Accuracy of Liquid Medication Dose Influenced by Size of Spoon
Page Tools
A study from Cornell University suggests that patients who continue to use household spoons to measure doses of liquid medications are likely to pour too much or too little medication, depending on the size of the spoon.
The study included 195 university students who were recent patients at a university health clinic during cold and flu season. Participants first measured a 5-mL dose of a liquid cold medication using a standard measuring teaspoon, as a “practice pour” to show them the volume of a correct dose. Participants then were asked to replicate the 5-mL dose by pouring medication into a medium-sized tablespoon (15 mL capacity) and a larger spoon (45 mL capacity) in a randomized order. Researchers measured the actual volumes poured.
The results showed that participants underestimated the correct volume by 8.4% when using the medium-sized tablespoon and overestimated it by 11.6% when using the larger spoon. These variations were attributed to “size bias”: if the size of the spoon makes the correct dose appear to be markedly more or less than 5 mL, a person typically compensates by underpouring or overpouring. (In a previous study, the researchers found that veteran bartenders poured 28% more liquor into short, wide glasses than into tall, slender glasses of the same volume.)
The bottom line for pharmacists counseling self-treating patients? Always urge patients to use the measuring device that accompanies a liquid medication. If no dosing device is provided, make certain that the patient has an accurate dosing spoon or syringe.
Ann Intern Med. 2010;152:66-7.