PREMARIN is a prescription medication manufactured by Pfizer Inc., containing a mixture of conjugated estrogens derived from the urine of pregnant mares. These estrogens are primarily sodium estrone sulfate and sodium equilin sulfate, along with other estrogenic compounds. PREMARIN is available in tablet form in various strengths, including 0.3 mg, 0.45 mg, 0.625 mg, 0.9 mg, and 1.25 mg .