Jessica's doctor wanted to prescribe a sulfa drug in a cream for her to put on her skin. She reminded him that she was severely allergic to sulfa.

He said, "Oh, it won't hurt you; it's just going on your skin."

She said, "I don't want any drug with sulfa in it."

Eventually, he agreed to write a prescription for a drug without sulfa. When Jessica got to the drugstore, she double-checked with the pharmacist. He assured her that the cream did not have any sulfa in it.

Jessica rubbed it into her skin and went to her job in a delicatessen. She started cutting meat. On a downward stroke of the meat cleaver, she passed out, chopped off all the fingernails on one hand, and collapsed in a heap on the floor.

It turns out that the doctor had decided to get around her refusal to take sulfa by pretending to change the prescription. He even called the pharmacist and told him to tell Jessica that the drug didn't have any sulfa in it if she asked. Jessica passed out as a result of being given a drug to which she had a known allergy.

The doctor in the emergency room said, "If you are exposed to sulfa just one more time, you will die." Today, Jessica wears a medic alert bracelet.

Research confirms that doctors often downplay the risks of side effects. For example, doctors at the Mayo Clinic did a study of people who were prescribed new drugs to take when they went home from the hospital. Only 11 percent said that they had been warned about possible side effects.

Once patients have started taking a drug, that picture doesn't change much. Researchers at the University of California at San Diego found that doctors routinely brush off patients' complaints of side effects. Perhaps that's one reason why up to 19 million people land in the emergency room each year, as Jessica did, as a result of problems with the medicines they take.

Side effects of medicines result in more than 300,000 deaths each year in the U.S. This number includes 106,000 patients in hospitals, according to research reported in the Journal of the American Medical Association.

Among patients who aren't hospitalized, side effects of drugs kill about 218,000 people each year and cause other serious problems as well. About 3 million people are admitted to long-term care facilities each year because of side effects of medicines, according to research published in the journal of the American Pharmaceutical Association.

Market research firm IMS says that nearly 4 billion prescriptions are filled every year in the U.S., excluding those used in hospitals. That's roughly 13 prescriptions for every man, woman and child in the country. Drugs can be life-saving. But using so many drugs makes it likely that problems will arise. Many people don't benefit from treatments - and many are harmed.

For example, according to a website run by doctors called www.thennt.com, antibiotics for sinus infections provide no benefit for 93 people out of 100. They help resolve symptoms faster for about 7 patients out of 100. They also harm about 13 patients out of 100 due to side effects.

Weight gain is a common side effect of many drugs. For example, a federal government report noted that 30 percent of patients taking the drug Zyprexa gained at least 7 percent of their baseline weight (14 pounds for someone who weighs 200 pounds). The story is similar for many other medicines: While they help some people, they also often cause harm.

You can reduce the chances that you will experience serious problems by asking thoughtful questions when your doctor prescribes a drug for you. This step is especially useful if you are expected to take the drug for a long time. Your questions might include:

• What is this drug intended to do?  
• How will we know if it's working for me?
• When will we know if it's working for me?
• What big problems should I be watching for, and what do I do if they occur?

By asking questions like these, you can work with your doctor to figure out if the drug's benefits outweigh its risks for you.