One in four people who walk out of a doctor's office with a prescription may be in for trouble from an adverse drug reaction. And more than a third of those with unwanted and potentially dangerous side effects could have been prevented with better doctor-to-patient communication and better prescribing practices, according to a new study published in the April 17 issue of The New England Journal of Medicine. Previous studies have looked at the issue of adverse drug events among hospital patients, but researchers say that little is known about how frequently complications occur among outpatients who take the medications at home.

Researchers examined adverse drug events in 661 patients who received at least one prescription drug from four primary care clinics in the Boston area. They found that 162 of these patients (25%) reported an adverse drug event for a total of 181 adverse drug events. 13% of the events were serious, and 11% were considered preventable. Serious reactions in the study included drops in heart rate, drops in blood pressure, and bleeding from the intestines or stomach. Of those who reported an adverse event, 16% said their symptoms required medical attention, like a visit to an urgent care clinic or emergency room.

They found that the severity an duration of many of the adverse drug events reported could have been substantially reduced if different actions had been taken, like if some of the doctors had responded to the patient's descriptions of the drug-related symptoms, and if some of the patients informed their doctors of the symptoms instead of keeping quiet. Of the 20 adverse drug events that were preventable, nine were due to the selection of an innapropriate prescription drug, two to the wrong dose, and two to the wrong frequency of use.

"Patients often had symptoms for months without any changes in their medications, and only a small percentage of patients reported that symptoms led to a visit to a physician," writes researcher Tejal K. Gandhi, MD, MPH, of Brigham and Women's Hospital in Boston and colleagues.

The prescription drugs most frequently involved in adverse drug reactions were NSAID pain relievers, selective serontonin reuptake inhibitors (SSRIs) commonly used to treat depression, and heart disease medications such as beta-blockers and ACE inhibitors.

The most frequently reported preventable and treatable adverse drug events were those related to the central nervous system (such as sexual dysfunction), gastrointestinal disorders, and heart problems.

A person's age, sex, or other demographic characteristics did not affect the likelihood of suffering an adverse drug event, according to this study. The only factor that increased the risk of such events was the number of medications a person took - the number of adverse drug events per person increased by 10% for each additional prescription drug they took.

William M. Tierney, MD, of the Indiana University School of Medicine, wrote an editorial to be accompanied with this study in The New England Journal of Medicine. For his view on this topic, please read the next article in the SAA news section titled "An Evaluation of Adverse Drug Reactions."