One of the most widely prescribed prescription drugs, gabapentin, is being taken by millions of patients despite little or no evidence that it can relieve their pain.

In 2006, I wrote about gabapentin after discovering accidentally that it could counter hot flashes.

The drug was initially approved 25 years ago to treat seizure disorders, but it is now commonly prescribed off-label to treat all kinds of pain, acute and chronic, in addition to hot flashes, chronic cough and a host of other medical problems.

The F.D.A. approves a drug for specific uses and doses if the company demonstrates it is safe and effective for its intended uses, and its benefits outweigh any potential risks. Off-label means that a medical provider can legally prescribe any drug that has been approved by the Food and Drug Administration for any condition, not just the ones for which it was approved. This can leave patients at the mercy of what their doctors think is helpful.

Thus, it can become a patient’s job to try to determine whether a medication prescribed off-label is both safe and effective for their particular condition. This is no easy task even for well-educated doctors, let alone for desperate patients in pain.