The Food and Drug Administration on Friday clarified a guidance document it had given drugmakers several years ago to ensure that an implant on the breast might deliver a single dose of a given drug.

The FDA said it would revise the guidance document to make sure that implanted devices are efficiently delivered. Currently it advises women to use one dose of a drug given every two weeks for no more than six months.

The guidance has remained consistent in the roughly 50 years since the first recommendations were issued a spokeswoman for the agency told Reuters.

In 2016 the FDA changed its guidance on implant sizes to incorporate the final version released by the European Medicines Agency.

The agency has been criticized over the continued use of chemical aids to improve outcomes for women with hormone-related cancers in the past an indication that medical practices have removed the safety and effectiveness limitations that made it possible for the devices to be used at lower doses.

The new guidance was released as part of a push to reduce the toxicity of early and mid-cycle hormonal implantable devices as it considered the impact such devices could have on women with cancer. It also would improve the FDAs provision for implant safety tests researchers said.

A final version released by the FDA was due to be voted on Monday but was postponed as the agency grapples with the guidance following a question about whether a paper leaked to the media suggested implant size restrictions were fair game.

FDA head Steven M. Patterson said last week his agency had removed the proposal from its website because the source asked for the draft guidance to be removed.

Department of Health and Human Services officials had told Reuters in October they expected to have more information in February or March on how women with small-cell estrogenic implants would perform how use of such devices might change in the presence of chemotherapy and other toxicological studies.

Others criticized the FDAs new guidance which focused largely on the need for state-of-the-art imaging to inform implant placement and in particular the dosimetric implications of implant use in women with breast cancer said Brienne Ikhs-Clements a New York University doctoral student who said she voted yes on Friday.

According to the American Cancer Society about 1. 9 million women with breast cancer are using implantable devices and the estimated 800000 deaths yearly attributable to such devices is high. FDA officials declined to comment on the new guidance referring to a 2016 document in the Journal of the American Medical Association that they did not back.

The FDA in 2016 put out a guidance document urging officials to ensure implant sizes for women with the most common indications for hormone-controlling devices 1. 5-7. 5 times larger than the current labeling that was used at the time.

Patients with tumors in which a hormone-yielding cancerogenetic pathway is inhibited were urged to use smaller implant sizes if the therapy had been approved by a regulatory authority in that country but not if the protocol was not well-established there.

Data released by the agency showed that about 3. 5 percent of implantable device use was high-risk meaning the devices were designed for very aggressive or metastatic breast cancers where hormone therapy would not be curative.

For women with types of patients that have not yet responded to hormone therapy low-risk implantable devices include self-administration of oxytocin given when the hormone is released to ease the discomfort and tiredness that comes with not having access to the hormone for years. It is not possible to keep the devices in place indefinitely.