Lethargy/weight loss in older male cats - medication questions

[spazsmom]

Spaz, almost 15, was recently diagnosed with a urinary tract infection and was on Bayril for 5 days before the vet and I took him off from it. The vet overprescribed it according to his weight (22.7 mg. per day; it should have been half that amount according to Dr. Lee's calculations). He got extremely ill from it and had to be given IV fluids on Monday. He weighed 6 pounds before taking it, and now he is down to 5 pounds. He has been on Prednisone (2.5 mg twice a day) since Wednesday, and is still not back to himself. How long does it take for the Baytril to get out of his system and when will the Prednisone start kicking in?

[Dr Lee]

I will try to help you out but I want to be clear that I do not know that your vet overprescribed baytril. I always have concerns regarding the use of baytril in any cats but older cats in general. With that said, I have and do use baytril in some older feline cases and occasionally go higher then 5mg/kg/day. It is an individual case management and should be based on some evidence for its use.

How long is baytril in the system?
According to Plumb's Drug handbook, "The approximate elimination half-lives in various species are: dogs 4-5 hours; cats 6 hours; sheep 1.5-4.5 hours; horses 5-6 hours, turtles 18 hours; and alligators 55 hours."

However baytril is eliminated through both renal and non-renal mechanisms. If any of these mechanisms are not functioning 100% then the half live will be prolonged. Estimating new half lifes on individual patients is very subjective.

Quick definition - elimination half life is the time that it takes to eliminate half of the medication in the system.

Also is your cat on prednisone or prednisolone? Also why is your cat on the steroids?

Just a note on prednisone. Prednisone is an inactive form that must be actively transformed into prednisolone, an active metabolite. There are some species such as cats who are thought to be deficient in this tranformation. This is out of the North American Companion Animal Formulary: "Use prednisolone for cats; prednisone may not be effective."

When should it take effect? Steroids typically have a rapid onset of action. I am here to try to help answer questions but there is a huge difference from hearing descriptions from people on pets.ca and actually being the veterinarian on the case with the patient in front of him or her.

[Dr Lee]

One of the reasons I am asking about the prednisone or prednisolone with regard to your pet is that your cat was placed on baytril presumably to address a bacterial infection. Steroids can suppress immune systems and allow infections to worsen. Is there another antibiotic being used concurrently with the prednisone? Sorry, I feel like there is a lot of information on this case that I am not seeing. Can you provide more information?

[Dr Lee]

How is Spaz doing? Any news? Is he doing better?