia considered possibly clinically significant (less than 125 mEq/L) has not been observed in clinical trials with the 1.25 mg dosage (see PRECAUTIONS). Thus patients should be started at the 1.25 mg dose and maintained at the lowest possible dose. (See DOSAGE AND ADMINISTRATION).

Hypokalemia occurs commonly with diuretics (see ADVERSE REACTIONS), and electrolyte monitoring is essential, particularly in patients who would be at increased risk from hypokalemia, such as those with cardiac arrhythmias or who are receiving concomitant cardiac glycosides.

In general, diuretics should not be given concomitantly with lithium because they reduce its renal clearance and add a high risk of lithium toxicity. Read prescribing information for lithium preparations before use of such concomitant therapy.

Both mouse and rat lifetime carcinogenicity studies were conducted. There was no significant difference in the incidence of tumors between the indapamide-treated animals and the control groups.

It is not known whether this drug is excreted in human milk. Because most drugs are excreted in human milk, if use of this drug is deemed essential, the patient should stop nursing.

Safety and effectiveness of indapamide in pediatric patients have not been established.

Most adverse effects have been mild and transient.

The Clinical Adverse Reactions uled in Table 1 represent data from Phase II/III placebo-controlled studies (306 patients given indapamide 1.25 mg). The clinical adverse reactions uled in Table 2 represent data from Phase II placebo-controlled studies and long-term controlled clinical trials (426 patients given indapamide 2.5 mg or 5 mg). The reactions are arranged into two groups: 1) a cumulative incidence equal to or greater than 5%; 2) a cumulative incidence less than 5%. Reactions are counted regardless of relation to drug.

All other clinical adverse reactions occurred at an incidence of <1%.

Approximately 4% of patients given indapamide 1.25 mg compared to 5% of the patients given placebo discontinued treatment in the trials of up to eight weeks because of adverse reactions.

In controlled clinical trials of six to eight weeks in duration, 20% of patients receiving indapamide 1.25 mg, 61% of patients receiving indapamide 5 mg, and 80% of patients receiving indapamide 10 mg had at least one potassium value below 3.4 mEq/L. In the indapamide 1.25 mg group, about 40% of those patients who reported hypokalemia as a laboratory adverse event returned to normal serum potassium values without intervention. Hypokalemia with concomitant clinical signs or symptoms occurred in 2% of patients receiving indapamide 1.25 mg.

Because most of these data are from long-term studies (up to 40 weeks of treatment), it is probable that many of the adverse experiences reported are due to causes other than the drug. Approximately 10% of patients given indapamide discontinued treatment in long-term trials because of reactions either related or unrelated to the drug.

Hypokalemia with concomitant clinical signs or symptoms occurred in 3% of patients receiving indapamide 2.5 mg q.d. and 7% of patients receiving indapamide 5 mg q.d. In long-term controlled clinical trials comparing the hypokalemic effects of daily doses of indapamide and hydrochlorothiazide, however, 47% of patients receiving indapamide 2.5 mg, 72% of patients receiving indapamide 5 mg, and 44% of patients receiving hydrochlorothiazide 50 mg had at least one potassium value (out of a total of 11 taken during the study) below 3.5 mEq/L. In the indapamide 2.5 mg group, over 50% of those patients returned to normal serum potassium values without intervention.

In clinical trials of six to eight weeks, the mean changes in selected values were as shown in the tables below.

No patients receiving indapamide 1.25 mg experienced hyponatremia considered possibly clinically significant (<125 mEq/L).

Indapamide had no adverse effects on lipids.

The following reactions have been reported with clinical usage of indapamide: jaundice (intrahepatic cholestatic jaundice), hepatitis, pancreatitis, and abnormal liver function tests. These reactions were reversible with discontinuance of the drug.

Also reported are erythema multiforme, Stevens-Johnson Syndrome, bullous eruptions, purpura, photosensitivity, fever, pneumonitis, anaphylactic reactions, agranulocytosis, leukopenia, thrombocytopenia and aplastic anemia. Other adverse reactions reported with antihypertensive/ diuretics are necrotizing angiitis, respiratory distress, sialadenitis, xanthopsia.

Symptoms of overdosage include nausea, vomiting, weakness, gastrointestinal disorders and disturbances of electrolyte balance. In severe instances, hypotension and depressed respiration may be observed. If this occurs, support of respiration and cardiac circulation should be instituted. There is no specific antidote. An evacuation of the stomach is recommended by emesis and gastric lavage after which the electrolyte and fluid balance should be evaluated carefully.

The adult starting indapamide dose for hypertension is 1.25 mg as a single daily dose taken in the morning. If the response to 1.25 mg is not satisfactory after four weeks, the daily dose may be increased to 2.5 mg taken once daily. If the response to 2.5 mg is not satisfactory after four weeks, the daily dose may be increased to 5 mg taken once daily, but adding another antihypertensive should be considered.

The adult starting indapamide dose for edema of congestive heart failure is 2.5 mg as a single daily dose taken in the morning. If the response to 2.5 mg is not satisfactory after one week, the daily dose may be increased to 5 mg taken once daily.

If the antihypertensive response to indapamide is insufficient, indapamide may be combined with other antihypertensive drugs, with careful monitoring of blood pressure. It is recommended that the usual dose of other agents be reduced by 50% during initial combination therapy. As the blood pressure response becomes evident, further dosage adjustments may be necessary.

In general, doses of 5 mg and larger have not appeared to provide additional effects on blood pressure or heart failure, but are associated with a greater degree of hypokalemia. There is minimal clinical trial experience in patients with doses greater than 5 mg once a day.

Indapamide Tablets are available as follows:

1.25 mg (Orange film coated, normal convex, round tablet, debossed IE 1.25 on one side and G on the reverse)

Bottles of 100 NDC 57315-027-01

Bottles of 1000 NDC 57315-027-02

2.5 mg (White film coated, normal convex, round tablet, debossed IE 2.5 on one side and G on the reverse)

Bottles of 100 NDC 57315-028-01

Bottles of 1000 NDC 57315-028-02

Keep tightly closed. Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].

Avoid excessive heat. Dispense in tight containers as defined in USP.

464/5 Revised September 2005

MANUFACTURED BY:

ALPHAPHARM PTY LTD

15 Garnet St

Carole Park QLD 4300

Australia