Getting an old dog to take bitter pills

I have never had trouble getting dogs to take pills. I just used a pincer-grip on either side of the jaw hinge to force them to stop clenching their teeth, shoved the pill as far back as I could reach, clamped the jaw shut as if I were taming an alligator, and soothingly massaged the throat, blew in the nose, whatever it took and however many minutes it took to get a good swallow. Yes, some dogs I still had to follow around for a while to make sure they didn't spit it out, but schnauzers are tricky.
But, old dog. In his sixteenth year. Sore from arthritis, and sore back teeth; on synthetic opiates for pain. He is too old to have anaesthetic for dental care. It hurts him if I pry open his mouth. It hurts if he struggles. Too old to be physically restrained. And still stubborn as blazes. What to do?
His synthetic opiates are in a capsule, but very bitter if a tooth should pierce the capsule. He gets four of these a day. His metronidazole for irritable bowel is also extremely bitter, he gets one and a half tablets twice a day with meals.

HERE IS WHAT WORKS FOR THIS OLD DOG: 

My invention. I call it PeaChee Whiz, and have been thinking of writing Irene Rosenberg at Kraft Foods to tell her about it.
Many websites recommend peanut butter, but my dog licks and licks it on the roof of his mouth until he uncovers the bitter pill. Too soft. And some websites recommend cheese. But my old dog is small, and any piece of cheese large enough to hide a pill he wants to chew. Bad. Chewing bad. Tastes bitter.
So I tried Cheese Whiz (yes, trademarked, Kraft Foods etcetera etcetera). I know, plastic cheese, poison in a bottle, all that. To tell you the truth, now that it is in my refrigerator for the first time since the '60s, I like it too, in moderation. Gee, it's salty. But tasty on a burger or celery sticks. The Cheese Whiz was not successful either, it was too soft to really hide anything. Then I got an idea. I mixed 2/3 peanut butter and 1/3 Cheez Whiz. And refrigerated the result. It is perfect. The dog loves it, he swallows a big glob of it whole, never tries to chew it, and doesn't need forcing to take his pills. It's amazing. PeaChee Whiz. Try it and see if it works for your old dog.
Thanks for reading
NorthStar