WASHINGTON, Feb 7 (Reuters) - A federal judge on Tuesday upheld the Food and Drug Administration's approval of the generic version of the blood thinner Lovenox sold by Novartis AG's Sandoz and Momenta Pharmaceuticals.

The maker of Lovenox, Sanofi-Aventis, had sued the FDA in 2010, arguing that the agency had not followed its procedures and did not ensure that the generic, known as enoxaparin, had the same active ingredient as the name-brand version.

U.S. District Judge Amy Jackson sided with the FDA, finding that the agency did not depart from its precedent in approving the generic medicine and that the decision that the active ingredient was the same was proper.

"Its approval of the drug did not constitute an arbitrary departure from agency precedent, and its determination of active ingredient sameness was not arbitrary and capricious, an abuse of discretion, or otherwise not in accordance with the law," she said in a 33-page ruling.

In August 2010, another judge refused to grant a temporary restraining order against Sandoz and Momenta marketing the generic drug.

Lovenox, which is a type of heparin and primarily used in hospitals, had been one of Sanofi's top-selling drugs with annual sales approaching $4 billion for the French drugmaker before the generic began to be sold in the summer of 2010.

"Sanofi is disappointed that the court has ruled in favor of the U.S. Food and Drug Administration regarding the abbreviated new drug application (ANDA) for a generic enoxaparin," the company said in a statement. "We are currently considering our legal options."

Sanofi could appeal the ruling.

The case is Sanofi-Aventis v. Food and Drug Administration et al, No. 10-cv-1255, in U.S. District Court for the District of Columbia.

(Reporting by Jeremy Pelofsky)

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