So many spaniels end up with heart problems...it really is a sad thing!
Before changing any dosage of medication for your dog, you really need to speak with your veterinarian. I can only imagine the frustration of dealing with a diurectic in a pet, but your veterinarian obviously thought the medication was needed at that dosing level.
You can, though, post this question in the Ask A Vet Expert forum and get some opinions from veterinarians across the country. They would be able to help guide you with information you can share with your veterinarian at home and questions that you might ask your veterinarian.
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