What would happen if a woman takes Viagra? Just as Viagra helps men with erectile dysfunction by increasing blood flow to the penis, it causes blood to flow to women's sexual organs, potentially increasing sensitivity. How long does it take for female Viagra to work? about four weeks Number three, with Viagra, men just take it when they want to have sex. Women have to take flibanserin every day, and it takes about four weeks to begin to see an effect. Is Lady Era FDA approved? On August 18, 2015 the FDA approved Addyi (Flibanserin) for the treatment of premenopausal women with low sexual desire that causes personal distress or relationship difficulties. BUY TO KNOW MORE.