Indomethacin (Page 2 of 3)

6.1 Clinical Trials Experience

In a double-blind, placebo-controlled trial of 405 premature infants weighing less than or equal to 1,750 g with evidence of large ductal shunting, in those neonates treated with indomethacin (n=206), there was a statistically significantly greater incidence of bleeding problems, including gross or microscopic bleeding into the gastrointestinal tract, oozing from the skin after needle stick, pulmonary hemorrhage, and disseminated intravascular coagulopathy. There was no statistically significant difference between treatment groups in intracranial hemorrhage.

The neonates treated with Indomethacin for Injection had a significantly higher incidence of transient oliguria and elevations of serum creatinine (greater than or equal to 1.8 mg/dL) than did the neonates treated with placebo.

The incidences of retrolental fibroplasia (grades III and IV) and pneumothorax in neonates treated with Indomethacin for Injection were no greater than in placebo controls and were statistically significantly lower than in surgically-treated neonates.

The following additional adverse reactions in neonates have been reported from the collaborative study, anecdotal case reports, from other studies using rectal, oral, or intravenous indomethacin for treatment of patent ductus arteriosus or in marketed use. The rates are calculated from a database that contains experience of 849 indomethacin-treated neonates reported in the medical literature, regardless of the route of administration. One year follow-up is available on 175 neonates and shows no long-term sequelae that could be attributed to indomethacin. In controlled clinical studies, only electrolyte imbalance and renal dysfunction (of the reactions listed below) occurred statistically significantly more frequently after Indomethacin for Injection than after placebo. Reactions marked with a single asterisk (*) occurred in 3 to 9 percent of indomethacin-treated neonates; those marked with a double asterisk (**) occurred in 3 to 9 percent of both indomethacin- and placebo-treated neonates. Unmarked reactions occurred in less than 3 percent of neonates.

Renal: renal failure, renal dysfunction in 41 percent of neonates, including one or more of the following: reduced urinary output; reduced urine sodium, chloride, or potassium, urine osmolality, free water clearance, or glomerular filtration rate; elevated serum creatinine or BUN; uremia.

Cardiovascular: intracranial bleeding**, pulmonary hypertension.

Gastrointestinal: gastrointestinal bleeding*, vomiting, abdominal distention, transient ileus, gastric perforation, localized perforation(s) of the small and/or large intestine, necrotizing enterocolitis.

Metabolic: hyponatremia*, elevated serum potassium*, reduction in blood sugar, including hypoglycemia, increased weight gain (fluid retention).

Coagulation: decreased platelet aggregation [see Warnings and Precautions (5.3)].

The following adverse reactions have also been reported in neonates treated with indomethacin, however, a causal relationship to therapy with Indomethacin for Injection has not been established:

Cardiovascular: bradycardia.

Respiratory: apnea, exacerbation of pre-existing pulmonary infection.

Metabolic: acidosis/alkalosis.

Hematologic: disseminated intravascular coagulation, thrombocytopenia.

Ophthalmic: retrolental fibroplasia.**

Dermatologic: drug reaction with eosinophilia and systemic symptoms (DRESS)

A variety of additional adverse experiences have been reported in adults treated with oral indomethacin for moderate to severe rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, acute painful shoulder and acute gouty arthritis (see package insert for oral indomethacin for additional information concerning adverse reactions and other cautionary statements). Their relevance to the pre-term infant receiving indomethacin for patent ductus arteriosus is unknown, however, the possibility exists that these experiences may be associated with the use of Indomethacin for Injection in pre-term infants.

7 DRUG INTERACTIONS

As renal function may be reduced by Indomethacin for Injection, consider reducing the dosage of those medications that rely on adequate renal function for their elimination.

7.1 Digoxin

Because the half-life of digoxin (given frequently to pre-term infants with patent ductus arteriosus and associated cardiac failure) may be prolonged when given concomitantly with indomethacin, observe neonates receiving concomitant digoxin closely; frequent ECGs and serum digoxin levels may be required to prevent or detect digoxin toxicity early.

