Premarin Intravenous (conjugated estrogens, USP) for injection contains a mixture of conjugated estrogens obtained exclusively from natural sources, occurring as the sodium salts of water-soluble estrogen sulfates blended to represent the average composition of materials derived from pregnant mares' urine. It is a mixture of sodium estrone sulfate and sodium equilin sulfate. It contains as concomitant components, as sodium sulfate conjugates, 17α-dihydroequilin, 17α-estradiol, and 17β-dihydroequilin.
Each single-dose vial contains 25 mg/vial of conjugated estrogens, USP, in a sterile lyophilized cake which also contains lactose 200 mg, sodium citrate 12.2 mg, and simethicone 0.2 mg. The pH is adjusted with sodium hydroxide or hydrochloric acid. The reconstituted solution is suitable for intravenous or intramuscular injection.