According to Charles Dickens in "A Tale of Two Cities," the period of the French Revolution was both the best of times and the worst of times. I won't disagree with him in general, but if we restrict ourselves to medical matters, a case can be made for here and now as a better choice. We live in the best of times, compared with all of history, but the worst of times compared with the relatively near future.

A look backward even a couple of hundred years provides a dismal picture. Vaccination against smallpox using cowpox serum was introduced into the western world only with Edward Jenner's work in the 1790s (although inoculation with live smallpox had been practiced in eastern Europe and Asia for centuries). Before that, you either died or recovered naturally from infectious disease, while the medical profession stood by helpless.

Perhaps people were just as happy to manage without doctors. In the absence of safe ways of rendering a patient unconscious, surgery of any form was torture. It wasn't until the 1840s that ether, nitrous oxide, and chloroform were introduced as general anesthetics, with cocaine as a local anesthetic not employed until 50 years later. Our ancestors usually lost their teeth by middle age, and if you imagine having a root canal while fully conscious and without painkillers you can easily see why. Samuel Pepys, keeping his famous diary in the 1660s, never failed to note each March 26 that it was the anniversary of his operation for the removal of a kidney stone. An operation without anesthetics could make a great impression.

For even the smaller ailments there was little relief. Today we have a dozen over-the-counter drugs to treat a headache or a sprain. Aspirin to handle pain and reduce inflammation was not introduced until 1893. An infusion made from willow bark provided a natural aspirin-like equivalent, but it was less strong, less reliable, and far less available. A century and a half ago pain, like disease, was something a king or a peasant lived with and died with.

As for the powerful drugs that we have come to regard as our natural right, not one was available a century ago. Syphilis was for hundreds of years the equivalent of today's AIDS, incurable and usually fatal. Salvarsan, the first safe and effective treatment for syphilis, was developed in 1909. Its discoverer, Paul Ehrlich, was the first to speak of a "magic bullet" which could kill bacteria.

And as new drugs came on the scene, they certainly must have seemed like magic. The sulfonamides, or sulfa drugs, were used after 1936 to perform wonders for pneumonia, meningitis, and a wide variety of urinary infections. Penicillin, discovered by Alexander Fleming in 1928 but not developed and widely used until the 1940s, saved unnumbered thousands of lives during and after the Second World War. On a personal note, after my father in 1945 suffered a burst appendix and peritonitis, penicillin saved his life and gave him another 27 years.

The discoveries continued through the whole century. Steroids, beginning with the use of cortisone in 1948, have provided relief for millions of sufferers from arthritis and other forms of chronic inflammation. Recently we have seen statins heralded as the latest miracle medication, helping patients with high cholesterol, heart problems, stroke, and, we now suspect, osteoporosis and Alzheimer's disease.

Given all this progress, with every promise of more to come, you may ask how I can possibly label this the worst of times as well as the best. Rather than give you one reason, I will give you a hundred. Pick up a prescription and read the warnings that go with it of possible side effects. The trouble with almost all the medications that we take is that they are pills or injections. They are systemic drugs, meaning that they affect the whole body. Some of the side effects are well known. For example, anti-inflammatory medications such as aspirin and ibuprofen have bad effects on the digestive tract. Cholesterol-reducing drugs can hurt liver and kidneys, which is why their use calls for frequent blood tests. But far more worrisome, at least to me, are all the side effects we have not so far discovered. When cortisone was first used to treat arthritis, it produced miraculous results. Only later did other effects on the body - weakening of bones, moon face, suppression of adrenal gland function, personality changes, and effects on secondary sexual characteristics - come to light.

The problem is, today's medications are not the "magic bullets" sought by Paul Ehrlich. They are not specific enough, and their actions tend to be far too global. It is as though we wanted to get rid of Saddam Hussein, and decided that the answer would be to drop a hydrogen bomb on Baghdad. It would certainly do the trick (I have the horrible feeling that some military extremists would think it a good idea), but it is the wrong answer. If a weed grows in your garden, applying weed-killer everywhere and looking to see what's left afterwards is not the preferred solution.

In some desperate cases, such an approach is all that today's medicine can offer. For example, chemotherapy for cancer usually consists of the injection of drugs known as anti-metabolites. These drugs kill cancer cells when the cells divide. They also kill normal body cells, at a somewhat slower rate. You are making a bet in this situation that the cancer cells will die and you will not. Many of the drugs that treat internal parasites make the same bet: parasite dies before patient.

All this will, I believe, change dramatically within the next 20 years. The knowledge we are gaining of the genome, and the way that particular cell functions are turned on and off by particular genes, is going to give us true "magic bullets" with which to fight disease. The first of these treatments, exquisitely tuned to minute differences between healthy and sick cells, are already being tested. In medicine, the best is yet to be.

And if these magic bullets can at last conquer every known disease, without side effects, what next? Well, we will still have to deal with the ways that we choose to kill ourselves. I said earlier that penicillin gave my father an extra 27 years of life, but I was probably being unfair to penicillin. My father died of heart disease and lung cancer - after 55 years of two packs a day of cigarettes.

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