hello my boy, Mischief had to be treated for pinworms just a couple of months ago and he was prescribed panacur, from what i have learned you do need to give them a probiotic, as its extremely harsh on their little systems, try avipro plus, nutribac or benebac, those are the ones i can remember of the top of my head, theres another but i cannot remember it right now, also give him some nice tepid baths like a temperature for babies, and that will help them pass stools still, because if yours does have trouble like mine did that will help it, it took Mischief about a month to get his system back to normal, and they can get a bit grouchy too on the meds, at the moment my female, Venus is now having to be treated for worm eggs, so shes on panacur now and ive been giving her avipro plus and loads more water (spraying her and
bathing her) right from the start of the treatment and shes already shes coping a lot better than what Mischief did, so hopefully it wont affect her as badly, i didnt start probiotics and
bathing with Mischief till late in his treatment. also if he isnt eating well try making him a slurry, im not sure what that entails as i havent had to do it but others here know loads about it so hopefully someone else will come along and help you out some ore.
hope this helps and your little one feels better soon.
Anny, Venus and Mischief