The National Women's Health Network is putting pressure on US regulators to pull oestrogen/testosterone combos made by Solvay and Breckenridge Pharmaceutical off the shelves, because their safety and efficacy has not been proven.

Solvay’s Estratest has been on the US market since 1964 and Breckenridge’s Syntest since 1997 for the treatment of menopausal symptoms, but neither “has been approved by the FDA [Food and Drug Administration] for the labelled indications for which they marketed,” the petition notes.

“In 2003, the FDA concluded that there is no substantial evidence of efficacy of oestrogen/testosterone for the treatment of vasomotor symptoms that don’t respond to treatment with exogenous oestrogen alone,” it says, and further points out that “according to reviews by the FDA’s own medical staff and the findings of its scientific advisors, there are significant known risks associated with oestrogen/testosterone products.”

The group says that continued marketing of Estratest and Sytnest puts the health of women exposed to these products “at significant risk,” and has therefore called on regulators to withdraw their use until a safety and efficacy profile can be established.

A spokesperson for Solvay was not available for comment.