Herbal medicine has been used for millenia to improve sexual stamina and vitality. In this study, investigators looked into how one of the herbs, epimedium, changed rat sexual behavior. They found that male rats given epimedium had more than twice as many ejaculations, much less recovery time between ejaculations and their libido went way up.
 
Though it is generally a safe herb in small doses, there are traditional contraindications to using this herb. Consult an herbalist if you are considering using this herb in therapeutic doses or for longer term.
 
J Ethnopharmacol. 2007 Aug 19; [Epub ahead of print]. Effect of lipid-based suspension of Epimedium koreanum Nakai extract on sexual behavior in rats. Makarova MN, et al.