I would suggest swapping it for
Benazepril (ACE Inhibitor), or adding it to the Amlopidine (needs a vet to consider this combination).
Creatinine at 4.1 is high. Is it still at 4.1 now? Two days of fluids probably aren't enough. In such circumstances, I would want a minimum of 3 days IV fluids, and possibly 5days if improvements were not satisfactory. The fluids flush out the toxins, which is important as otherwise, they start damaging the kidneys, and then the kidney issues deteriorate.