S.H.
Well if you must begin your medications, and you cannot wait, then wean him.
Afterall, he is only "nursing" once a day... so that is pretty much almost there.
Just try and distract him. For me, when my daughter was almost at the end of weaning... I would just make myself "busy" and would stand up when she tugged at me.. and then kept myself "busy" and then told her "not now.." or something like that. Then, the child gets distracted and focused on something else. My daughter and my son was self-weaned. Each child is different...
Is it really your son who is wanting to nurse upon waking... or you who initiates it? If he does not ask...then don't do it. And he will probably be fine. Go according to his lead in this case. ie: If he doesn't ask, then don't offer.
And, he doesn't even nurse very long at this point, anyway. So, he's probably able to stop. It's just a "habit" he does upon waking...
so maybe, do something else upon waking... get up, and do another activity. Or just cuddle.
You are almost there... one time a day is hardly anything. But, yes, weaning is bittersweet for the Mom. I understand and went through that with both my children.
all the best,
Susan