Misunderstanding use of medications: It may be easy to do

Pediatric clinicians are familiar with the unique challenges of administering medications orally to children. These challenges include lack of commercial availability of liquid dosage forms for many products and palatability concerns for some liquid products.

An additional challenge for the appropriate use of liquid medications is the ability of caregivers to accurately measure a prescribed dose and to accurately determine a dose of an over-the-counter medication product. Correct interpretation of OTC product package labeling, dose determination, and proper dosage form and strength are additional potential barriers of appropriate medication use.

Studies of dosing accuracy

Several published studies have evaluated the ability of parents and caregivers to accurately determine and measure a dose of medication from a liquid dosage-form product.

In a recently published study, Yin and colleagues examined 302 parents’ abilities to accurately measure 5 mL of acetaminophen suspension (Children’s Tylenol) using a variety of different dosing devices, including two dosing cups (black printed markings available with Children’s Tylenol and a dosing cup with clear etched markings), dropper, dosing spoon, oral syringe with bottle adapter and an oral syringe, given in random order to parents. Measured doses within 20% of 5 mL were considered accurate. Parents were recruited from a pediatric clinic at an urban public hospital. Acetaminophen volume doses measured by dosing cups were significantly more erroneous than volume doses measured by the other dosing devices.

Large dosing errors (>40% deviation) occurred with 23.3% to 25.8% with the use of dosing cups, compared with 1.7% to 4.6% with the use of a dropper, dosing spoon, oral syringe with bottle adapter or oral syringe. Doses were measured accurately by 30.5% to 50.2% of parents using dosing cups and by 86% to 94.4% of parents using the other dosing devices.

Health literacy of parents was additionally evaluated in this study and its relationship to use of these dosing devices. Health literacy was significantly related to large dosing errors with the use of dosing cups and dosing spoon. In a similar study, researchers evaluated the ability of 96 adults, not all of whom were caregivers of children, to accurately measure 5 mL of acetaminophen suspension using the product package dosing cup and an oral syringe. An acceptable dose was considered to be 4.5 mL to 5.5 mL. When the dosing cup was used, 14.6% of parents measured an acceptable dose compared with 66.7% of subjects using the oral syringe (P<.05). More than 85% of study participants measured an excessive dose (>5.5 mL) with the dosing cup, compared with 0% measuring an excessive dose with the oral syringe. Other studies of caregiver acetaminophen use for children have been published and have demonstrated similar findings — that caregivers are frequently unable to accurately determine a dose and measure a dose of liquid pediatric products.

In another study of three urban clinics serving a variety of socioeconomic and ethnic backgrounds, 130 adults were evaluated on the home availability and use of using seven liquid medication-dosing devices. These participants stated that a household teaspoon was most commonly (73%) used to dose liquid medications in their home, followed by a medicine cup (52%). The most frequent error reported with the use of medicine cups was mistaken measurement of 1 teaspoon instead of 1 tablespoon.

Errors with the use of dosing cups in children have previously been reported. Calls to 16 poison centers involving pediatric and adult use of liquid dosing medication cups were characterized in a 1992 publication. Of 34 cases, 79% involved a dosing error of 200% to 300%. The main dosing errors were confusion over teaspoon vs. tablespoon, an assumption that the dispensing cup was the unit of measure, and an assumption that the full dispensing cup was the actual dose.

Some evidence exists that clinicians can positively influence dosing accuracy of caregivers. McMahon evaluated three strategies of liquid antibiotic dose measurement by caregivers and assessed their accuracy. Caregivers (n=90) of children younger than 4 years who were prescribed a liquid antibiotic product for acute otitis media were evaluated. Three groups were compared: Group 1 caregivers were allowed to choose from several dosing devices they planned to use in the home; group 2 caregivers were given a dosing syringe and instructions for use; and group 3 caregivers were given a syringe with instructions for use, and in addition, a line was drawn on the syringe to indicate where the correct dose should be measured.

