Common Errors in Measuring Liquid Medications

Almost three-quarters of caregivers surveyed in a recent study use regular flatware teaspoons to measure medicines. Household teaspoons hold from 2 to 10 milliliters of liquid. But a measuring teaspoon holds 5 milliliters of liquid. So if you measure your liquid medications with a regular teaspoon, chances are you either getting too much or too little medicine

The American Academy of Pediatrics has been recommending for 25 years that accurate dosing devices like oral dosing syringes, medicine cups, and calibrated medicine droppers and spoons should be used to give liquid medications. But there have been few studies that look at how often or how well these devices are actually used by parents. Physicians Diane J. Madlon-Kay and Frederick S. Mosch of Regions Hospital in St. Paul, Minn., and the University of Minnesota Medical School in Minneapolis designed a study to find out.

They surveyed people in the waiting areas of three primary care clinics to see which dosing devices caregivers use, and how accurately they measure medications. The research is reported in "Liquid Medication Dosing Errors" in the August 2000 issue of the Journal of Family Practice, Vol. 49, No.1

Seventy-three percent of the 130 people surveyed reported using a household teaspoon for measuring medicines at least some of the time, but most could also use more accurate devices correctly.

The participants were able to measure the proper amount of liquid using an oral dosing syringe more than 90% of the time. The authors note that the oral dosing syringe is felt to be the best device for administering liquid medications. These are relatively inexpensive and are available in a variety of sizes, but only one third of the survey participants reported having one of these at home.

Medicine cups (like the ones that come with a bottle of cough syrup) were misread by more than 10% of the participants. People confused the teaspoon and tablespoon markings on the cup, or thought that one entire cupful was the standard dose.

When interpreting dosing instructions, survey participants were usually correct when the instructions called for taking medicine three or four times a day. But in many cases, they misinterpreted instructions calling for a dose every six hours. People tended to assume that medicine should be given in six-hour intervals while awake, resulting in three daily doses, rather than the prescribed four a day. While under-dosing is less serious than overdosing, the authors note that this phenomenon could be responsible for failed treatment in some cases.

Another common error arose when the pediatric dosing chart on the medicine package was misinterpreted. In cases where a particular child did not fit into one of the age-weight categories listed on the chart, it was commonly assumed that age was the best factor in determining dosage, but the researchers stress that weight is the important criterion, not age.

Based on these survey results, the researchers encourage clinicians to promote the use of accurate dosing implements, especially oral dosing syringes. They also suggest that medication instructions should indicate the dosing interval as the number of doses per day, rather than as the number of hours between doses.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.