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Dosing errors persist in liquid medication for children
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Over the past 5 years, several studies have been published describing how oral liquid drug dosing devices and units of measure can impact dosing accuracy. While seemingly conveying simple instructions and straight forward actions, differing dosing devices and units of measure can make this process anything but, especially when these methods vary between health care providers, pharmaceutical manufacturers of pediatric over-the-counter products, pharmacies and parents.
Varying degrees of precision
The latest published study on this topic by Yin et al sought to characterize the extent to which liquid medication dosing errors by parents were affected by discordant dosing units of measure on the prescription bottle label and the dosing device. Parents (n=2,110) of children aged 8 years from three pediatric clinics in different states were randomized to one of five study groups, which differed by prescription drug bottle label directions and dosing device. Each parent was asked to measure nine doses of drug as: three different amounts (2.5 mL, 5 mL, 7.5 mL) using three different devices (cup, oral syringe in 0.2 mL increments, and an oral syringe in 0.5 mL increments).
The groups differed by the pairing of dosing unit directions listed on the bottle label and the dosing device. Group 1 included mL units on the label and dosing device, and was considered the gold standard scenario. Group 2 included both mL and tsp units on the label and the dosing device. The other groups differed by combinations of units expressed as “mL, tsp, or teaspoon.” The primary outcome measure was dosing error, defined as >20% deviation from the labeled dose.
A total of 84.4% of parents made 1 dosing errors in their nine attempts and 21% of parents made 1 large dosing errors, defined as >2x the intended dose. On average, parents made dosing errors in 25.3% of attempts, and 68% of errors were overdoses. Group 1 parents (mL units only on the label and dosing device) most accurately measured doses. Cups were the least accurate measuring device, as more parents made dosing errors using cups than using an oral syringe (>4x odds of error). This study demonstrates that mL-only markings on drug bottle labels and dosing devices are most accurate for dose measurement, and that even when mL units are used, dose measurement errors commonly occur by parents.
A hazy definition of ‘spoonful’
Dr. Yin and other researchers have published additional studies relevant to liquid drug dose measurement accuracy and implementation by parents. These studies share similar findings and conclusions on liquid dose measurement prescribing labeling, and measurement by parents. A common finding in these studies is the commonality of dosing errors committed by parents when observed for liquid product and dosing device actual use: approximately 30% to 50% of parents inaccurately measured doses in these studies, with many of these errors described as large errors (100% or greater).
Several observational studies have demonstrated that when drug bottle labels are expressed in teaspoon or tablespoon units, dosing errors by parents increase, and dose measurement accuracy decreases when parents voluntarily chose teaspoon or tablespoon devices to measure liquid doses. When liquid products are labeled with mL only units, dosing accuracy increases.
These studies additionally share a conclusion that oral dosing syringes are more accurately used by parents to measure liquid drug doses as compared to use of dosing cups, especially for smaller volume doses. Dosing cups may be acceptable dose devices to use when larger liquid volumes are prescribed, although this has not been adequately studied and evaluated. Other studies related to this topic, including pharmacy analysis, demonstrate that pharmacy label dosing units may not always reflect how liquid medication prescriptions are written.
A study of 649 prescriptions of commonly prescribed liquid drug products for young children among four community pharmacies in Philadelphia in 2012 revealed that 24% of prescriptions were written with teaspoon-only units, and 28.5% of all drug bottle labels were dispensed using teaspoon-only units. This study provides interesting data, although these data were collected prior to publication of the AAP policy recommendation on use of mL as the sole volumetric dosing measure in 2015, described below.
Another pharmacy study evaluated dosing devices available and given to parents from 22 pharmacies in the Tulsa, Oklahoma, area in 2012. A total of 58 dosing devices were collected, with oral dosing syringes of different sizes (ranging from 1 mL-10 mL) most commonly available; were available dosing spoons, droppers, and cups as well. Most of the delivery devices (79%) displayed mL and tsp, and only 12% displayed mL only.
Regulations and standards
In 2015, the AAP published guidelines endorsing the milliliter as the only liquid volume unit of measurement that should be used in all aspects of pediatric liquid drug prescribing, product manufacture, dispensing and administration. According to the AAP guidelines, other units of measure, especially “teaspoon; tsp” and “tablespoon; tbsp” should not be used; the guidelines also highlighted a preference for oral syringes as a dose measurement device for parents, and avoidance of home or kitchen teaspoons and tablespoons.
An area related to the ease and accuracy of use of oral liquid drug product and dosing that has shown significant change and improvement is OTC pediatric liquid drug product manufacturing. In 2011, the FDA issued final voluntary guidelines directed at product improvement for pharmaceutical manufacturers of liquid OTC drug products; similar recommendations were issued the previous year by the trade group representing these pharmaceutical manufacturers.
Among the FDA recommendations were guidelines directed at inclusion of a dosing device with each liquid drug product, and consistency of product dosing device markings and product package labeling, among others. In 2010, a valuable study was published by Yin and colleagues, that analyzed 200 pediatric oral liquid OTC products for various characteristics assessing the potential for inaccuracy of product use. This study revealed that 98.6% of products packaged with a dosing device had at least one inconsistency between product dosing directions and the included dosing device, in addition to other product characteristics potentially confusing to parents. Additionally, several products (26%) were not packaged with a dosing device.
Published studies have documented the difficulties and inaccuracies many parents have with dosing liquid medications for their children. As all drugs have potential for dose-related adverse effects, especially drugs considered to have a narrow therapeutic index, these difficulties may have clinically significant results. In recent years, OTC pediatric oral liquid drug products have improved with respect to dosing clarity and ease, although further improvements to simplify and clarify product dosing directions and measurement are needed.
Several studies have demonstrated that specific counseling strategies given to parents by health care professionals, including dosing device use demonstration and teach-back, can significantly reduce the likelihood of parent dosing errors. Recent national recommendations have called for milliliters to be the only oral liquid dose unit of measure. It is best if physicians, other prescribing health care professionals, and pharmacists, can offer and state dosing directions, along with appropriate dosing oral syringes, with mL as the sole dosing unit of measure.
- References:
- AAP Committee on Drugs. Pediatrics. 2015; doi: 10.1542/peds.2015-0072.
- Budnitz DS, et al. Pediatrics. 2014; doi:10.1542/peds.2013-2362.
- Honey BL. Clin Pediatr. 2013; doi: 10.1177/0009922813479160.
- Shah R. J Pediatr. 2014; doi: 10.1016/j.jpeds.2013.11.007.
- Yin HS, et al. JAMA. 2010; doi:10.1001/jama.2010.1797.
- Yin HS, et al. Pediatrics. 2016; doi: 10.1542/peds.2016-0357.
- For more information:
- Edward A. Bell, PharmD, BCPS, is a professor of pharmacy practice at Drake University College of Pharmacy and Health Sciences and Blank Children’s Hospital and Clinics, Des Moines, Iowa. He also is a member of the Infectious Diseases in Children Editorial Board. Bell can be reached at ed.bell@drake.edu.
Disclosure: Bell reports no relevant financial disclosures.