My friend has a rather large dog that has dysplasia anyone know if he can obtain Nembutal to help out?

He cannot legally obtain this.

 

I take it you mean he wants to euthanize the dog? If so and provided all other measures have been exhausted, it is possible to have a vet do that but sometimes need to try a number of vets. They will not do it on demand, only if in their opinion the animal is suffering and there is nothing else that can be done to alleviate it.