Pharmaceutical Research

Possible problematic drug interactions are not always reported in medical records

Doctors know that prescribing certain drug pairs can have dangerous side effects. For example, combining warfarin, a blood thinner, with an anti-inflammatory drug can increase the risk of gastrointestinal bleeding. A recent survey of medical records found that when doctors coprescribe certain drugs, they typically don't document what they told their patients about possible drug interactions; however, they do order more laboratory tests to monitor patients.

Jennifer Elston Lafata, Ph.D., of the Henry Ford Health System, and fellow researchers used pharmacy claims data from 10 organizations comprising the HMO Research Network's Centers for Education and Research on Therapeutics (CERTs) to identify those patients who received a potentially dangerous drug pair between January 1 and December 31, 2000. In addition to a warfarin and anti-inflammatory combination, they looked for a heart medication (digoxin) given with calcium channel blockers (verapamil or diltiazem) that can cause irregular heart rhythms and a blood cholesterol-regulating medicine (lovastatin or simvastatin) with calcium channel blockers (verapamil or diltiazem) that can cause muscle weakness.

When they collected data from medical records for these patients, the researchers found that between 16 and 37 percent of patients had no medical record documentation of the coprescribing of those drug pairs, calling into question whether a clinician was aware the patient was using both medications. Regarding steps to mitigate potentially dangerous interactions, only 1 to 14 percent of patients had any documentation in the medical record of the risks associated with the use of both drugs, and 3 to 14 percent had any documentation that patient education was provided at the visit. This inadequate recordkeeping could pose a legal liability for the clinician.

More commonly, documentation of changes in clinical management was observed in the majority of patients (64 to 79 percent) prescribed the drug pairs, usually through laboratory testing. Lack of documentation regarding associated risks or failure to make a clinical change may not necessarily reflect a deficit in physician knowledge of the risks. Such omissions, however, call into question the adequacy of documentation and have obvious medico-legal implications. Medical record documentation can go a long way to illustrate that a patient was informed and accepted the alternative risks, as well as the potential benefits associated with combination therapy.

This study was funded in part by the Agency for Healthcare Research and Quality (HS11843).

See "What do medical records tell us about potentially harmful co-prescribing?," by Dr. Lafata, Janine Simpkins, M.A., Scott Kaatz, D.O., and others in the July 2007 The Joint Commission Journal on Quality and Patient Safety 33(7), pp. 395-400.

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