PGE-1, aka alprostadil, is the ingredient in Caverject that causes aching in about 50% of the men who use it.
The same drug is found, in lesser amounts, in trimix. More men tolerate trimix than Caverject.
Bimix, which some find not to be as consistent as the first two mentioned, does NOT contain the PGE-1/alprostadil and no one (that I have heard of) has aching from that formula.
I have both trimix and bimix and so far have had similar results with both....but with moderate aching from the trimix.