BNT ointment

Re: BNT ointment

Alex Allen — Fri, 09 Mar 2012 12:10:07 GMT

Aminoglycosides are routinely used in otitis externa in both veterinary and human worlds - eg Framycetin (Canaural) and Gentamicin (EasOtic and Otomax). Neomycin is also used orally for lambs vs coliforms. The important fact is this family of antibiotics is negligibly absorbed through either skin or gut. As a result topical use of these concentration dependant antibiotics is very effective as very high concentrations / doses can be used quite safely.

This contrasts considerably with their use IV or IM where the dose is a minute fraction of the topical dose due their nephrotoxicity, cochleotoxicity and vestibulotoxicity. Unfortunately we are routinely taught from generic pharmacology texts where they systemic use is all that is discussed when in practice it is very rarely the way we would use this class of antibiotics. Culture and sensitivity testing for this family is often based on systemic drug concentrations and has little resemblance to the concentrations used topically - beware the "resistance" report as this maybe nonsense at the concentrations you'll be using topically - also relevant for some other classes of antibiotics.

As the article points out anything can provoke a local neuropathy which can manifest as head tilt, aniscoria, Horner's etc. Both sympathetic and facial nerves run through the tymp bulla and are vulnerable. Inflammation from infections or chemical irritation (alcohols, acid cleaners etc) can cause these nerves to malfunction - some baterial toxins could also trigger a neuropathy and a simple saline flush may agitate the nerves resulting in adverse effects. Typically these local neuropathies are temporary and can improve as the otitis media resolves.

Inner ear toxicity is a different issue and certain drugs / chemicals are known to damage the cochlea or vestibular apparatus - damage maybe permanent so the potential for treatments to induce ototoxicity must be carefully assesed prior to therapy. Inflamed middle ear structures may compromise the barrier between middle and inner ear structures making some compounds more likely to cause toxicity when instilled into the tympanic bulla.

Re: BNT ointment

John Rimmer — Fri, 09 Mar 2012 09:52:48 GMT

One use for the product Triz EDTA, yes. It's the general use as a "cleaner" that annoys me. It doesn't contain a cleaning agent. And there are cleaning agents on the market which contain EDTA (Epi-Otic, Surosolve) - so in most cases, best to use a CLEANER with EDTA rather than EDTA alone. But yes, in this case, where you want to put as few chemicals in as possible, TrisEDTA MAY be better.

Re: BNT ointment

John Rimmer — Fri, 09 Mar 2012 09:50:19 GMT

[quote user="Mark Hedberg"]

The fact that it's a westie suggests that the possibility of atopy should be investigated.

[/quote]

I've hear a number of dermapods say that WHWT are predisposed to pretty much all skin diseases, i.e. atopy in westie skin case population same as atopy in general skin case population.

Re: BNT ointment

John Rimmer — Fri, 09 Mar 2012 09:47:01 GMT

[quote user="Michael Woodhouse"]

[quote user="John Rimmer"]

Hmm are there any derma pods on here to advise? There was an article in this week/last week VT on otitis whereby a paper was quoted where gentamicin was instilled in the middle ear and no ototoxicity resulted, so would seem a good antibiotic to chose. Think article also stated that anything was potentially dodgy with ruptured TM though, including water.

[/quote]

So an aminoglycoside is ok with known CN toxicity, but water was bad?

[/quote]

Known toxicity WHEN SYSTEMIC, not locally. The point about the water was "anything in the middle ear is bad" I think, but possibly gentamicin no worse - LOCALLY - obviously gentamicin ototoxic when systemic.

Re: BNT ointment

Mark Hedberg — Fri, 09 Mar 2012 09:33:27 GMT

[quote user="Oli_J"]

Thanks for the input. I currently have a Westie with pseudomonas OE in the left ear, ruptured tympanic memb, that has not responded to 3 weeks of oral baytril, pred and saline flushes BID at home. The ear was initially cleaned under GA when the swab was taken, and admittedly this dog hates the ear being touched in the surgery but the O's say they have been getting on OK with cleaning at home (has to be sedated for otoscope exam due to temperament). The inflammation has improved but the discharge has built up significantly again since the first cleaning. Was sedated again on Tue for repeat cleaning and another swab for which results are pending. I'm thinking he will need some topical therapy to prevent the ear filling up with pus and wax again and since I cannot locate the above ointment am considering Tris EDTA with baytril inj and dexadresson added to it. The 'recipe' I found on VIN involves 120ml tris EDTA + 2ml of 2% dex + 6ml of 100mg/ml large animal injectable baytril. Any thoughts?

[/quote]

Yes; a significant percentage of dogs with atopic dermatitis have chronic otitis as a presenting symptom; the constant irrititation in the ear apparently predisposes them to infection. (Source: Atopic dermatitis symposium, lecture by Dr Claude Favrot, Barcelona 2011.) The fact that it's a westie suggests that the possibility of atopy should be investigated. How old is the westie?

Re: BNT ointment

Andrew Kent — Thu, 08 Mar 2012 22:48:44 GMT

Good plan, I would use Triz EDTA (now a dechra product) with enrofloxacin (I usually use up to 10ml of 5% baytril) and dexamethasone (up to 5ml of colvasone). There are some alternative antibiotics if needed (eg ticarcillin) but find this works in most cases. You may well need to use it for a number of weeks.

Re: BNT ointment

Oli_J — Thu, 08 Mar 2012 22:39:01 GMT

Re: BNT ointment

Michael Woodhouse — Thu, 08 Mar 2012 21:13:05 GMT

[quote user="John Rimmer"]

[/quote]

So an aminoglycoside is ok with known CN toxicity, but water was bad?

Re: BNT ointment

John Rimmer — Thu, 08 Mar 2012 20:34:58 GMT