As the others said, tis an antipsychotic.. it's related to chlorpromazine, which is used more commonly in humans.
Not only is it not recreational, but occasionally antipsychotics can have a severe reaction in people called
acute dystonia, basically a really painful and intense spasm of the neck, face and eye muscles, needing urgent medical treatment - so not something anyone should randomly be trying! There are also a lot of unpleasant long term side effects that can be associated with antipsychotics but this isn't so relevant if you are just going to try a pill as a one off, haha.
I feel very strongly that antipsychotics shouldn't be messed about unless under medical supervision, they are pretty heavy duty drugs. And they won't get you high either, most you can expect is to feel knocked out and uncoordinated - def not worth it
Hope your dog recovers soon, I presume this has been given as a sedative?