7.2 Anticoagulants

Indomethacin usually does not influence the hypoprothrombinemia produced by anticoagulants. When indomethacin is added to anticoagulants, monitor prothrombin time closely. In post-marketing experience, bleeding has been reported in patients on concomitant treatment with anticoagulants and Indomethacin for Injection.

7.3 Furosemide

Therapy with indomethacin may blunt the natriuretic effect of furosemide. This response has been attributed to inhibition of prostaglandin synthesis by non-steroidal anti-inflammatory drugs. In a study of 19 premature infants with patent ductus arteriosus treated with either Indomethacin for Injection alone or a combination of Indomethacin for Injection and furosemide, results showed that neonates receiving both Indomethacin for Injection and furosemide had significantly higher urinary output, higher levels of sodium and chloride excretion, and higher glomerular filtration rates than did those receiving Indomethacin for Injection alone. In this study, therapy with furosemide helped to maintain renal function in the premature infant when Indomethacin for Injection was added.

7.4 Aminoglycosides

In one study of premature infants treated with Indomethacin for Injection and also receiving either gentamicin or amikacin, both peak and trough levels of these aminoglycosides were significantly elevated.

7.5 Drugs that Act on the Renin-Angiotensin System

In some patients with compromised renal function, the co-administration of an NSAID and an ACE inhibitor or angiotensin II antagonist may result in further deterioration of renal function, including possible acute renal failure, which is usually reversible.

11 DESCRIPTION

Sterile Indomethacin for Injection for intravenous administration is lyophilized indomethacin for injection. Each vial of indomethacin for injection contains 1 mg indomethacin; 0.29 mg monobasic sodium phosphate, 0.41 mg dibasic sodium phosphate and not more than 0.24 mg of sodium hydroxide (used for converting indomethacin base to the sodium salt) as a white to yellow lyophilized powder or plug. Variations in the size of the lyophilized plug and the intensity of color have no relationship to the quality or amount of indomethacin present in the vial. If necessary, hydrochloric acid (q.s.) and sodium hydroxide (q.s.) are added as pH adjusters. The reconstituted solution, pH 6.0 to 7.5, is clear, slightly yellow and essentially free from visible particles. The pH of the product does not meet the USP monograph [FD&C Act Chapter V, SEC. 501. [21USC §351](b)].

Indomethacin is designated chemically as 1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid. The structural formula is:

Structural Formula

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Although the exact mechanism of action through which indomethacin causes closure of a patent ductus arteriosus is not known, it is believed to be through inhibition of prostaglandin synthesis.

12.2 Pharmacodynamics

Indomethacin has been shown to be a potent inhibitor of prostaglandin synthesis, both in vitro and in vivo. In human newborns with certain congenital heart malformations, PGE 1 dilates the ductus arteriosus. In fetal and newborn lambs, E type prostaglandins have also been shown to maintain the patency of the ductus, and as in human newborns, indomethacin causes its constriction.

Studies in healthy young animals and in premature infants with patent ductus arteriosus indicated that, after the first dose of intravenous indomethacin, there was a transient reduction in cerebral blood flow velocity and cerebral blood flow. Similar decreases in mesenteric blood flow and velocity have been observed. The clinical significance of these effects has not been established.

In double-blind, placebo-controlled studies of Indomethacin for Injection in 460 small pre-term infants, weighing 1,750 g or less, the neonates treated with placebo had a ductus closure rate after 48 hours of 25 to 30 percent, whereas those treated with Indomethacin for Injection had a 75 to 80 percent closure rate. In one of these studies, a multicenter study, involving 405 pre-term infants, later reopening of the ductus arteriosus occurred in 26 percent of neonates treated with Indomethacin for Injection however, 70 percent of these closed subsequently without the need for surgery or additional indomethacin.

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