Wyeth-Ayerst has filed petitions opposing the creation of a bioequivalent version by Duramed Pharmaceuticals. They have argued that the generic version, using synthetic steroids, "lacked an important substance that is in Premarin".
Following these results, Wyeth experienced a significant decline in its sales of Premarin, Prempro (conjugated equine estrogens) and related hormones, from over $2 billion in 2002 to just over $1 billion in 2006. Research starting in 1975 showed substantially increased risk of endometrial cancer. Since 1976 the drug has carried a label warning about the risk. As part of the Women's Health Initiative sponsored by the National Institutes of Health, a large-scale clinical trial for Hormone Replacement Therapy showed that long-term use of progestin and estrogen may increase the risk of strokes, heart attacks, blood clots, and breast cancer.
Animal welfare groups claim that animal husbandry and urine collection methods used in Premarin's production cause undue stress and suffering to the mares involved. Allegations of abuse range from concern over stall size, access to water, exercise, cruel treatment, collection system, continuous breeding cycles, and premature death. And last but not least, the immediate killing of the foal and her immediate insemination.
Some of Premarin’s lesser known uses are the treatment of symptoms associated with metastatic breast cancer in men and women and prostate cancer in men. It can also be used for individuals that do not produce enough estrogen due to hypogonadism, castration, and ovarian failure, or who have certain intersex conditions such as Androgen insensitivity syndrome.
The most common side effects associated with Premarin use are vaginal yeast infections, vaginal spotting or bleeding, painful menses, and cramping of the legs. For women already taking the drug it can be used to treat osteoporosis, although it is not recommended solely for this use. It can also be used in conjunction with a progestin pill in women who have not had a hysterectomy. Premarin pills are used most commonly in post menopausal women who have had a hysterectomy to treat hot flashes, and burning, itching, and dryness of the vagina and surrounding areas. Premarin is a form of hormone replacement therapy.
Premarin cream is only used for vaginal burning, dryness and itching. While there are some contradictory data, estrogen alone does not appear to increase the risk of coronary heart disease or breast cancer, like estrogen with progestin does. While estrogen alone appears to decrease the risk of hip fracture for women who have had a hysterectomy, it is still suggested that Premarin be used for the shortest period of time and at the smallest possible dose that is effective in alleviating symptoms because it can increase the risk of endometrial cancer, stroke, blood clots, and possibly dementia.
Note: Though not listed here, many anabolic steroids can also be estrogenic as they can be aromatized into estrogen-like metabolites that possess estrogenic activity.
However, Wyeth and Pharmacia & Upjohn have prevailed in the vast majority of hormone therapy cases previously set for trial through a combination of rulings by judges, verdicts by juries, and dismissals by plaintiffs themselves. Wyeth has won the last four of five cases, most recently in Virginia, finding that Wyeth was not responsible for Plaintiff Georgia Torkie-Tork's breast cancer. Wyeth also has won five summary judgments on Prempro cases and had 15 cases that were set for trial voluntarily dismissed by plaintiffs. This drug has been the subject of litigation; more than 13,000 people have sued Wyeth between 2002 and 2009. Wyeth has been quoted as saying "many risk factors associated with breast cancer have been identified, but science cannot establish what role any particular risk factor or combination play in any individual woman's breast cancer." Wyeth's counsel in the case also noted that in the WHI trial, 99.62 percent of women took the drug and "did not get breast cancer.". In 2006, Mary Daniel, in a trial in Philadelphia, PA, was awarded $1.5 million in compensatory damages as well as undisclosed punitive damages. Of the company’s losses, two of the jury verdicts were reversed post-trial and others are being challenged on appeal. The company has won dismissals in another 3,000 cases.
Estrone sulfate is converted to estradiol, an active estrogen normally found in women. Thus, estrone sulfate is actually the major active constituent in Premarin. It is not clear if estrogens such as equilin that are foreign to the human body have effects in women that are significantly different from the estrogens like estradiol that are normally made in the human body. Estrone sulfate is easily absorbed into the blood after Premarin pills are taken by women. The major forms of estrogen in Premarin are estrone (>50%), equilin (15-25%) and equilenin. Estrone sulfate Equilin sulfate Equilenin sulfate. The estrogens in Premarin are often called "conjugated equine estrogens" (CEE) because the estrogen molecules are generally present with hydrophilic side-groups attached such as sulfate.
Note: Xenoestrogens (e.g., phytoestrogens and mycoestrogens ) are not included here. For a full list of xenoestrogens, see here.
Premarin is the commercial name for a medication consisting primarily of conjugated estrogens. Isolated from mares ' urine ( pre gnant mar es' ur in e), it is manufactured by Wyeth Pharmaceuticals (part of Pfizer since January 2009) and has been marketed since 1942. It is available in oral (0.3/0.45/0.625/0.9/1.25 mg), IV, and topical ( vaginal ) form.
Note: 5α-reductase and 21-hydroxylase inhibitors may also affect estrogen levels as they prevent metabolism of estrogen steroid precursors.