Its difficult to work out for goats!
Under "the cascade" we can prescribe anything as nothing licensed for goats, however we have to be careful as the time it takes drugs to be broken down enough in milk or meat to not be harmful have not been established in goats. As such, our best options are to use drugs allowed in milking cattle, and apply that withdrawal period.
Recently, the major fluke treatment triclabendazole (one of the ingredients in combined among other brand names) has been re-classified, such that most formulations should not be used in any animal that at any time will produce milk for human consumption, with the exception of Fasinex 240, licensed for use in dry dairy cattle with a 50 day milk withdrawal, ie use in dry period and don't drink milk til 48hr post kidding.
hope that may help
Suzanne