A U. S. court on Monday was asked by Sanofi-Aventis (SASY. PA) to block the approval of a generic version of its widely used blood clot treatment Lovenox. They said that last week the medicine got approval improperly by federal regulators.

The first generic version of Lovenox for the Sandoz generic drug unit of Switzerland's Novartis AG (NOVN. VX) was cleared by the U. S. Food and Drug Administration on Friday.

A temporary restraining order and a preliminary injunction that would require the FDA to withdraw its approval was asked by Sanofi from the U. S. District Court for the District of Columbia. Sanofi argued that the decision was uninformed and unpredictable.

The French drugmaker argued that the FDA could not ensure that Sandoz's drug also contains the same active ingredient as Lovenox. It also argued that Sandoz was improperly allowed by federal regulators to rely on Sanofi's proprietary information.

Sanofi said in court papers, "If not remedied, FDA's decision will cause Sanofi-Aventis irreparable harm and may result in entry into the market of a generic product that is not clinically equivalent to Lovenox with respect to safety or efficacy."