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