Yucky medicine you gave him, hahhahahha !
Hopefully hes feeling a bit more fiesty! Just keep observing him.
Sounds to me, you definitely have yourself a wc collared.
Just be patience, keep trying to handle, little at a time.
Is he attempting to eat yet?
WC's are alot harder to care for, until hes acclimated.
He should be more healthy, now that he had the panacur, and got rid of the worms. So thats one step in the right direction.
Now you have to keep feeding him (if hes not eating by himself) for awhile till he does !
I know you are probably thinking well how, IF HES ATTACKING ME? 
Well, VERY CAREFULLY, hehhehehhee ! You have to be tougher than him, 
I just grabbed my wc's anyway, don't try to get him from OVERHEAD, thats how their enemies attack them, so its normal for the collared to want to defend himself !
Have your hand go into his body from the side, or even low down, in the front of his face, allowing him to see your hand .
Just keep trying ! 
Eve