Amprolium, the typical medication in US medicated feed, is a Thiamine antagonist. Blocks uptake. Its effects can be easily overcome by ensuring a thiamine rich environment. Legumes (i.e., peas, soy) and seeds, like the ever popular BOSS, are both good thiamine sources. You can suppliment and effectively "cancel out" the Amprolium - though the larger the critter, the less brief amprolium intake will affect them. Yogurt (fortified) is a source too, but only 1/3 to 1/5th as good as peans, beens, or sunflower..
and yes, I know the pea in a pod is technically the legume, the pea seed inside technically a pulse. Lets not get pedantic.