Has anyone ever had your horse have a reaction to pentosan? I gave it to three horses on Wednesday and on Thursday one had a knot where I gave it and the other two had some very slight swelling. Today the horse with the knot no longer has the knot just swelling on that side of the neck and near the top of the neck. The other two have swelling a couple inches long with heat. None are running a fever all eating and drinking like normal. They act normal besides looking a little stiff and drained of energy.

If it was made by Racehorse Meds or another compounder they don't have the quality control that regular pharmaceutical co. Have. It may not have been mixed well or may not have proper/correct ingredient level.

I bought it from my vet and have used several doses out of this bottle. This is the only time something has happened. 

If it came for a vet then I would give the lot number to him and talk to him about it. 3 out of 3 reactions isn't normal. 

I have had this in the past when using pentosan from racehorsemeds.

I did find if I pushed it slower I did not have an issue with swelling at the injection site.

The pentosan from RHM is supposed to be given IV. I've been using & giving it this way for several years with no problems at all. Was giving IM before this with neck swelling several times.

I had my gelding on it a little over a year then all of a sudden, same bottle, he swelled and was super sore,, thought I just stabbed him weird or something. Next time around, same things, same bottle but that was the last dose til the next month so ordered a new bottle. New bottle came and same thing,, got rid of the bottle and got a new one,, same thing so I took him off of it and now Im scared to use it.