Indomethacin for Injection - Scientific Information
|Manufacture:||Fresenius Kabi USA, LLC|
|Condition:||Ankylosing Spondylitis, Cluster Headaches, Gout, Acute, Patent Ductus Arteriosus|
|Class:||Nonsteroidal anti-inflammatory agents|
|Form:||Intravenous (IV), Powder|
|Ingredients:||Indomethacin, Monobasic Sodium Phosphate, Dibasic Sodium Phosphate, not more than 0.24 mg of Sodium Hydroxide|
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.
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:
C19H16ClNO4 M.W. 357.8
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.
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.
The disposition of indomethacin following intravenous administration (0.2 mg/kg) in pre-term neonates with patent ductus arteriosus has not been extensively evaluated. Even though the plasma half-life of indomethacin was variable among premature infants, it was shown to vary inversely with postnatal age and weight. In one study, of 28 neonates who could be evaluated, the plasma half-life in those less than 7 days old averaged 20 hours (range: 3 to 60 hours, n=18). In neonates older than 7 days, the mean plasma half-life of indomethacin was 12 hours (range: 4 to 38 hours, n=10). Grouping the neonates by weight, mean plasma half-life in those weighing less than 1,000 g was 21 hours (range: 9 to 60 hours, n=10); in those neonates weighing more than 1,000 g, the mean plasma half-life was 15 hours (range: 3 to 52 hours, n=18).
Following intravenous administration in adults, indomethacin is eliminated via renal excretion, metabolism, and biliary excretion. Indomethacin undergoes appreciable enterohepatic circulation. The mean plasma half-life of indomethacin is 4.5 hours. In the absence of enterohepatic circulation, it is 90 minutes. Indomethacin has been found to cross the blood-brain barrier and the placenta.
In adults, about 99 percent of indomethacin is bound to protein in plasma over the expected range of therapeutic plasma concentrations. The percent bound in neonates has not been studied. In controlled trials in premature infants, however, no evidence of bilirubin displacement has been observed as evidenced by increased incidence of bilirubin encephalopathy (kernicterus).
In rats and mice, oral indomethacin 4 mg/kg/day given during the last three days of gestation caused a decrease in maternal weight gain and some maternal and fetal deaths. An increased incidence of neuronal necrosis in the diencephalon in the live-born fetuses was observed. At 2 mg/kg/day, no increase in neuronal necrosis was observed as compared to the control groups. Administration of 0.5 or 4 mg/kg/day during the first three days of life did not cause an increase in neuronal necrosis at either dose level.
Pregnant rats, given 2 mg/kg/day and 4 mg/kg/day during the last trimester of gestation, delivered offspring whose pulmonary blood vessels were both reduced in number and excessively muscularized. These findings are similar to those observed in the syndrome of persistent pulmonary hypertension of the neonate.