Hi Yanna,
Just catching up with yourself and Naomi. Am I correct in thinking that increasing the frequency of administration of ondansetron (Zofran) has been helping her to eat better? It sounds like it from your opening post today, and I'm really pleased for both of you that it seems to be working for you.
IIRC at the moment you are dosing at 2mg TID. If the ondansetron is the 'magic bullet' helping Naomi to eat better then reducing the dose of ondansetron or suspending treatment will likely see her eating difficulties return. Should that prove true then you may need to consider adding ondansetron to her daily maintenance treatment regimen.
With a bit of trial and error, you may be able to identify the minimum dose required (size and frequency) to provide the anti-nausea benefit Naomi needs. The recommendation from Tanya's site for dosing of this medication is as follows:
For chronic nausea in CKD cats, however, many people find a dose of 1mg is fine, but needed at least twice daily, and if that doesn't work, then three times daily. Very occasionally, cats need ondansetron four times a day.
I would start with a dose of 1 mg twice a day, and if you find this is not enough, speak to your vet about increasing the frequency initially, and if necessary, the dose.
Based on my experience managing nausea and appetite issues in my own cats, I find that it is much,
much easier to keep a cat with some bit of appetite eating than to get it to resume normal eating from a standing start. Now that Naomi is at last now eating on her own again (yay!!!) I would be very reluctant to mess with the status quo too much or too fast. For the reason stated above and having been in very similar situations with my own cats, rather than stopping ondansetron completely I would suggest you try reducing the dose size and/or adjusting the frequency of administration to the minimum needed to maintain the anti-nausea benefit to Naomi (essentially the reverse of the process from Tanya's Site above).
Possible downward titration steps to try:
* 2mg TID (current dose, total 6mg/day)
* 1mg TID (total 3mg/day)
* 2mg BID (total 4mg/day)
* 1mg BID (total 2mg/day)
Just as it can take a few days for a cat to derive the full benefit from a given dose of ondansetron, so too it may take a couple of days before one can judge how well/poorly any dose adjustment will work. If at any stage after a dose/frequency change Naomi's eating problems return, even partially, then I'd suggest returning to the previous effective dose straight away so that you don't lose any of your hard-won ground. Once she's stabilised again, try a different dose size/frequency. For example, a reduction to 1mg TID might be less effective than changing to 2mg BID, or vice versa.
I don't see any way round the trial and error, short of a magic wand that would enable our little ones to be able to speak so that they could tell us what works best. I can dream...
Ondansetron is extensively metabolised in the liver. There are caveats about dosing for human patients with hepatic impairment on several drug sites but I've not come across any specific warnings about patients with kidney insufficiency.
According to
this article:
Clearance [of ondansetron] occurs by hepatic metabolism (95%) rather than renal excretion.
According to
drugs.com:
Elimination
Metabolism and Excretion: Ondansetron is extensively metabolized in humans, with approximately 5% of a radiolabeled dose recovered as the parent compound from the urine. The metabolites are observed in the urine. The primary metabolic pathway is hydroxylation on the indole ring followed by subsequent glucuronide or sulfate conjugation.
Specific Populations
Renal Impairment: Renal impairment is not expected to significantly influence the total clearance of ondansetron as renal clearance represents only 5% of the overall clearance. However, the mean plasma clearance of ondansetron was reduced by about 50% in patients with severe renal impairment (creatinine clearance less than 30 mL/min). The reduction in clearance was variable and not consistent with an increase in half‑life..
Hepatic Impairment: In patients with mild-to-moderate hepatic impairment, clearance is reduced 2‑fold and mean half‑life is increased to 11.6 hours compared with 5.7 hours in healthy subjects. In patients with severe hepatic impairment (Child‑Pugh score of 10 or greater), clearance is reduced 2- fold to 3- fold and apparent volume of distribution is increased with a resultant increase in half‑life to 20 hours.
[Emphasis mine]
At some stage one has to weigh up risks and benefits of particular treatment options. From the above it seems that ondansetron does not impact the kidneys greatly but I suggest you confirm that with your vet. I couldn't see any caveats or warnings on Tanya's Site.
One thing to consider is that if a cat can't eat enough then that, too, can cause problems for diabetic cats, with or without other comorbidities, because it can interfere with the cat's ability to safely receive enough insulin. Not getting adequate insulin would also carry risks, in particular:
* BG levels not at optimum - higher BG levels can put an additional strain on the kidneys, increase risk of developing UTIs (especially if BG levels creep above the renal threshold) , slow healing from infections in general, and increase risk of organ damage (all of which are of great concern for CKD cats)
* greater risk of problems with ketones - doubly so if cat is neither getting enough insulin nor enough food.
I hope some of the above helps you a little bit.
Mogs
.
