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Physician compliance with medication black box warnings is mixed

Over 40 percent of outpatients received at least one medication with a Food and Drug Administration black box warning (BBW) that applied to them during a 30-month period, according to a new study supported by the Agency for Healthcare Research and Quality (HS11843). Physicians varied in their compliance with these warnings, which can range from prohibiting use of a medication by pregnant women to contraindications for use with another medication.

Researchers determined the frequency of use of BBW medications in outpatient care using data from 10 U.S. health plans that form the HMO Research Network's Center for Education and Research on Therapeutics. They evaluated prescribing compliance for 19 drugs or drug groups with 4 types of BBWs: requiring laboratory monitoring before a patient starts a medication; monitoring during continued therapy (such as liver enzyme testing for isoniazid); listing contraindicated co-medications; and mentioning contraindicated prescribing during pregnancy.

Few instances were found of absolutely contraindicated BBW drugs prescribed in pregnant women. Also, there was almost no co-prescribing of contraindicated drugs with the BBW drugs that prolong the heart's QT-interval, which can lead to dangerous arrhythmia. However, 9 percent of the four drugs with warnings about contraindicated co-medications were prescribed on the same day as a contraindicated drug. Finally, for nearly half of the 74,666 newly dispensed and 13 percent of 51,560 continued dispensed BBW medications, patients did not get the recommended laboratory test for baseline or routine monitoring, respectively.

See "FDA drug prescribing warnings: Is the black box half empty or half full?" by Anita K. Wagner, Pharm.D., M.P.H., D.P.H., K. Arnold Chan, M.D., Sc.D., Inna Dashevsky, M.Sc., and others, in the November 2005 Pharmacoepidemiology and Drug Safety.

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