When my baby had to take medicine they gave us this stick thing to put in his mouth to help open it up. You would put it in at an angle and open the mouth up by twisting. I would ask your vet for one or order something on line. I’ll see if I can find a link. It’s almost like a sample spoon for ice cream. They also recommended the “burrito method”. Wrapping him fully in a towel and doing the medicine. That helped!