Wyeth sues FDA, seeking halt to generic Zosyn

* India's Orchid had won approval for generic

* Wyeth shares off 0.4 percent

NEW YORK, Sept 23 (Reuters) - Wyeth WYE.N has sued the
U.S. Food and Drug Administration, claiming the agency's
approval of a generic version of the drugmaker's blockbuster
Zosyn antibiotic endangers patient health.

India's Orchid Chemicals (ORCD.BO) earlier this month won
approval to market its generic form of Zosyn, which had about
$1.3 billion in sales last year.

In its suit filed in the U.S. District Court for the
District of Columbia, Wyeth said the generic version of Zosyn
is based on a formulation that Wyeth no longer markets.

Wyeth's current formulation includes two "functional
inactive ingredients ... that are critical to its compatibility
with other frequently used drug products," the suit said.

Wyeth claimed the FDA's approval of the Orchid version was
unlawful and requested a temporary restraining order or an
injunction ordering the agency to withdraw or suspend its
approval of Orchid's application.

An FDA spokesman said the agency does not comment on
ongoing litigation.

Wyeth agreed earlier this year to be bought by rival Pfizer
Inc (PFE.N).

Wyeth shares were down 0.4 percent at $48.37 in morning
trading on the New York Stock Exchange.
(Reporting by Lewis Krauskopf, editing by Matthew Lewis)