The vicissitudes of Vioxx point to some truths that some doctors knew but many patients did not. The pain-relieving prescription drug was widely used until a test showed that in rare cases it could cause heart attacks or strokes. Something like panic set in. Merck took it off the market but now is considering offering it again but with additional warnings.

The Food and Drug Administration recently approved putting the drug back on the market under certain conditions that included a “black box warning” -the FDA’s most severe and reason for consumers to hesitate.

All drugs carry risks, notably possible side effects. What the Vioxx story demonstrates is the extent to which consumers are on their own to make risk judgments about pharmaceuticals. This occurs for reasons in part explained on today’s op-ed page by Dr. Erik Steele.

There are two ways to measure risk, “relative” and “absolute.” The Vioxx test showed a relative risk of a doubled chance of a cardiovascular event in prolonged use of the drug vs. a sugar pill. The absolute risk is 1.48 chances out of 100 for a person using Vioxx, as against 0.75 chances out of 100 for one using the sugar pill. That might be considered only a minor increase in risk, like the chance of a fatal accident in driving to New York including the big-city traffic hazards. Statistically, taking a plane would probably be safer. (The comparison is with staying home, which, of course, has its own risks like slipping and falling in the bathtub or tumbling downstairs.)

In addition to the risks, there are benefits to be considered. Vioxx or one of the other pain relievers may provide welcome relief from, say, an arthritic back or shoulder.

Then comes the question of balancing the risks against the benefits. A doctor, often in consultation with the patient, can try to decide whether a relatively minor risk is worth the relief from excruciating pain. The calculation will take into account other factors, such as the patient’s history of any heart problems. It’s like the almost subconscious calculation when we decide whether to risk a long trip, checking the weather report for possibilities of snow or freezing rain.

Figuring the risk vs. the benefit of taking a particular drug would be much simpler if it weren’t for advertising and promotion by the pharmaceutical industry. Patients are constantly being urged to demand particular drugs. The ads often soften the approach, in the course of a glowing description of the produce, with the helpful suggestion, “Ask your doctor.”

The drug companies also persuade doctors directly, showering them with test results, giving them free samples, and sometimes paying them fees for delivering lectures or for consultations or sometimes just wining and dining them.

So there is the story on how to think about Vioxx and its cousins, Celebrex and Bextra, as well as long-known over-the-counter remedies like aspirin and Ibuprofen. If it concerns you that consumers and their harried doctors are left to make guesses about drug safety, remember that the FDA has issued its warning. Now it’s just up to you to balance the risks, while factoring in special circumstances and ignoring outside pressure.