Hi Sarah,
You would want to use the Duplocillin. Look at the concentration of the drug. You want the concentration to be 150K units of procaine and 150K units of benzathine per mL for a total drug concentration of 300K units per mL (I think the Duplocillin is a bit lower in benzathine but it isclose...but I would prefer finding the 300K unit per mL version). I think the Tripen only contains 62.5K units of each drug per mL. While either would work, you would have to dose more of the lower concentration drug. I trust that since you have researched this that you know that penicillin is safe only when used as an injectable. It also helps to buffer the meds with something like Lactated Ringers Solution since it really stings going in. And repeated injections in the same area can lead to some skin issues. Make very sure you are using the correct dosing both in frequency and amounts. This drug can cause problems if overdosed. And has a culture been performed to confirm pasteurella or is the treatment based solely on presentation? We have seen some interesting and unusual pathogens in rabbit infections over the past year. While at one time we generally assumed pasteurella...that is no longer true.
There are better alternatives to this drug if you are using a vet. I routinely use either Zithromax or Chloramphenicol against pasteurella with very good results.
Randy
