Medication errors and patient safety

When physicians and health care administrators talk about about "improving patient safety," they're usually referring to preventable events that occur in hospitals: blood transfusion mismatches, or infections in intensive care units, to give examples. But the vast majority of health care takes place in communities, in outpatient or ambulatory care settings ("ambulatory" being something of a misnomer, since wheelchair-bound patients can and do seek treatment in offices). In this setting, errors in dosing prescription and over-the-counter medications are an important safety issue.

Taking doses that are too large, or taking correct doses too frequently, can cause serious and even fatal side effects. An advisory committee to the Food and Drug Administration recently voted to lower the maximum daily dose of Tylenol due to evidence that many adults sustain liver damage by inadvertently taking too much. On the other hand, inadequate dosing of medications can result in conditions such as epilepsy, diabetes, and high blood pressure being poorly controlled.

Patients may take medicines improperly because their doctor gives inadequate oral or written instructions. More prescription medications also may make errors more likely. In a 2006 study published in the Annals of Internal Medicine, Dr. Terry Davis and colleagues examined the relationship between literacy levels and a patient's understanding of common prescription drug labels.

In this study, 395 English-speaking adults were recruited from 3 primary care clinics' waiting rooms. They were shown 5 labeled prescription medicine bottles and asked to describe how they would take each medication, including the number of pills to be taken in a day. The interview concluded with a health literacy assessment to determine the patient's literacy level: low (sixth grade and lower), marginal (seventh to eighth grade), or adequate (ninth grade and higher).

Out of 1,975 responses, 374 were incorrect. Most incorrect responses were dosage errors (51.8 percent) and dose frequency errors (28.2 percent). A few patients were unable to find the instructions on the label (5.8 percent) or admitted to being unable to read (3.2 percent). Incorrect responses were strongly associated with low and marginal literacy levels, and the risk of an incorrect response increased with more medications used. Surprisingly, many patients who read the instructions correctly still counted out an incorrect number of pills.

This study reinforced my longstanding (but unfortunately time-consuming) practice of asking all of my patients who take regular medications to bring in their pill bottles at every visit so we can go over how to take each one properly. Quite often, I'd find that another doctor had added or changed a prescription without telling me about it, often leading the patient to take two different medicines for the same condition. Without a single physician coordinating care, medication errors become almost inevitable. So how might health reform address this problem? Stay tuned.