Premarin^® (conjugated estrogens) is a medication licensed for several uses, such as treating menopausal symptoms, preventing osteoporosis, and reducing the symptoms of certain cancers. This prescription drug is a mixture of natural equine (horse) estrogens. Premarin comes in tablet form and is typically taken once a day. The dose of Premarin your healthcare provider recommends will be based on several factors, such as the medical condition being treated, whether you have had a hysterectomy, and other medical conditions you have.