Despite the availability of pharmacy-approved dosing cups, droppers, spoons, and syringes, many patients and caregivers are still tempted to reach for the nearest kitchen spoon when administering liquid OTC or prescription medicines. The FDA discourages the practice, and research indicates that it may increase the risk of dosing errors by even the most confident caregiver.
Led by Brian Wansink, PhD, author of Mindless Eating: Why We Eat More Than We Think, a team of researchers from Cornell University examined the influence of spoon size on college students’ powers of estimation. A total of 195 participants were first asked to pour exactly 1 teaspoon (5 mL) of liquid cold medicine into a regular teaspoon. Students were then asked to pour the exact same dose into a second medium-sized tablespoon, then a third larger spoon. Following the experiment, researchers asked the students how secure they were in the accuracy and efficacy of the doses they poured.
Although most students were confident they had poured the right amount, researchers found that their dosages varied directly according to spoon size. When using the larger spoon, participants overdosed by 11.6%; when using the smaller spoon, they underdosed by 8.4%.
"Although these educated participants had poured in a well-lit room after a practice pour, they were unaware of these biases and were confident that they had poured the correct doses in both spoons," the researchers wrote.
Since most cold medications are taken every 4 to 8 hours for the duration of a patient’s illness, frequent under- or overdosing, even by seemingly insignificant amounts, can have a strong cumulative impact. The researchers also identified spoon dosing as a major cause of pediatric poisonings and emphasized the importance of patient education to increase awareness of the problem. The findings were reported in the January 5, 2010 issue of the Annals of Internal Medicine.
Pharmacists can prevent measuring errors by ensuring patients have access to accurate measuring devices, and that all devices are marked in units that match those specified by the dosing instructions. Before releasing liquid medications, pharmacists should also remind patients and caregivers—who may be overconfident in their guessing abilities—to faithfully use the approved measuring device when pouring doses for themselves or their families.