just yesterday I bought a pack of Trojan condoms with spermicidal lube. How effective can those be? and how does it work exactly?
There's been a lot of dispute how effective the spermicide is.
There's no doubt the stuff they put in the lube will kill sperm in the test-tube. The idea is that if the condom breaks the spermicide will add another layer of protection, but there is dispute as to how much contact there would be in that situation between most of the sperm and the spermicide - whether it would be extensive enough and for long enough to kill most of the sperm.
Spermicide is presumably better than nothing, though.