Maybe I'm a little late on this but we've been having the same problem with Angus who is also 12 (going on 13). We took him to the vets on the 26th of May and he was prescribed Phenylpropanolamine 50 mg 2x's/day after they checked to make sure he didn't have any infection.
Well I thought it was working, hadn't seen any dribbles the last couple of weeks but yesterday he went downhill. He had a couple of pretty big wet spots on the linelonium (sp?) and quite a few dribbles. So today I went to the fabric store and I'm going to make him a belly band. The ones I've seen are for up to 75 lbs and needless to say he's a little over that
I almost feel like he's going to think it's degrading, but he's pretty good about stuff like that plus he'll only have to wear it when he's in the house.
Please keep us upd on how he's doing
Anna