Antiparasitics are not toxic, and for the most part, basically all of them are extremely safe to use, even in extreme doses.antiparasitic drugs are regulated because they are extremely toxic, they are basically poisons... they are simply used at a dosage that's tolerated by the host but deadly to parasites.
sometimes u can find some lower dosages formulation sold otc, but will need a prescription for the higher dosage ones. kind of like dumb, because no one prevents a guy from taking 10 tablets at once, but well that's the law.
if u explain to ur doctor why u need them he will most certainly give u a prescription.
my doc also prescibes me the dewormer i use on my dog (cheaper than buying the vet equivalent).