That the drug Viagra has the capacity to add life to flagging sex lives in not in doubt. Less clear is whether the pill and other lifestyle drugs that are bound to follow it - could have a rather less stimulating effect on Britain's National Health Service. The concern encapsulated by Viagra is that, if the ageing UK population begins to demand drugs not only to cure its illnesses but also to make it younger or happier, the NHS would quickly find its coffers empty.