Accuracy of Oral Liquid Measuring Devices: Comparison of Dosing Cup and Oral Dosing Syringe

Parisa Sobhani, PharmD; Jaydi Christopherson, PharmD; Peter J Ambrose, PharmD FASHP; Robin L Corelli, PharmD


The Annals of Pharmacotherapy. 2008;42(1):46-52. 

In This Article

Abstract and Introduction

Background: Previous studies have found that teaspoons are commonly used to administer liquid medications to children. The capacity of household teaspoons ranges from 1.5 mL to 9 mL, potentially leading to errors in dosing. There are few studies evaluating alternative measuring devices.
Objective: To assess adult consumers' previous experience with measuring devices for oral liquids, compare the accuracy of an oral syringe with that of a dosing cup, and determine consumer perceptions of accuracy and ease of use of an oral syringe and a dosing cup.
Methods: Individuals at least 18 years of age were shown a picture of 5 commonly used measurement devices and asked their perceptions of and experience with the devices. They were then asked to measure a 5 mL (1 teaspoon) dose of Tylenol (acetaminophen) suspension, using the EZY Dose oral syringe and the dosing cup provided by the manufacturer. An acceptable dose was defined as 5.0 ± 0.5 mL. Following the measurement, participants completed a 5 item survey that assessed their perceptions of the accuracy and ease of use of the syringe and dosing cup.
Results: A total of 96 subjects completed the study. Participants more commonly reported use of droppers (68%), dosing cups (67%), and teaspoons (62%) versus cylindrical spoons (49%) or oral syringes (49%) for measuring oral liquids. Sixty-four (66.7%) subjects measured an acceptable dose using the syringe versus 14 subjects (14.6%) using the cup (p < 0.001). The mean volumes ± SD measured with the syringe and cup were 4.5 ± 0.7 mL and 6.3 ± 0.7 mL, respectively (p < 0.001). After using both devices, the majority of subjects believed that the syringe (80%) and cup (71%) would measure an accurate dose. Most (87%) participants perceived that the cup was easy to use; 63% believed that the syringe was easy to use.
Conclusions: Droppers and dosing cups were the most commonly used devices in the home for measuring liquid medications. Subjects were more likely to measure an acceptable dose with an oral syringe when compared with a dosing cup. However, a large proportion of study participants were unable to measure an accurate dose with either device. Community pharmacists should educate caregivers on the selection and proper use of measuring devices to improve the accuracy of medication administration in the home.

Many prescription and over-the-counter (OTC) medications are available in liquid formulations. Considering that more than 50% of 3-year-old children have received at least one OTC product, the potential for dosing and administration errors is great.[1] In an observational study, Li et al.[2] found that dosages of acetaminophen administered by parents were inaccurate 62% of the time due to both over- and underdosing. Not only are there multiple OTC liquid products and concentration differences among the same medications; there are also numerous measuring devices available, further amplifying the potential for medication errors.[3] Moreover, the pediatric population itself poses a challenge because of weight-based dosing.[4]

The subject of administration errors associated with measuring devices is not a new issue. In 1975, Mattar et al.[5] found that when liquid antibiotics or oral decongestants were not dispensed with a measuring device, 75% of parents used a household teaspoon or kitchen measuring spoon to administer the medication to their children. A 1992 report from the American Association of Poison Control Centers found that liquid drug dosing errors were commonly caused by teaspoon/tablespoon confusion and the assumption that the entire dosing cup (eg, filled to capacity) was the recommended dose.[6] Furthermore, the measured capacity of a household teaspoon is highly variable, ranging from 1.5 mL to 9 mL, which may lead to inaccuracies in administering liquid medications.[5,7] Potentially more accurate measuring devices include oral syringes, medication cups, cylindrical spoons, and droppers, when used appropriately.

Acetaminophen is one of the OTC products most commonly purchased by US consumers.[8] Although acetaminophen is generally considered to be a safe and effective agent, one study found that 42% of admissions for acute liver failure among tertiary care medical centers in the US were associated with acetaminophen overdose.[9] Most cases of accidental overdose among children are caused by the caregiver's failure to read and understand the label instructions or use of an inappropriate (eg, more concentrated) preparation or incorrect measuring device.[10] In one study, 6% of parents believed that acetaminophen was safe enough to give in unlimited amounts and nearly a third of parents gave more than the recommended dose of acetaminophen to their children.[11]

Few studies evaluating techniques to prevent medication errors associated with liquid measuring devices have been conducted with consumers,[12,13,14,15] and further efforts to identify effective strategies to improve the accuracy of oral liquid medication administration in the home setting are warranted.

Our study objectives were to assess adult consumers' previous experiences with oral liquid measuring devices, compare the accuracy of an oral syringe and dosing cup when used by adults, and determine consumer perceptions regarding the accuracy and ease of use of an oral syringe and a dosing cup.


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