Caregivers were then sent to the clinic pharmacy to receive the antibiotic, and they returned to demonstrate how they would measure a dose for their child. An accurate dose was considered to be 0.2 mL of the prescribed dose. Accurate doses were prescribed by 37%, 83% and 100% of caregivers in group 1, group 2 and group 3, respectively (P<.05 for group 1 compared with groups 2 and 3). When caregivers in group 1 were allowed to choose dosing devices they would use in the home, 53% chose a dosing spoon, 20% chose a teaspoon, 17% chose a dosing syringe and 10% chose a dropper. When these caregivers demonstrated and measured a dose they would give, inaccurate doses were demonstrated by 44%, 100%, 60% and 100%, respectively.

In addition to the information on the use of liquid dose measuring devices, evidence also exists that caregivers of children can misinterpret pediatric OTC product labeling and instructions. Lokker and colleagues examined caregiver understanding of previously available “infant” OTC cough/cold products (all with package labeling instructions to consult a physician for use in children younger than 2 years). Caregivers (n=182) of infants 1 year or younger were recruited from three academic medical centers and were assessed on the potential use of four (no longer available) pediatric OTC cough/cold products.

These caregivers were evaluated on how they interpreted and would potentially use the selected products (eg, “Would you give this medicine to a 13-month old infant?”). When these subjects viewed the product package fronts, 86% of the caregivers indicated that the product was appropriate to give to infants younger than 2 years. When the caregivers were allowed to view the entire product packages, 51% of responses included that it was appropriate to give these products to a 13-month old infant, despite the package labeling stating to consult a physician before administration to children younger than 24 months. Common features of product packaging that affected caregiver perception of age indication included use of the word “infant” and infant-related pictures or graphics on the package, such as teddy bears or drawings of infants.

Product misuse and harm

Various case reports suggest that misinterpretations of product labeling or inaccurate liquid product dosing have been important factors in causing significant harm or death in infants and children given liquid OTC pediatric products. Acetaminophen is the most commonly administered medication to infants and children and its inappropriate use has resulted in case reports of harm.

The FDA is currently evaluating various strategies to improve the safe use of acetaminophen in children and adults. Factors that have contributed to the inappropriate and harmful use of acetaminophen products in infants and children have included use of inappropriate age-indicated products and concentrations/strengths. Studies have shown that some parents are not aware of differences in strengths of pediatric infant’s and children’s acetaminophen products, and some parents said they believed that the children’s liquid products were more concentrated than infant liquid products.

Case reports of hepatotoxicity due to unintentional but inappropriate use of acetaminophen in children have shown that, in these cases, parents used inappropriate dose measuring devices (eg, use of teaspoon instead of a dropper) or used adult-strength and not pediatric-strength products. There is also evidence of harm from the use of OTC pediatric cough/cold products, and this information is partly responsible for the recent withdraw and use reassessment of products for children.

Conclusions

Evidence exists that parents and caregivers are not always able to determine an appropriate dose and dosage form or accurately measure a liquid dose of OTC and prescription medication products. Pediatric clinicians should be aware of the potential for these medication errors when recommending medications for infants and children.

Education of caregivers about these issues is important and should include a discussion and specification of product dosage form, dose (milligram and volume dose), dosing schedule and therapeutic goals of product use. Dosing syringes can be provided in the clinic and pharmacy settings, with demonstration of proper use. Assumptions that caregivers are able to choose an appropriate product and determine/measure an appropriate dose for their child can prove to be false.

Edward Bell, PharmD, BCPS, is a Professor of Clinical Sciences at Drake University College of Pharmacy, Blank Children’s Hospital and Clinics in Des Moines, Iowa.

For more information:

• Heubi JE. J Pediatr. 1998;132:22-27.
• Li SF. Pediatric Emergency Care. 2000;16:394-397.
• Litovitz T. Annals Pharmaco. 1992;26:917-918.
• Lokker N. Pediatrics. 2009;123:1464-71.
• McMahon SR. Pediatrics. 1997;100:330-333.
• Sobhani P. Annals Pharmacother. 2008;42:46-51.
• Yin HS. Arch Pediatr Adol Med. 2010;164:181-186.