Fluoroquinolones and the Feline Retina

A short while back someone emailed me to ask what my recommendations are when it comes to using fluoroquinolones in cats with respect to the potential for retinal damage and blindness. She had been discussing the issue with colleagues in her practice and there was no consensus which was not helped by the fact that the formularies and other book resources they had available did not entirely agree with each other – quelle surprise?!

So I tried to do the right thing and spent some time seeing what I could find in the published literature. The papers that I reviewed are listed below – and I also had a look at Plumb’s Veterinary Drug Handbook – and this is what I replied to her:

“So you definitely need to bear in mind the dearth of 'proper' evidence base (you know, prospective randomised controlled ideally blinded studies then a systematic review etc.) when considering issues like this and my comments.
 

Enrofloxacin

From my look through whatever published papers I found, it seems that what we can say at this point in time is basically that any cat could be at risk regardless of dose or route of administration. 

With that said, some things may be noteworthy:

The risk seems higher at higher doses - this would suggest a dose-dependent effect but...
There have been reported cases in which manufacturer recommended doses have been used. It is not clear whether:

  • This is still a dose-dependent effect and these cats were somehow more susceptible (e.g. due to altered metabolism due to age), or
  • The response is actually non-dose dependent (idiosyncratic), or
  • There could be elements of both types.

Reports exist of cats suffering retinal damage after both intravenous and oral use.
Longer courses may pose more risk - but again I know of cases in which it occurred acutely.

Other fluoroquinolones

As far as marbofloxacin, I have not come across any published literature of retinopathy as yet.
Apparently the FDA has had some anecdotal cases reported to them of cats becoming blind but this is too unclear to attribute cause-effect relationship.

Out of interest one nasty experimental study in healthy cats I found with pradofloxacin (which may find itself onto practice shelves) given at very high doses (6 and 10 times recommended doses) did not report any adverse retinal effect but again this is not brilliant clinical evidence.

What do I do at the moment?

With the information I know on this my clinical approach when treating in-patients tends to be to give marbofloxacin at a conservative dose (from memory 2 mg/kg IV q 24h) if I want to use a fluoroquinolone and unless I have a reason not to use marbofloxacin vs. enrofloxacin.

There is some (albeit less evidence) that marbofloxacin works against mycoplasmosis and in those cats that we are treating empirically while awaiting PCR results for this agent I tend to use marbofloxacin. A lot of these cases are anaemic and poorly tolerant of stress and I don't like pilling them with doxycycline then syringing water down after. So oral doxycycline if they take it well, ideally in food etc., otherwise IV marbofloxacin until the results are back.

If I have to use enrofloxacin I would either give it slow IV diluted or PO, usually 5 mg/kg q 24h; it has been reported to be usable at 2.5 mg/kg q 12h and this may be safer from a retinopathy point-of-view. I have not explored this though. It is a concentration-dependent antibiotic so I would want to be sure this split-dosing is shown to be effective before considering it.

Overall I would aim for conservative dosing and as short a course as possible. AND as always only use these agents based on adequate clinical proof of their need (empirical antibiotic use – no no...empirical fluoroquinolone use - even bigger no no!).

Hope that helps,

Shailen”

Really interested to know if anyone knows of any additional information on this or has a different interpretation of what information is available.

Papers I read

Dowers KL, Tasker S, Radecki SV, Lappin MR. Use of pradofloxacin to treat experimentally induced Mycoplasma hemofelis infection in cats. Am J Vet Res 2009. 70(1):105-111.

Ford MM, Dubielzig RR, Giuliano EA, et al. Ocular and systemic manifestations after oral administration of a high dose of enrofloxacin in cats. Am J Vet Res 2007. 68(2):190-202.

Gelatt KN, Van Der Woerdt A, Ketring KL, et al. Enrofloxacin-associated retinal degeneration in cats. Vet Ophthal 2001. 4(2):99-106.

Messias A, Gekeler F, Wegener A, et al. Retinal safety of a new fluoroquinolone, pradofloxacin, in cats: assessment with electroretinography. Doc Ophthalmol 2008. 116:177–191.

Wiebe V, Hamilton PDP. Fluoroquinolone-induced retinal degeneration in cats. J Am Vet Med Assoc 2002. 221(11):1568-1571.
Plumb's Veterinary Drug Handbook - Online Edition