When I get that way, I will spray my anus with Dermoplast (which can sting immediately but starts to numb in seconds). Then I can usually squirt a bit of Preparation H up in there which numbs it even further up, wait about a minute and then try the suppository. The Prep H nozzle is a bit smaller than the suppository, so that might work for your son. Sometimes I am too sore to even do that. Preparation H also makes suppositories that are very skinny compared to Canasa and others, so they are another option to try and let them dissolve for a while before inserting other medicine. Another thing I try coating both the Prep H nozzle and the suppository with hydrocortisone cream. Hydrocortisone helps lower inflammation and helps with lubrication, but I wouldn't use it without numbing first. Anal pain is very intense, and like your son, there are times when you just can't take suppositories because of the pain
. It might be worth trying some Tylenol about an hour before. Another good pain med I've tried is Tramadol. Not sure how old your son is or if he could take it, but it helps take the edge off. Good luck to him--I know this is a difficult thing to deal with!
Jeff