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Study: Drug Labels are Prescriptions for Mistakes

Lower literacy, multiple medications associated with medical misunderstanding

PHILADELPHIA, November 29, 2006 – A new study to assess understanding of five common prescription label instructions found that patients had difficulty comprehending how much and how often the medication should be taken. Misunderstanding was particularly high among those with lower literacy (eighth grade level or below) and those who took many prescription drugs.

The study, “To Err is Truly Human: Literacy and Misunderstanding of Prescription Drug Labels,” is scheduled for online release to the public by Annals of Internal Medicine on November 29, 2006, at www.annals.org. The article also will be printed in the December 19 issue of Annals of Internal Medicine.

The researchers interviewed 395 English-speaking adults in three states. The five medications identified for the study were two antibiotics (amoxicillin and trimethoprim); an expectorant (guaifenesin); an anti-hypertensive, channel blocking agent (felodipine); and a diuretic (furosemide). Patient literacy was classified either as low (sixth grade and below), marginal (seventh to eighth grade), or adequate (ninth grade and higher).

Study findings included:

  • Although 70.7 percent of patients with low literacy correctly stated the instructions “Take two tablets by mouth twice daily,” only 34.7 percent could demonstrate the number of pills to be taken daily.

  • The rates of understanding individual labels ranged from 67.1 percent for the instructions for trimethoprim (“Take one tablet by mouth twice daily for seven days”) to 91.1 percent for the instructions on the label for felodipine (“Take one tablet by mouth once each day”).

  • Patients with low literacy were less able to understand the meaning of all five medication labels than those with adequate literacy.

  • The majority (51.8 percent) of incorrect patient responses reflected an error in dosage (e.g., tablespoon vs. teaspoon), and 28.2 percent stated the wrong dose frequency (e.g., “One tablet each day for seven days” instead of “Take one tablet by mouth twice daily for seven days”).

  • Most patients did not pay attention to the auxiliary (warning) labels (e.g., “Do Not Take Dairy Products Within One Hour Of This Medication”) and those with low literacy were more likely to ignore them.

Health literacy expert and lead author Terry C. Davis, PhD, chairperson of the American College of Physicians Foundation’s (ACPF) Patient-Centered Health Literacy Advisory Board, and the study co-authors discussed the findings today at the ACP Foundation’s National Health Communication Conference in Washington, DC.

“Medication error is the most common medical mistake,” said Davis, a pioneer in the health literacy field. “Most of the research has looked at the mistakes of healthcare providers. In looking at patients, we found it was common for them to make mistakes when dosing medicine for themselves, their elderly parents, or their children.”

Despite a degree in philosophy, 61-year old Buddy Landry had trouble understanding a label for a prescription antibiotic, which allowed an infection to continue.

“The prescription was a bottle of 30 pills and it said that I could have ‘two refills over the next year,’ which I figured was in case I had a recurrence of the same problem,” said Landry. “After a week or two my infection ‘returned’ because I didn’t realize that I was supposed to refill the prescription as soon as I finished each bottle.”

Davis recommends that physicians provide specific instructions to patients about how to take the medicine.

“For example, saying ‘take one pill at 8:00 a.m. and one pill at 8:00 p.m.’ is better than saying ‘take one pill every 12 hours,’ which is confusing to a lot of patients,” said Davis.

The study indicates that currently recommended methods for confirming patient understanding, such as the “teach-back” technique in which patients are asked to repeat instructions to demonstrate their understanding, may be inadequate for identifying potential errors in medication administration.

“For those interested in improving health care quality and safety for vulnerable populations, this multisite study has important implications for practice, research, and policy,” wrote Dean Schillinger, MD, in a separate editorial. “Because the framework for regulating the content of prescription labels and accompanying materials is inadequate, patients and clinicians are suffering. With this study, the genie is out of the bottle.”

To improve health literacy, the researchers recommend that the text and format of existing primary and auxiliary labels on prescription medication containers should be redesigned and standardized. Less complex and more explicit dosing instructions may ultimately improve patient understanding. Furthermore, a system approach in which a healthcare professional verifies that patients can accurately demonstrate or articulate specific correct medication taking behaviors is important to ensure quality care.

“The study shows that patients of all ages would benefit from additional efforts to improve the clarity and comprehensibility of labeling on prescription drugs,” said Davis. “With Americans taking more prescription medications annually, the incidence of patient medication errors is likely to rise.”

The researchers noted some limitations with the study. The association between misunderstanding and medication error was not examined. Patients’ actual prescription drug-taking behaviors were not studied. The study population was at high risk for poor health outcomes. Most participants were women, and participation was limited to those who were proficient in English only.

Annals of Internal Medicine is one of the most widely cited peer-reviewed medical journals in the world. The journal has been published for 79 years and accepts only 7 percent of the original research studies submitted for publication. Annals of Internal Medicine is published by the American College of Physicians, the nation’s largest medical specialty society.

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