Hi Lydia,
I am not familiar with you or Sid, but Serryn sent me a PM and asked me to drop by. I hope Sid is doing better today.
Yes, my cat Bob was injected IM for all but the first few days he got insulin. It was roughly 10 weeks. He was not on Prozinc, but on PZI. PZI has a shorter duration, so what I can tell you about the timing of his cycles would have to take that into account. My understanding is that PZI normally lasts 8-10 hours while Prozinc's site says 10-14 hours duration.
When I first got here, I mentioned that Bob got IM shots, but nobody told me that it had been done by anyone else. I was told it shouldn't be done, but by that point, I had already been doing it for a month or more, so I just kept doing what I was doing and didn't ask for any dosing advice. I just read a lot and tried to figure out what to do.
My vet had never had anyone shoot IM before, so it was new ground for her. Her reasoning, as I discussed with her after Bob was OTJ, was that due to his condition, and because I would be hometesting and administering sub-q fluids daily, that it was the best option for Bob. She was concerned about the insulin absorption rate if I were to shoot the scruff while flooding the area with sub-q fluids twice a day. She never discussed shooting sub-q in any alternate location, and at this point, I had never given any animal any shot, so I had no idea what I was doing anyway. This was weeks before I found FDMB. So I just nodded my head a lot and tried to pay attention. You may have seen a thread I started in Think Tank about dehydration and if it affects insulin absorption? Nobody really replied much to it, but the whole reasoning behind the question was based on how I treated Bob, and if my vet may have been right or not. After the fact, I was sort of "gee I wonder if it realy mattered?"
What I do know is that after 10 weeks on PZI IM shots, Bob went OTJ. Would he have if I'd done things differently? I have no idea, and I'll never know. I kind of think it was a real ECID thing, which is why I have never suggested to anyone that they do what I did.
After Bob's first few days on PZI, administered sub-q, he got worse. He was diagnosed DKA and required emergency care. The vet told me that in the ER he would have gotten IV and IM insulin treatments, so she felt that if I could do the IM shots at home, it would be best for Bob. The ER costs would have been about $1000 per day, for 2-3 days. I didn't have the money, but told her I would do whatever I could do myself to save my cat. So she kept him for 3 days, at her clinic. I don't know exactly what Bob got or how he got it for those 3 days. On the third day, I went to get him, and she showed me how to shoot IM, and she sent us home with a bag of fluids. He got 200 cc's a day of lactated ringers w/ potassium, and two IM shots of PZI, 12 hours apart, 1u. Oh, the vet apparently felt bad for me due to my lack of money, so she did most of the work "gratis". The invoice was for about $250 for three days of 24/7 care. I love my vet.
What they did at the clinic to make it easier for me was they shaved a "bulls-eye" on Bob's rear legs so that I could see the injection site and see how the needle went in. The shot location was on the big muscle on his rear leg, not the rump, but the next section down. I would equate it to what we call our hamstring muscle. I would lay Bob on his side, grasp the fat part of his leg so that he couldn't move or bend his leg (to avoid him moving while the syringes was still in my hand and in his leg). I was using 1/2 needles, u40 syringes, 29 guage. I pinch the muscle so it was fattest where I'd be sticking in it, stuck it in halfway. The hardest part was drawing the plunger back a little bit to make sure I didn't get any blood. In 10 weeks, I only saw blood one time and had to jab again. It was hard to do that with one hand, but I got good at it. After that, it was just push the plunger and pull it out. The shot process itself was just as easy and quick as an IM sub-q shot. I never had a fur shot using IM. I had his leg held imobile so he couldn't jerk away. (edited)
As far as pain? I didn't see any bad reaction from Bob. Once in a while, he'd chirp or meow softly, but he never acted as if he was in pain. After the shot, I would massage the site a bit, not much, just to distract him more than for any other reason. As long as he got a treat or got fed right after, he was happy. I would alternate legs AM and PM so he never got shot in the same general location twice in a row.
His typical duration was 9 or 10 hours, and his nadir was between 4-5 hours. However, since I only shot sub-q for the first three days of his treatment, I can't compare to tell you if it was absorbed more quickly or peaked sooner with Bob. The largest dose I ever gave him was 4u BID, and he didn't act any differently when I shot 4u than he did when I shot .25u as far as how if felt getting the shot.
I hope this helps, and if you have any questions, I'd be happy to answer them.
Carl