Last summer when our angel Chris was having a hard time, the internist
put him on Spironolactone in addition to his Lasix. Some of the folks
here gave their cats Hydrochlorothiazide (HCTZ).
You might want to ask the vet about giving injectible Lasix at home.
When my angel Sweetie was in her bad times, my vet gave us injectible
Lasix. It works better and faster than the pills. The dose is
dependant on the cat's weight, so the vet would have to tell you what
it would be for Rudy.
I hope he'll be okay through the weekend.
Sending healing thoughts,
Carol and Snowball and the gang