Many people think that because a bird is smaller that it gets less medication per pound, but in many cases it's not true. Safeguard de-wormer is a good example of that... birds, cats and dogs get 10x what cattle and goats get. Do what you feel is best, or maybe call a vet school and ask them...
That's for cattle, not poultry.
Penicillin G
Here is some info:
http://avianmedicine.net/content/uploads/2013/03/18.pdf
Picture below is from this site: http://smartools.pharmdev.org/iu.html
-Kathy
With the penicillin you have, the dose for chickens and turkeys is about 0.15ml per *pound*. Haven't found any duck specific dosing, but I bet it's the same.
-Kathy