Abstract
The palatability of pediatric pharmaceutical products plays a crucial role of influencing medication compliance. Rejection of unpalatable medications can potentially lead to treatment failure which can have immediate and delayed consequences. With advances in both the food and pharmaceutical industries, the systematic assessment of palatability has gained importance. Various methods such as visual analogue scales, facial hedonic scales, and facial recognition software, have been employed to assess palatability. While proven to be useful, these methods have significant limitations and may not be workable for young children. Despite these advancements, a universally accepted “gold standard” for assessing pediatric mediation palatability, recognized by drug regulatory agencies, is yet to be established.
Introduction
As recently reviewed by Peng et al. (), the palatability of pediatric pharmaceutical products for children can adversely influence medication compliance. The rejection of unpalatable pharmaceutical products can negatively impact therapeutic adherence which, in turn can lead to treatment failure which may have both immediate consequences (e.g., in the case of oral liquid antimicrobials, persistence of disease) and potentially, delayed consequences (e.g., fostering antibiotic resistance) (–) In a survey of drug administration methods and their relationship to compliance (), reported that more than 50% of children aged 6 years or less had difficulty swallowing oral drug formulations. Potential contributing factors include the size and shape of a given solid oral drug formulation and in the case of both solids and liquids, factors related to palatability such as taste, flavor, and smell (–).
Evaluation of drug palatability and patient acceptance has been done using both in vitro and in vivo evaluations and has become increasingly important (). Several methods have been developed and applied for palatability assessment () which includes, visual analog scales (), facial hedonic scales (), use of an electronic tongue () and more recently, the use of facial recognition software (). Despite these advancements, there appears to be no generally accepted “gold standard” method for palatability assessment in children that has been universally adopted by drug manufacturers or regulatory agencies. In this mini-review, our goal is to provide the reader with a review of the biologic determinants of palatability and also, the existing methods used to assess it in children.
Background
Palatability is a subjective measure of how pleasant a food or drug substance is to consume. It is influenced by a variety of organoleptic factors which are sensory in nature, individually determined, and most often associated with a specific substance/product. Factors that can influence palatability (Google BARD:
https://bard.google.com; accessed 25 October 2023) include the following:
Sensory Factors (e.g., taste, texture, temperature, visual appearance)
Individual Factors (e.g., age, culture, health status, psychological)
Product Factors (e.g., physical form, additives, colorants)
Also, it is possible that the patient environment may also be a contributing factor in the assessment of drug palatability in pediatric patients (e.g., a calm, reassuring environment without distractions being preferrable).
Generally speaking, palatability is purely a subjective experience. What one person finds palatable another person may find unpalatable or objectionable. Additionally, palatability can change over time. For example, a person may develop a taste for a food or drug after repeated exposure or alternatively, taste preference can often change with aging. Finally, taste involves a complex interaction between olfaction, biological perception of flavor and mouthfeel of the substance being tasted ().
Relevant biology of human taste
The role of olfaction in taste perception
The sense of smell is a major determinant of perceived taste of a given substance. Without our sense of smell, our sense of taste is limited to only five distinct sensations: sweet, salty, sour, bitter and “umami” or savory sensation. Consequently, olfaction is relevant as a sense in the acceptance of orally administered medications.
As reviewed by Czarnecki and Fontanini (), odors have a dual relationship with taste: they can either precede it or accompany it. The former happens when we smell the aroma of the food in front of us through what is known as oronasal smelling. The latter happens when food in the mouth liberates volatile molecules that are carried by air through the pharynx into the nose, a process called retro-nasal smelling. Retronasal olfactory stimulation appears to be bidirectional in that it inextricably links smell and taste perception as overall components of taste sensation.
The two streams of chemosensory information regulating olfaction and taste have a complex interaction and their interplay occurs well before signals reach the orbitofrontal cortex of the brain (). Neurons in the gustatory cortex can respond to odors and those in the olfactory cortex can respond to taste (). The basic biology of olfaction is illustrated in Figure 1A and very recently, “taste coding” at a biomolecular level has been extensively reviewed by Roper ().
