Adverse Drug Reactions

One in four people who walk out of the doctor's office with a prescription may be headed for trouble from an adverse drug event. And a new study suggests that a more than a third of those unwanted and potentially dangerous side effects could have been prevented with better prescribing practices and doctor-patient communication.

Although several studies have looked at the issue of adverse drug events among hospital patients, researchers say little is known about how frequently these complications occur among outpatients who take prescription drugs at home.

The study, published in the April 17 issue of The New England Journal of Medicine, examined adverse drug events reported among 661 patients who received at least one prescription drug from four primary care clinics in the Boston area.

Researchers found that 162 of these patients (25%) reported an adverse drug event for a total of 181 adverse drug events. Thirteen percent of the adverse drug events were serious, and 11% were considered preventable. Serious reactions in this study included drops in heart rate, drops in blood pressure, or bleeding from the stomach or intestines.

But the study found that the severity and duration of many of the adverse drug events reported would have been substantially reduced if different actions had been taken. Researchers say these ameliorable events occurred when doctors failed to respond to drug-related symptoms and when patients failed to inform doctors about these symptoms.

"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. "Clearly, strategies to improve doctor-patient communication are essential to the outpatient setting."

Of the 20 adverse drug events that were preventable, nine were due to the selection of an inappropriate prescription drug, two to the wrong dose, and two to the wrong frequency of use.

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

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.

Of those who reported an adverse drug event, 16% said their symptoms required medical attention, such as a visit to an urgent care clinic or emergency room.

Researchers found the only factor that increased the risk of adverse drug 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.

But in an editorial that accompanies the study, William M. Tierney, MD, of the Indiana University School of Medicine, writes that the errors of omission may be just as dangerous as the errors of commission.

Teirney says most studies on medication errors and adverse drug events have focused on the effects of mixing too many drugs. But other studies have shown that many patients are not getting the drugs they need despite the proven benefits.

For example, research shows that many heart attack victims are not prescribed beta-blockers or aspirin despite repeated studies that show these drugs substantially reduce the risk of death among these patients.

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