Study participants received the following in randomized order with a minimum 7-day washout period between treatments : placebo at 0 hours and GEn 1200 mg at 2 hours ( GEn 1200 mg group ) , placebo at 0 hours and GEn 6000 mg at 2 hours ( GEn 6000 mg group ) , placebo at 0 and 2 hours ( placebo group ) , moxifloxacin 400 mg ( active control group ) at 0 hours , and placebo at 2 hours ( moxifloxacin group ) .