Medical question to vet students from a med student

[aykau777]

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Hey guys! Im a Med student who loves his Cavalier King Charles Spaniel 🙂 I went recently to my vet in Puerto Rico and he told me that my dogs Interceptor dose was on back order and that probably would not be available for a few months. Naturally I call other vets in my area and they all told me the same thing. Because of this I became curious and I research other alternatives for my dogs heart worm medication. That's how I became aware that Interceptor is a macrolide. I was kind of surprised since I never heard or read that a macrolide can be used as an anti-helmintic since we used it in human medicine to interfere with protein synthesis @ the P site of 50S ribosome subunits of bacteria. Plus I wonder if Interceptor could create bacterial macrolide resistance in pets If it is use on a monthly basis. It's happening on humans already Here comes my question 😕 Why is a macrolide such as Interceptor (milbemycin) preferred by lots of vets? Why am I wrong for being skeptical about its use?

Thanks for the help. I don't mean to be a smart ass 😳 Im just looking for a medical explanation from the vet students since I have no access to vet books or vet journals or have any knowledge of vet medicine.


ohh...I change to Iverheart. Pharmacologically it made more sense to me

 

[sunshinevet]

So I don't have an awful lot of brain power right now (night shift has fried it lol) but heres some basic stuff.

The avermectins and the milbemycins have very little antibacterial action. Yes they are macrolides but that is a very very large group and not all of them work the same - not all of them are antibiotics. Basically they work by leading to hyperpolarisation of the nerves in invertebrates, leading to an inability to signal and death.

I'm not sure why Iverheart would make more sense to you - milbemycin is very closely (chemically) related to ivermectin and its mechanism of action is pretty much the same, so I don't know why you would favour one over the other. Ivermectin is thought to be more effective against heartworm though.

The interceptor shortage is worldwide atm - very annoying!

So to answer your questions - macrolides are prefered by vets as they have a broad spectrum action against a lot of worm species, and they tend to be very safe (there are some exceptions but they don't matter here). You're wrong to be skepical about its use as the macrolides we are using in this instance have a different MOA to the ones you are thinking of.

Good on you for being proactive and looking into aspects of your dogs care. Just remember that not everything that is used in humans applies to animals the same way, so always check it with your vet. 😉

 

[aykau777]

HOLA : ) more questions he he......
Have you ever read in a Vet Journal about negative consequences of having some antibacterial action? Is there evidence of bacterial resistance since its given monthly to pets? My question comes from the fact that Cavaliers are prone to mitral valve disease and a most mitral bacterial vegetations are treated with macrolides. mmm "well at least on humans" : P. And since I'm using one monthly with some antibacterial action. Wouldnt this be bad for breeds with risk for mitral valve disease on a long term?

I liked iverheart because its also has Pyrantel and Praziquantel. It make more pharmacological sense to me since it has a wider antihelmitic spectrum than Interceptor. It also gives Me protection considering that my dog sleeps in my bed and poops inside my house.

 

[sunshinevet]

Nope, never read about it, thought about it or heard about it.
When we say some antibiotic action, they essentially mean none...
I guess its kind of like saying "if i take azithromycin will it get rid of my worms?" Nope because it doesn't work like that. Yes it is a macrolide but they are very different groups of macrolides. We use macrolides extensively as antihelminthics in many species.

If your cavi develops mitral valve disease its unlikely to be due to bacterial vegetation and more likely to be genetic so I wouldn't be concerned - but thats my 2 cents. So I'm going to go with "no, I don't believe its an issue". But honestly if your that concerned you really need to talk this over with your veteriarian who knows your dogs history.

I understand the greater broad spectrum activity of iverheart, I took it as you didn't feel milbemycin was a good choice as it was a macrolide so I was confused as to why you were happy with ivermectin given how similar the two drugs are.

Also I'm pretty sure far more dogs have died of heartworm disease than bacterial endocarditis (yes that is entirely anecdotal but pretty sure its true lol!) so I would be less concerned about antibiotic resistance and more concerned about getting the best protection possible 🙂

 

[aykau777]

Thanks for the explanations. You have been very helpful. Why is interceptor better that iverheart? What are the medical reasons?

 

[bunnity]

Sunshinevet is right on the money... a macrolide just means it has that ring in its structure, but not all macrolides are antimicrobials (if you look up the wiki article it looks like some are immunosuppressants too, although I have never heard of them used for that in vet med).

We use the protein synthesis inhibitor / antimicrobial ones too!

Ivermectin and milbemycin have extremely similar structures and MOA. Ivermectin just has an extra deoxy-something-or-another group that milbemycin doesn't have.

 

[Tuttley]

My question comes from the fact that Cavaliers are prone to mitral valve disease and a most mitral bacterial vegetations are treated with macrolides.

Wouldnt this be bad for breeds with risk for mitral valve disease on a long term?

Cavaliers are prone to endocardiosis, not endocarditis. It is caused by collagen degeneration of the valve and is non-inflammatory and non-bacterial in aetiology.

The previous posters are right about Milbemycin not being antimicrobial, despite being in the broad macrolide group (which is grouped so based on structure, not function of the drug).

From a Cavalier loving and owning vet student 🙂

 

[alliecat44]

P.S. When dogs DO get bacterial endocardITIS, it is extremely rare--and most commonly affects the aortic valve. 🙂