Septrin dosage advice please

Hi,
I'd be incredibly grateful to anyone who could help me please.

My rabbit, Ginger, has had mild recurrent snuffles since about last July. Our vet prescribed him Baytril which worked to start with for a few days, but the snuffles came back almost straight away. It became less effective the more courses he had (altogether he had two 10-day courses and two 20-day courses) until it wasn't having any effect at all. I read a bit online and also asked a local rescue for advice, which resulted in me taking him to a different practice where there's a vet who specialises in rabbits. She prescribed him a 10-day course of Septrin which worked much better and Ginger was clear of sneezes for almost two months.

Unfortunately, he has started sneezing again so I took him back to the vet today. I asked to see the rabbit specialist but when I got there she wasn't available for appointments and he saw a different vet, who didn't seem particularly confident dealing with rabbits. To begin with she didn't seem to have heard of Septrin, but after asking the rabbit specialist for advice she prescribed Ginger another 20-day course.

The trouble is, I'm really worried about the dose she prescribed. When Ginger had his first course of Septrin he had the paediatric suspension and he was prescribed 0.35 ml per day. The vet didn't have any of the paediatric solution in stock today, so she prescribed him the adult suspension instead. After consulting a book, she said the adult solution was weaker than the paediatric suspension and she prescribed 2.25 ml per day.

When I got home it hit me just how much higher this dosage is than his previous dosage and I looked Septrin up on the Internet. Everything I've found says that the paediatric suspension is 40/200mg whereas the adult suspension is 80/400mg - which looks to me to be twice as strong!

I'm really confused. I'm worried about phoning the vet and questioning the dosage in case I'm being stupid (I think they already found me a bit awkward) and I'd like to get the course started as soon as possible but I'm also worried about giving Ginger a dose that much stronger than what he was prescribed before.

Does anyone have any experience of using Septrin please? If so, what do you think of these dosages?

If it helps, Ginger weighs 1.2kg.

I'd be so grateful for any help!!!

Thank you!!!!!!

The adult version is always stronger than the paediatric one and you are right it is twice as strong. There are two active ingredients which is what the 40/200mg is about, there's 40 mg of one and 200mg of the other per 5 ml of suspension. You would need to give half the dose of the adult one to give the same amount of drug. I would give the equivalent of the dose you were told to give last time and ring the vets tomorrow.

Edit: there are some old threads about septrin dosage if you search.

Thank you! That's pretty much what I'd gathered, so it's a relief to have you confirm it. I'll call the vet's tomorrow.

I really appreciate you taking the time to help - thank you!

You're welcome. Based on the other threads I found the dose you were given last time was quite low but there may be a good reason for it, and the new dose was very high given the concentration. Hope your bun's soon better.
There is some info here:
http://wildpro.twycrosszoo.org/S/00Chem/ChComplex/Sulphonamides.htm

Trimethoprim/sulfamethoxazole 40 mg/kg orally twice daily for seven days. As an antibiotic or as a coccidiostat. Note ""Co-trimoxazole" human formulation is available as a human paediatric syrup. (B600.4.w4)"

which would fit with what a a vet posted on a previous thread "Reported doses range from 15mg to 48mg twice daily and the dose I (and most other vets) use is 30mg/kg twice daily."

Wow, that's fantastic information. I'm so grateful - thank you!!

Just an update - the first time I spoke to the vet yesterday, she said she had checked her calculations and was sure the were right but that she'd check with her colleague for advice and get back to me. She called back and left a message saying she had checked 'all the books we have' and thought the dose was right, but it was very difficult to calculate and she was confused so she'd get back to me again later. Finally she called back to say she'd checked with a specialist exotics vet and there was nothing wrong with the dose she'd prescribed, but a 'better' dose would be 0.42ml, especially if he might be on antibiotics long-term.
Apparently the reason for the confusion was that none of her books had dosages for Septrin, due to it not being licensed for rabbits, so she'd calculated the dose as if she was giving the two component parts (trimethoprim and sulfamethoxazole) separately.
I'm going to try a different vet next week, as I really want to make sure Ginger's condition is managed as effectively as possible and I want to find someone who has the expertise to do that.
Thanks again so much for your advice. Ginger hates taking medicines via syringe and is a pain when it comes to doing it so, even if the higher dose wouldn't have hurt him, I'm glad I didn't have to try gettng that much medicine into him unnecessarily.

You could start a post in rabbit chat asking for a vet recommendation in your area. We put meds on bitesized shredded wheats, much easier. Thanks for posting an update, I was wondering how you'd got on.

Thank you! We've used banana occasionally for administering medication, but when it wasn't having the effect we'd hoped we worried in case that was because we weren't administering it properly, so started syringe feeding again.
Another forum member has strongly recommended a specialist exotics vet in Birmingham and I'm taking Ginger to see her this evening, so fingers crossed! Thanks again for all your help.

How did you get on with the new vet?

Really great, thanks! She really seemed to know her stuff and even drew diagrams to illustrate. She doesn't want to prescribe anything until Ginger has had a swab test and x-rays to determine the cause of the snuffles, which is what I've wanted for ages but no other vet has seemed keen to do it. He's going in for the tests of Friday so hopefully we'll get somewhere after that. She asked me to bring his friend Hettie to stay with him, instead of me having to ask her if she could stay, which I also found impressive.
Thanks again for everything!

That's brilliant news! :thumb: