Opiates. Others saying they go forever on them, I don't get that, they just make it hard to get it up and when I do I'm pushing rope.
Benzos don't seem to effect my sex drive either way unless I take enough to get too tired, stims increase it but again make it hard to get it up and give me pencil dick.
I'd imagine psychedelics make it difficult too but I've never tried.
I thought 5 meo dalt was good for a bit of the ol' pumping, I've heard mixed reviews though, but for me I called it 'dalt dick', good times indeed.