Nitroglycerin is a vasodilator which relaxes the sphincter muscle and allows the fissure to close and thus to heal, is my understanding. Diltiazem does the same, and without the side effect of headaches that nitro has.

I am not sure on this one - I have times when this goes on (in fact - this happened for about 2 days earlier in the week) - but then if I watch what I eat, lots of clear broths, etc. etc. - it goes away and I am ok.  Have had this last up to about a week max and other than ointments, I just stay home and ride it out.  Over the years with the pouch - this has probably happened to me on less that 2 percent of days? 1 percent?  Not sure.  When it happens, it hurts terribly and yes - feels like knives coming out and is so incredibly painful.  I believe this time it was caused my some coconut that I did not know was in some candy I was eating...that has caused it before.  But, other unknown causes too.  So sorry you are dealing with this - it is awful.