Adherence to black box warnings for prescription medications in outpatients.
BACKGROUND
Few data are available regarding the prevalence of potentially dangerous drug-drug, drug-laboratory, and drug-disease interactions among outpatients. Our objectives were to determine how frequently clinicians prescribe drugs in violation of black box warnings for these issues and to determine how frequently such prescribing results in harm.


METHODS
In an observational study of 51 outpatient practices using an electronic health record, we measured the frequency with which patients received prescriptions in violation of black box warnings for drug-drug, drug-laboratory, and/or drug-disease interactions. We performed medical record reviews in a sample of patients to detect adverse drug events. Multivariate analysis was conducted to assess the relationship of prescribing in violation of black box warnings to patient and clinician characteristics, adjusting for potential confounders and clustering.


RESULTS
Of 324 548 outpatients who received a medication in 2002, 2354 (0.7%) received a prescription in violation of a black box warning. After adjustment, receipt of medication in violation of a black box warning was more likely when patients were 75 years or older or female. The number of medications taken, the number of medical problems, and the site of care were also associated with violations. Less than 1% of patients who received a drug in violation of a black box warning had an adverse drug event as a result.


CONCLUSIONS
About 7 in 1000 outpatients received a prescription violating a black box warning. Few incidents resulted in detectable harm.
Lasser
Karen E
KE
Department of Medicine, Cambridge Health Alliance and Harvard Medical School, Cambridge, Mass, USA. klasser@challiance.org
Seger
Diane L
DL
Yu
D Tony
DT
Karson
Andrew S
AS
Fiskio
Julie M
JM
Seger
Andrew C
AC
Shah
Nidhi R
NR
Gandhi
Tejal K
TK
Rothschild
Jeffrey M
JM
Bates
David W
DW
D000293:Adolescent; D000328:Adult; D016907:Adverse Drug Reaction Reporting Systems; D000367:Age Factors; D000368:Aged; D000553:Ambulatory Care; D001900:Boston; D004348:Drug Labeling; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D064420:Drug-Related Side Effects and Adverse Reactions; D005260:Female; D006801:Humans; D008297:Male; D016347:Medical Records Systems, Computerized; D008875:Middle Aged; D015999:Multivariate Analysis; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D012737:Sex Factors