Medical marijuana does this.
I'll be honest, as a consumer of cannabis (it's 100% legal where I am, and it has been highly beneficial for me in terms of pain management) I don't think this is true. I've never heard of cannabis affecting sex drive, and to be perfectly honest personal experience suggests otherwise.
On the other hand certain anti-depressants and anti-anxiety medication does do this. I take citalopram (the generic form of Celexa) daily, have for about a decade now.
I'm not trying to be vulgar or provide too much information. But I assume that we are all adults here and can discuss normal things in a mature way.
I know that we're living in a time where cannabis is frequently touted as a panacea, and while I totally do believe in the medical benefits of cannabis (as already mentioned earlier), it doesn't solve everything, and I don't even think it's necessarily going to be helpful for everybody.
I don't think there's a good reason to seek out chemical castration. Rather, as Christians we should be mature and frank, compassionate and kind in our discussions of things such as human sexuality. And good pastoral work is done that helps us with preaching of the Law to the denial of the sinful disorderedness of our passions, which also guides us to repentance; and also faithful preaching of the Gospel as we hear of God's mercy and forgiveness. Likewise the Law establishes faithful and just order: That we love our neighbor as our self, that we regard and recognize the humanity in our neighbor--created in the image and likeness of God.
When we lust for someone, we objectify them, we deny their God-given humanity. And in this way we cause injury, as we seek to impose ourselves and our desires on the other--and from this flows all manner of many other sins.
So when the Law preaches that we should love our neighbor, and we are not loving our neighbor if we objectify and lust after another; then our flesh might be mortified by the Law. For the Law says "Do this" and we don't do it, as the Apostle says, "The good that I wish to do, I do not do".
But the Gospel is always there to catch us, because "God demonstrates His love for us in that while we were still sinners Christ died for us".
And in this peace and reconciliation from God, the Law while condemning us in our sin no longer destroys us, but in the forgiveness of the Gospel the Law becomes the open invitation to live and to love our neighbor. So that when I fail to love my neighbor, I repent; and God forgives me and loves me in the Gospel, and still calls me to love my neighbor.
I believe it is in this way that, by the grace of God, working through faith, by the means of God's Word and Sacrament, that we are being renewed, and invited daily to die to ourselves, and to live for God by loving one another and all our neighbors we come across. And here in the midst of the world, in our struggles, in our carrying our cross as disciples, we also get the joyous opportunity to share the same Gospel that saves us with others. For the grace and love of God that has held us captive to His kindness goes forth out from us, as the Church, into the world.
-CryptoLutheran