Sorry to hear about your friend's situation; that must be terribly distressing to him, and to you, too.

You may not have received an answer because fewer people deal with tardive dyskinesia today than in the past, and few of us may have had personal experience with it. I do seem to recall doctors used to prescribe a med called Cogentin that was helpful; there may be newer, better treatments available now. I have not heard of any homeopathic remedies, sorry.

Has your friend called his pdoc about this?