Don't know if this will make any sense to you but I have had a similar reaction to amoxicillin ...makes me kind of punchy
Side-effects are as those for other beta-lactam antibiotics. Side-effects include nausea, vomiting, rashes, and antibiotic-associated colitis. Loose bowel movements (diarrhea) also may occur. Rarer, but patient-reported, side-effects include mental changes, lightheadedness, insomnia, confusion, anxiety, sensitivity to lights and sounds, and unclear thinking. Immediate medical care is required upon the first signs of these side-effects.
I copied and pasted that from Wikipedia.... It's side-effects for human use so I don't know if that transfers to dogs....
The side -effects for Rimadyl, short time use is gastric upset....
I hope Bre feels better soon.