Figure 1
Determinants of the human sensation of taste
Human taste is characterized by 5 qualities including sweet, sour, salty, bitter, and umami (savory) (
The sweet receptor is composed of two proteins (T1R2 and T1R3) that are encoded by the associated genes TAS1R2 and TAS1R3, respectively. These two known sweet receptors function as G-protein coupled receptors that act via the IP3/cAMP pathway to release calcium from the endoplasmic reticulum, resulting in depolarization of the taste cell and release of neurotransmitter (
Genetic polymorphisms in taste receptors may contribute for some of the inter-individual differences in taste perception. For example, TAS2R38, a polymorphically expressed gene that modulates bitter taste sensation (
Teleologically, bitter taste perception was believed to protect humans from the intake of some poisonous substances during nutritional sustenance. Similarly, the ability to detect acidic taste can help maintain acid-base balance in the body by regulating the ingestion of acids. Similarly, the perception of salty taste facilitates discrimination against excessive sodium intake which facilitates homeostatic regulation of water balance, pH, conductance, and osmotic pressure (
Finally, as recently reviewed by D'Urso and Drago (
Mouth feel—the role of viscosity on taste perception
The flavor of a given food and/or medication is only one factor when considering patient acceptance. Another important organoleptic property of taste is mouth feel, the oral sensations produced by a particular food which is dependent on many different characteristics (
Attempts have been made to describe the relationship between the mouthfeel of liquid foods and their rheology (
On the human tongue, the viscosity of a liquid is detected by filiform papillae (
Methods for assessing palatability of liquids in children
For nearly 3 decades, age-appropriate hedonic scales have been used to measure food preferences in young children (
In this younger age range (3–7 years of age), where reduced cognitive and neurodevelopmental statuses are normally present, other strategies such as facial recognition technology may have utility in an experimental setting (
The limitations seen with the aforementioned methods required the development of a more age-appropriate, patient-friendly, and reliable method to assess palatability (taste preference/patient acceptance), especially in very young children. To fill this gap, the TASTY scale has been newly created as a self-report taste rating scale to be utilized for palatability testing, particularly in younger children. The goal of creating this scale, in part, was to separate the perceptions of taste from emotion, which is commonly seen in existing faces scales (Figure 2) (
Figure 2

Seven-face and five-face study scales presented to subjects aged 5 years and older. Top to bottom: TASTY Scale (
Future directions
Although the Visual Analogue Scale (VAS) and facial hedonic scales continue to be widely used for the development and evaluation of liquid medications for children, they lack formal validation, are not appropriate for use in very young children (i.e., the population most likely to consume oral liquid medicines), and offer limited substantiation of the association between the palatability of medicines and pediatric adherence to treatment regimens (
Wide adoption of a single, standardized scale as the “gold standard” for assessing palatability of liquid drug formulations in infants and young children would enhance the reliability of outcomes across and between pediatric studies of palatability. Moreover, this would enable the relationship between medication palatability and pediatric adherence to be more robustly and conclusively tested. A unified, standard approach could potentially enhance the goals of pediatric drug therapy which, in turn, have the potential to improve health outcomes, mitigate therapeutic failures and lower health care costs. Most importantly, enhancing patient well-being improves the quality of life for the pediatric patient and their families.
Conclusions
It is well recognized that the acceptability of a given medicine by a child is directly related to the drug formulation (
Finally, with pediatric drug development and regulation becoming increasingly a global exercise facilitated by harmonization of effort, the same goals are applicable regarding the tools/techniques used to assess palatability of drugs in pediatric patients. Realization of this goal has the potential to markedly improve pediatric drug development and thereby, the health of children everywhere.
Statements
Author contributions
HS: Investigation, Writing – original draft, Writing – review & editing, Conceptualization, Resources. CL: Conceptualization, Writing – review & editing, Writing – original draft, Investigation, Resources. TD: Writing – review & editing. JM: Writing – review & editing. GK: Conceptualization, Funding acquisition, Project administration, Supervision, Visualization, Writing – original draft, Writing – review & editing.
Funding
The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.
The resources necessary to produce this paper were provided through the Burnett School of Medicine at Texas Christian University.
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Publisher’s note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
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Summary
Keywords
medicine, palatability, taste physiology, viscosity, children
Citation
Schluterman HM, Linardos CG, Drulia T, Marshall JD and Kearns GL (2024) Evaluating palatability in young children: a mini-review of relevant physiology and assessment techniques. Front. Pediatr. 12:1350662. doi: 10.3389/fped.2024.1350662
Received
05 December 2023
Accepted
25 January 2024
Published
08 February 2024
Volume
12 - 2024
Edited by
Karel Allegaert, KU Leuven, Belgium
Reviewed by
Jumpei Saito, National Center for Child Health and Development (NCCHD), Japan
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Copyright
© 2024 Schluterman, Linardos, Drulia, Marshall and Kearns.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Gregory L. Kearns g.kearns@tcu.edu
Disclaimer
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.