Adverse drug events in ambulatory care.
BACKGROUND
Adverse events related to drugs occur frequently among inpatients, and many of these events are preventable. However, few data are available on adverse drug events among outpatients. We conducted a study to determine the rates, types, severity, and preventability of such events among outpatients and to identify preventive strategies.


METHODS
We performed a prospective cohort study, including a survey of patients and a chart review, at four adult primary care practices in Boston (two hospital-based and two community-based), involving a total of 1202 outpatients who received at least one prescription during a four-week period. Prescriptions were computerized at two of the practices and handwritten at the other two.


RESULTS
Of the 661 patients who responded to the survey (response rate, 55 percent), 162 had adverse drug events (25 percent; 95 percent confidence interval, 20 to 29 percent), with a total of 181 events (27 per 100 patients). Twenty-four of the events (13 percent) were serious, 51 (28 percent) were ameliorable, and 20 (11 percent) were preventable. Of the 51 ameliorable events, 32 (63 percent) were attributed to the physician's failure to respond to medication-related symptoms and 19 (37 percent) to the patient's failure to inform the physician of the symptoms. The medication classes most frequently involved in adverse drug events were selective serotonin-reuptake inhibitors (10 percent), beta-blockers (9 percent), angiotensin-converting-enzyme inhibitors (8 percent), and nonsteroidal antiinflammatory agents (8 percent). On multivariate analysis, only the number of medications taken was significantly associated with adverse events.


CONCLUSIONS
Adverse events related to drugs are common in primary care, and many are preventable or ameliorable. Monitoring for and acting on symptoms are important. Improving communication between outpatients and providers may help prevent adverse events related to drugs.
Gandhi
Tejal K
TK
Division of General Internal Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA. tgandhi@partners.org
Weingart
Saul N
SN
Borus
Joshua
J
Seger
Andrew C
AC
Peterson
Josh
J
Burdick
Elisabeth
E
Seger
Diane L
DL
Shu
Kirstin
K
Federico
Frank
F
Leape
Lucian L
LL
Bates
David W
DW
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000553:Ambulatory Care / Q000706:statistics & numerical data*; D001900:Boston; D003625:Data Collection; D064420:Drug-Related Side Effects and Adverse Reactions; D005260:Female; D006801:Humans; D007049:Iatrogenic Disease / Q000517:prevention & control; D008297:Male; D008508:Medication Errors / Q000706:statistics & numerical data*; D008875:Middle Aged; D011320:Primary Health Care; D011446:Prospective Studies