on ol act one ▁and ▁cy pro ter one ▁ac et ate . ▁Similarly ▁to ▁nil ut am ide , ▁b ical ut am ide , ▁and ▁en z al ut am ide , ▁fl ut am ide ▁cross es ▁the ▁blood – bra in ▁bar rier ▁and ▁ex ert s ▁central ▁anti andro gen ▁actions . ▁ ▁Fl ut am ide ▁has ▁been ▁found ▁to ▁be ▁equal ▁to ▁slightly ▁more ▁pot ent ▁than ▁cy pro ter one ▁ac et ate ▁and ▁substantial ly ▁more ▁pot ent ▁than ▁spir on ol act one ▁as ▁an ▁anti andro gen ▁in ▁bio ass ays . ▁This ▁is ▁in ▁spite ▁of ▁the ▁fact ▁that ▁hydro xy fl ut am ide ▁has ▁on ▁the ▁order ▁of ▁ 1 0 - fold ▁lower ▁aff inity ▁for ▁the ▁AR ▁relative ▁to ▁cy pro ter one ▁ac et ate . ▁H ydro xy fl ut am ide ▁shows ▁about ▁ 2 - ▁to ▁ 4 - fold ▁lower ▁aff inity ▁for ▁the ▁rat ▁and ▁human ▁AR ▁than ▁does ▁b ical ut am ide . ▁In ▁addition , ▁whereas ▁b ical ut am ide ▁has ▁an ▁elim ination ▁half - life ▁of ▁around ▁ 6   days , ▁hydro xy fl ut am ide ▁has ▁an ▁elim ination ▁half - life ▁of ▁only ▁ 8 ▁to ▁ 1 0   h ours , ▁a ▁roughly ▁ 1 7 - fold ▁difference . ▁In ▁accord ance , ▁at ▁dos ages ▁of ▁ 5 0   m g / day ▁b ical ut