Meds or simply a physically taxing procedure?
@gerago:
I don't fly anymore but I've found that doctors rarely ask what kinds of activities you might be involved in before admistering drugs or performing minor surgeries. In my recent procedure, I would have no idea what the guy used to sedate me unless I had specifically asked. I also never really considered, nor was I informed, that I would be going for almost 3 days undernourished and dehydrated.
Additionally, almost any invasive medical procedure, even a dental filling, can be physically taxing to the point that the patient might not be aware of its effects on performance. Perhaps the focus shouldn't be so much on the drugs themselves, but on the trauma and stress of climbing Mt. Everest.