U.S. clears less often use of Novartis bone drug

* US approves single dose of Reclast over two years

* Some 22 mln women in US have osteopenia

ZURICH, June 1 (Reuters) - U.S. regulators have approved Novartis AG's (NOVN.VX) Reclast to prevent osteoporosis in postmenopausal women with less frequent dosing, the Swiss drugmaker said on Monday.

Reclast, known as Aclasta outside the United States, is already approved in both the U.S. and Europe as a once-yearly infusion for the treatment of postmenopausal osteoporosis.

The new approval is for a single dose over two years to treat ostopenia, or low bone mass, which can lead to osteoporosis.

Approximately 22 million women in United States have osteopenia, or low bone mass, putting them at increased risk of fractures of hip, spine and wrist. (Reporting by Sam Cage; Editing by David Holmes)