Actually, I think the dose was the problem. He'd only been on it a couple of days and he told me later that he had tried beer to see what would happen. That was last Saturday and I wasn't home at the time, but when I came home his face was flush which he claimed was probably from a NA beer had drank. The next day he started talking about maybe taking two pills as his prescription was 250 mg, and I resisted. So, he decided to drink more on Monday - that still didn't do it, but he took 500 mg on Tuesday - and drank that afternoon - and that's when I nailed him with the breathalyzer. He did get sick, but it took longer. He said he felt bad immediately with a headache and his face got real hot, but it wasn't until several hours later that he started throwing up. On Wednesday he reacted to his aftershave (a mild reaction - his face got flush - but a reaction nonetheless).
We had read somewhere that typically you start with 500 mg for the first 1-2 weeks and then go to 250 mg for maintenance. He started on 250 and it had only been a couple of days, so I suppose it hadn't had time to build up in his system. He's been taking 500 mg on his own since then, and no I haven't been inspecting him or watching him take it.
He said that he wanted to see what would happen. He could be lying, but he kept insisting he needed to take 500 mg. He also said he got no high or pleasurable feeling from it - which may be from the Naltroxene. In a way, I guess I always knew he'd test it eventually - and now that he has, we'll see what happens from there.
For now, though, I'm taking the advice of those on this board. If he truly wants to quit, he will but I'm not going to stand over his shoulder and make him take the medicine. He's been good the last couple of days, and is at his doctor's this morning.
Thanks for everyone's comments.