How is Macsoralen used for the treatment of vitiligo?

The brand name is Macsoralen which contains a medicine called methoxsalen. It can be taken by mouth or applied to the lesion in vitiligo. The dose is 20 mg with food or milk 2 hours before measured doses of UV light or sunlight. When used as lotion: 1:10 dilution to be used and expose to measured UV light once a week.