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Review of the Food and Drug Administration's Handling of Issues Related to Conjugated Estrogens

Issued on  | Posted on  | Report number: A-15-96-50002

Report Materials


This report provides the results of our review of the Food and Drug Administration's (FDA) handling of issues related to conjugated estrogens (Premarin), a commonly prescribed product for menopausal symptoms and the prevention and management of osteoporosis. This review was performed at the request of the Chairman, Subcommittee on Oversight and Investigations, House Committee on Commerce.

The FDA is the Federal agency responsible for approving applications to market new drugs, new indications for already marketed drugs, and generic versions of brand name drugs. Conjugated estrogens products represent a class of marketed drugs used primarily for the treatment of menopausal symptoms in women and for the prevention and management of osteoporosis, a crippling disease that causes thinning of the bone. Wyeth-Ayerst is a drug manufacturer that markets: (1) Premarin, approved in 1942, which is made from the urine of pregnant mares and is the Nation's only conjugated estrogens product; and (2) Prempro, approved in 1994, which combines Premarin and another hormone called progestin. At this time, there are no approved applications to market generic versions of these brand name drugs.

Once a drug is approved, drug manufacturers are required to obtain FDA's approval before adding or deleting an ingredient, or otherwise changing the composition of a drug product, other than deletion of an ingredient intended only to affect the color of the drug product. Current regulations require that when there is a change in the manufacturing process, including a change in product formulation or dosage strength, beyond the variations provided for in the approved application, drug manufacturers are required to show that any reformulations are bioequivalent to the approved product.

The FDA uses a process called the citizen petition to allow anyone--individuals or companies--to request the agency to make changes to its regulations. In November 1994, Wyeth-Ayerst submitted a citizen petition requesting FDA to: (1) recognize an ingredient of Premarin--delta 8,9 (dehydroestrone sulfate (DHES))--as an essential (but not an active) ingredient in Premarin; and (2) not approve any generic version of Premarin that does not contain DHES. The firm amended its petition in December 1996 to request FDA to recognize DHES as an active ingredient. To date, FDA has not made a decision as to whether to approve Wyeth-Ayerst's citizen petition request. However, on May 5, 1997, FDA's Director, Center for Drug Evaluation and Research (CDER), announced that, because the active ingredients of Premarin have not been adequately defined, the agency could not at this time approve generic applications for synthetic versions of conjugated estrogens. The FDA had been reviewing two such applications since 1994 and 1995, respectively.

The House Committee on Commerce, Subcommittee on Oversight and Investigations, has raised concerns that Wyeth-Ayerst may have made misrepresentations in its submissions to FDA regarding Premarin, and that FDA may have failed to adequately review such submissions. The Subcommittee requested the Office of Inspector General (OIG) in July 1996 to answer specific questions regarding: Premarin, another Wyeth-Ayerst product called Prempro, the citizen petition related to Premarin, and generic versions of Premarin.

Our objective was to answer the Subcommittee's questions in the following three areas:

  1. Premarin: The questions focused on possible unapproved reformulations; whether the reformulations were bioequivalent; and the basis on which FDA allowed the continued marketing of Premarin.

  2. Prempro: The question focused on the basis on which Wyeth-Ayerst won approval for Prempro's use in the prevention and management of osteoporosis.

  3. Wyeth-Ayerst's citizen petition regarding Premarin and generic versions of Premarin: The questions focused on FDA's examination of data and claims made in Wyeth-Ayerst's citizen petition and the agency's handling of brand name and generic versions of Premarin.

Premarin: According to FDA, there have been no unapproved formulations of Premarin. Regarding the issue of bioequivalency among the formulations, however, we found that FDA does not have evidence demonstrating that the currently marketed formulation of Premarin is bioequivalent to the version tested for osteoporosis in the late 1970's. This is because no in vivo (i.e., in the living body) bioequivalence requirement was in effect for conjugated estrogens at that time. Concerned about lack of bioequivalency data and the continued safety and effectiveness of Premarin, FDA in 1993 directed Wyeth-Ayerst to conduct a new dose-ranging study of the drug. As of January 1997, 818 women, or about 30 percent of the total planned enrollment of 2,688, have entered into the multi-year study.

Prempro: The Premarin tablet formulation used in the combination drug Prempro (Premarin/medroxyprogesterone acetate) slightly differed from the marketed Premarin, but Wyeth-Ayerst submitted in vivo bioequivalence data to demonstrate that the new and currently marketed formulations were bioequivalent.

Citizen Petition and Generic Versions of Premarin: The FDA is in the process of reviewing the claims and data associated with Wyeth-Ayerst's citizen petition, which was submitted to the agency over 2 years ago. The FDA has thus far found deficiencies in the design of studies submitted to support Wyeth-Ayerst's claims, but no misrepresentations in data in the firm's studies have been identified. Regarding the Subcommittee's concern that FDA may have held generic drug firms to a higher standard than the brand-name maker of Premarin, Wyeth-Ayerst, we noted that the agency was also concerned about possible differing standards in terms of bioequivalency requirements for the generic and brand name versions. However, upon further investigation, FDA determined there were no unapproved reformulations of the brand name Premarin that would have required Wyeth-Ayerst to submit additional bioequivalency data.

Beyond the Subcommittee's specific questions, we identified other concerns regarding the citizen petition process--namely that the process has been extended for an excessive period of time in the Wyeth-Ayerst case; and FDA does not have policies and procedures governing such an important process, one which can impact the marketability of generic versions of Premarin.