Viagra was developed as a heart medication. The idea was that it would widen arteries and avoid heart attacks.

During trials conducted by Pfizer it was shown not to aid the heart but, to the company's surprise, those taking it reported having the benefit for which the medication became famous.

If, now, it has an additional benefit (the avoidance of jet lag) there is absolutely nothing wrong in taking it for that purpose -- assuming, of course, that your doctor prescribes it.

What I am concerned about is a possible side effect -- inhibiting sleep. Hence, I raised the question in this thread.