Adds details throughout

March 30 (Reuters) - The U.S. Food and Drug Administration has approved a higher-dose version of Biogen's BIIB.O drug for a rare genetic disorder that causes progressive muscle weakness, the company said on Monday, offering patients a potentially more effective option.

The regulator had declined to approve the company's application last year, seeking updated technical information.

The new regimen, which will be available in the U.S. in the coming weeks, uses two 50 milligram initial doses given 14 days apart, followed by a 28 mg maintenance dose every four months, compared to the current standard dose of 12 mg, Biogen said.