Did the doctor explain it to him? Dd is very defiant about medicine, but with an ear infection she actually listened to the dr who told her she had to have it and she could have a treat afterwards (I prompted that). Then she and I went shopping for the 'treat' which was jellybeans (yeah real special lol) and she could have one after each dose (which was three per day and more sugar than she had ever had I think!).

It sounds like the power needs to be given to him in some way. What if you sat down with him in the morning (when he's fresh and cooperative) and made a deal: look, you have to take it do let's talk about ways you are happy to do it. Do you want it on a spoon or in a cup, or with a treat etc. if he says no I would tell him you will swaddle him and force feed him because that's how important it is.

Unfortunately if the gentle approach fails, then I wouldn't hesitate from forcing it. Infections are terrible and can lead to other complications.