if you're looking for something nonpsychoactive, according to
this article, ambrein, panax ginseng, and cantharidin are proven to increase libido. also, i don't mean to be
that guy but humans don't enter estrus, as females can be sexually receptive at any point in our hormonal cycle. ik you meant increasing libido but i just wanted to clarify..
if you're looking for a drug specifically, 4mmc is good. meth does it for most people as well.