DESIGN: Retrospective chart reviews and patient surveys.

SETTING: Eleven Boston-area ambulatory clinics.

PATIENTS: We randomly selected 2,248 outpatients, 20 to 75 years old.

MEASUREMENTS AND MAIN RESULTS: Among 2,248 patients reporting prescription drug use, 394 (18%) reported a drug complication. In contrast, chart review revealed an adverse drug event in only 64 patients (3%). In univariate analyses, significant correlates of patient-reported drug complications were number of medical problems, number of medications, renal disease, failure to explain side effects before treatment, lower medication compliance, and primary language other than English or Spanish. In multivariate analysis, independent correlates were number of medical problems (odds ratio [OR] 1.17; 95% confidence interval [95% CI] 1.05 to 1.30), failure to explain side effects (OR 1.65; 95% CI, 1.16 to 2.35), and primary language other than English or Spanish (OR 1.40; 95% CI, 1.01 to 1.95). Patient satisfaction was lower among patients who reported drug complications (P < .0001). In addition, 48% of those reporting drug complications sought medical attention and 49% experienced worry or discomfort. On chart review, 3 (5%) of the patients with an adverse drug event required hospitalization and 8 (13%) had a documented previous reaction to the causative drug.

CONCLUSIONS: Drug complications in the ambulatory setting were common, although most were not documented in the medical record. These complications increased use of the medical system and correlated with dissatisfaction with care. Our results indicate a need for better communication about potential side effects of medications, especially for patients with multiple medical problems.