It sure feels like the house of cards is crumbling. Hardly a week goes by without some pharmaceutical drug or other turning out to have unacceptable side effects. Yesterday it was hormone replacement therapy, today it is Vioxx, tomorrow it’ll be Viagra. You think I’m joking? There used to be a myth (maybe there still is) that certain sexual practices would make you go blind. Well, the use of Viagra might be added to that list very soon. It turns out that Viagra regulates a chemical that constricts the body's arteries and ophthalmologists are now identifying certain types of people who are susceptible to having the blood supply to the optic nerve cut off if they use it.