Since goats are not an animal with major agricultural focus in the US, drug companies often do not test their drugs on goats.  Many appropriate medications are therefore, “off label”  or “extra label”.  Since goats have a very efficient metabolism, the amount and duration of treatment is not easy to predict without testing. Here is a site that appears to be “well-vetted” (pun intended) that may be useful. It includes not only common drugs and dosages, but also milk and meat withdrawal times to be sure the medication is out of the animals’ system.
See Drug and Dosage Information Here >