It is important to keep up the medication in order to eradicate the bacteria. It’s great that you’re seeing such great improvement already, but you want to make sure that all bacteria are gone before you stop the antibiotics. 2 weeks is not long, many buns need much longer courses of antibiotics.

The risk with stopping the meds too soon is that the bacteria that havent succumbed to the abx yet, will start to multiply once  the abx is out of the system. Then you get a flare-up and have to start all over.

You can give your bun a probiotic if you are worried. There are beneficial bacteria and yeasts that are resistant to antibiotics. It’s still advised to give the daily probiotics a couple of hours before or after the antibiotics.

Penicillin must always be given as injections, never by mouth, just because it’s so hard on the rabbit gut microbiota -if, and that is if – it gets into direct contact with the gut. By giving it as injections it doesnt come into direct contact with the inside of the GI tract.

Agree that you should complete all antibiotics as instructed by the vet, stopping early leads to antibiotic resistance and can create larger issues for you down the road. Is your bun showing any signs of GI stress? Such as smaller poops, gas pain, etc?

Penicillin given orally is very dangerous, but if injected it can be given for quite a long time. I had to give it  as subcutaneous injections for I think 6 weeks once for an abscess. Is your bun getting shots or oral penicillin? If oral… then you should find a new vet!

I’ve used Benebac probiotic in the past, but now I know there are several rabbit-specific ones out there that I’ve seen online.

Rabbits can die if they get the wrong antibiotics or a massiv overdose. There are many types of rabbit-safe antibiotics though, and penicillin is rabbit safe if given by injections. Here is Medirabbit’s list of rabbit safe antibiotics: Safe Antibiotics (medirabbit.com)

Rabbit specific probiotics often contain certain strains of saccaromyces cerevisiae. The healthy rabbit gut also contains the bacterium enterococchus faecium, which is a common ingredient in animal probiotics. So look for either of those two, or both, when you look for rabbit probiotics. Lactic acid bacteria (which are very common in probiotics for humans and dogs) are believed to be less useful for rabbits. They wont harm, but they might get killed off already in the stomach by the strong stomach acid, in which case they (obviously) will have no function at all.

Penicillin when injected is safe, given the proper dosage of course. If you have any hesitancy around the competency of your vet, then you can actively search for another and discuss the treatment plan prescribed (but continue the current, as others have said).

Penicillin for two weeks on its own is not “harmful” — I’ve done 21 days of PenG injections for one of my rabbits for syphilis.