Liquid Dosing Accuracy Four-Times Better With Oral Syringes – Study

Researchers question the accuracy of dosing using cups commonly included with liquid drugs after finding 84% of parents measure the wrong amount of medicine and are four times more likely with cups than syringes to dose inaccurately.

The percentage of attempts with errors per parent when using a cup reached 43%, but 16.7% with a 0.2mL syringe and 16.2% with a 0.5mL oral syringe, according to a study, which found that cups “are most frequently included" with OTC products, published in the journal Pediatrics following research led by H. Shonna Yin, New York University School of Medicine Department of Pediatrics.

“Recommending oral syringes over cups, particularly for smaller doses, would be part of a comprehensive pediatric labeling and dosing strategy to reduce medication errors,” Yin and her colleagues concluded.

Conducted between August 2013 and December 2014, the research included 2,110 parents of children ages 8 and younger recruited from three urban pediatric outpatient clinics in Atlanta, New York and Stanford, Calif.

In the randomized, controlled trial, subjects randomly assigned into five groups were asked to measure medicine using various devices. Each parent measured nine doses of medication in three amounts – 2.5 mL, 5 mL and 7.5 mL – using three tools in random order, a cup and two oral syringes.

“Recommending oral syringes over cups, particularly for smaller doses, would be part of a comprehensive pediatric labeling and dosing strategy to reduce medication errors.” – Pediatrics study

The groups differed by pairings of measurement units stated on product labels and tools that contained a mix of milliliter and teaspoon measurements, including some with both on either the label or tool. The outcome measured dosing errors, determined by pediatricians using a pharmacy-grade electronic digital prescription scale to compare the measured does with a reference weight.

'Greatest' Error, Cups For Small Dosing

The researchers also found the use of dosing cups “greatly” increased the risk of errors, especially with smaller dose amounts, and overall led to more than four times the risk for error compared with syringes, the study reported.

“One reason why cups may be inferior to syringes is that the same distance along the side of the tool represents a greater volume for cups than for syringes,” the researchers noted. For example, in a cup, the distance of 1 mm might contain a volume of 0.8 mL, but on a syringe, the same measurement could hold 0.1 mL, they noted.

The researchers also said "when a cup is not held at eye level, it may appear to be filled to a particular marking when it is not.”

They also discovered that the simplification of syringes in the test bearing fewer dosage markings on them did not lead to more errors. “It may be that parents benefit so much form using a syringe over a cup that the added benefit of simplifications of markings is not discernible.”

Although the strength of associations differed somewhat by health literacy and language, the study “clearly identified certain improvements that could be made to labels and tools to enhance dosing accuracy for parents,” the researchers reported.

The researchers point out that with a significant number of parents making dosing errors using oral syringes, they recommend more intensive education of consumers by physicians, pharmacists and other health care providers, including the use of pictures and demonstrations.

FDA included both cups and syringes in a 2011 final guidance that advised OTC drug firms to provide a dosage device with their products and suggested using either teaspoons/tablespoons or metric measurements on both a product's label and its dosing device. (Also see "In Brief" - Pink Sheet, 9 May, 2011.)

The mention of cups as appropriate delivery devices also was included in guidance for liquid acetaminophen pediatric products that FDA published in August 2015. The guidance created more room for innovation than allowed in the draft versions by omitting a recommendation against potential use of droppers and including a statement that CDER will consider alternatives to calibrated cups and oral syringes. The agency also recommended marketers of those products include an appropriate delivery device including a calibrated and labeled oral syringe or dosing cup. (Also see "OTC Pediatric Acetaminophen Guidance More Flexible By Omission" - Pink Sheet, 10 Aug, 2015.)

According to the researchers, several studies have found that cups are associated with higher rates of parent errors, but they were limited in scope with respect to the range of dose amounts tested and aspects such as complexity of tool markings, said the researchers.

“Previous studies have demonstrated the superiority of syringes to cups when a 5mL dose was tested. Our study is unique in that we examined a range of doses,” they said.

The Consumer Healthcare Products Association notes that the CHPA Educational Foundation provides information to consumers on accurate dosing of OTCs and that FDA regulates drug product labels and dosing devices.

"Knowing how to properly treat children with over-the-counter medicines is so important, and this study underscores the need for parents to practice great attention and care every time they give their children medicine," said Anita Brikman, CHPA’s vice president, communications and public affairs, and executive director of the foundation, in a statement.

Teaspoon-Only Labeling: More Errors

The researcher noted their study was the first to examine, within an experimental study, whether altering specific label and dosing-tool attributes can reduce parent liquid medication dosing error rates.

The researchers found that 84% of parents made more than one dosing errors in their nine trials and that most errors were in the form of over-dosing; more with 2.5- and 7.5mL dose amounts, compared with 5-mL dose amounts.

Use of a teaspoon-only label, paired with a tool marked with milliliter and teaspoon units, was associated with more errors than pairing milliliter-only labels and tools. When syringes were used with concordant milliliter-only labels and tools, parents made one or two errors on average across the nine trials.

The American Academy of Pediatrics has suggested dosing orally administered prescription liquid medicines exclusively with labels and delivery tools marketed with milliliters to avoid confusion and dosing errors associated with common kitchen spoons, the study authors point out. The academy also recommended dosing liquid medicines to the nearest 0.1 mL, 0.5 mL or 1 mL.

AAP’s position is consistent with that of the American Pharmacists Association, which in March adopted a policy on labeling and measurement of oral liquid Rx medications to move away from “outdated” dosing cups and teaspoons in favor of oral syringes and cups that measure only in the metric system. The policy entails using milliliter as the standard unit of measure for oral liquid medications.

“Our findings suggest that health care providers should encourage oral syringe use for the measurement of liquid medications, particularly when small doses are recommended; this change would probably benefit all families, regardless of health literacy and language,” said the researchers.

From the editors of the Tan Sheet