Calculating Medicine Dosages
Why doesn't my medication bottle say IU instead of 5mL like for children's medicine?
There's a couple of reasons for this - 1) most medicines are not tested/approved for use in rabbits specifically, so they won't have rabbit specific dosage (it's simply not cost effective to go through the approval process for rabbits). 2) Livestock medications come in different strengths or concentrations.
When you read your medication bottle, you'll see something about it's concentration. That's why we use IU in a lot of dosage calculations because medicines can be different strengths. We'll be using a bottle of Penicillin G Procaine for our example. It says on it 300,000 IU per mL. That means that for every 1 mL you take, you're getting 300,000 IU. A bottle of a different brand may say 100,000 IU per mL or something completely different.
Common rabbit dosages for various medications are available online. Simply google "Rabbit dosage Penicillin G Procaine", and you'll get several good links in the top 5 search results. We like Medirabbit and Wabbitwiki. Both give reliable, comprehensive lists of rabbit medications, as does the Merck Veterinary Manual. Generally they agree that it's 40,000 IU/kg to 60,000 IU/kg every 1-2 days. They abbreviate this differently.
sid = once a day
bid = twice a day
q = every h = hours q12h = every 12 hours
SC or SQ = Subcutaneous = under the skin
IM = Intramuscular = into the muscle
PO = Orally = ate or drank
The rabbit's weight today is 8.54 lbs or 3.87 kg. When we write the formula below, we insert the weight in kilograms. You know you've got the formula right when the units on top cancel out the units on the bottom and the remaining unit is the one you're looking for. For example, the IUs cancel out with the pink lines. The kilograms cancel out with the green lines, and the only unit leftover is mL, so I know that I have successfully converted the concentration and dose to the mLs I need to administer. The ending amount 0.52 mL is specific to this single rabbit. To customize it for your rabbit, simply enter your rabbit's weight instead of 3.87 kg (above where it says rabbit weight).
This concentration x dose x rabbit weight formula works for any medication, not just Pen G. Simply read the bottle to get the concentration and insert it. Look up the rabbit dosage and insert that, and then add your rabbit weight.