I’m glad you went in and found the problem!
When my bun had a jaw abscess I believe I did penicillin shots every other day for 6 weeks (but I can’t quite recall).
The first few will be stressful, but you will get the hang of it. Deep breaths! My bun barely noticed the shots, it was easier than syringe feeding for sure. the first time I gave one I poked through too far and the medicine ended up on his fur. That’s probably the most stressful thing because you have to clean it off really well (if they ingest it it’s bad news). Have some water and paper towels on hand and it will be ok though.
I found it helped to make a kind of pyramid shaped skin tent by pinching with my thumb and 2 fingers so there was a nice pocket to inject in (vs just pinching with 1 finger and my thumb).
If you poke through and need to re-poke because you aren’t happy with the position, use a new needle (they dull really fast, so the second poke will be difficult if the needle is a little dull already). I ended up moving the injection site around basically all over my bun’s shoulder area. Over time if you use the same area it starts to get a little thickened due to scar tissue and harder to do the injections.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.