Colour of Medicines and Children’s Acceptability? A Systematic Literature Review of Children’s Perceptions about Colours of Oral Dosage Forms †

The colour of a product plays an important role in consumer experiences, and in the context of pharmaceutical products, this could potentially affect a patient’s expectations, behaviours, and adherence. Several studies have been conducted on adults, but little is known about children’s opinions on colours of medicines and to what extent medicines’ colour affects their acceptability. To address this gap, a systematic search in PubMed, Scopus, MEDLINE, and Web of Science was conducted. Two authors independently screened the titles, abstracts, and references of all articles and selected studies conducted on children (0–18 years old), assessing children’s preferences or opinions about colour of oral dosage forms as either a primary or secondary objective or as an anecdotal record. A total of 989 publications were identified and, after screening, 18 publications were included in the review. Red and pink were the most liked colours and there appeared to be a relationship between the colour of a medicine and expected taste/flavour. The review also highlighted a scarcity of information, usually collected as an anecdotal record. Several gaps in the current knowledge were underlined, emphasizing the need of patient-centred studies to understand if the use of certain colours can improve or worsen the acceptability of a paediatric medicine. This will help inform pharmaceutical manufacturers and regulators on the role and need of colours in children’s medicines beyond quality purposes.

1. Introduction

Colour plays an important role in consumer experiences, and in general, it is estimated that around 60% to 90% of a product assessment is usually based on colour alone [1]. This highlights the crucial role of colour and its ability to influence consumers’ perceptions about a product [2]. Thus, colour psychology is widely used in market research for the design of food and drink packaging, clothing, and much more [3].

In the pharmaceutical field, colouring agents are organoleptic excipients that are frequently added to pharmaceutical products [4], and their use is strictly regulated. In Europe, the use of colouring agents in medicinal products is governed by a specific directive (Directive 2009/35/EC of the European Parliament and of the Council) [5], and in the United States, the Federal Food, Drug, and Cosmetic Act (Chapter VII, Section 721) specifies that any colouring agent is subject to FDA approval before its use in drugs [6]. Likewise in Japan, the Ministry of Health, Labour, and Welfare and in Canada, the Government of Canada are responsible for defining and maintaining specifications [7]. These rules are to guarantee a safe and appropriate use of colouring agents.

Reasons for adding colour to a medicinal product are several: for improving brand recognition and to protect a product’s identity against generic competition [8,9], to help end-users recognise and differentiate medicines, including dose strengths, particularly when taking several medications [10]. Furthermore, colour can be associated with consumers’ perceptions affecting medicine efficacy via a placebo effect and triggering various emotional responses [11]. For example, red pills are generally considered stimulating, whereas blue pills are associated with a depressing or tranquilizing function [12,13,14]. Colour additives can also be used for formulation purposes, for example, to provide opacity to light sensitive active ingredients [15], or to match the visual appearance with the appropriate flavour of the formulation.

However, most of the research assessing the effects elicited by colours of medicines on the users has been limited to the adult population. Children are even more sensitive than adults to sensory characteristics such as taste, size, or colour. It is known that children tend to like colours that match their own preferences [16,17], and these seem to lean towards bright colours particularly in young children, because these colours proved to evoke positive emotions (e.g., happiness) in children [16,17,18,19,20,21].

In recent years, there has been an increasing focus on making medicines for children more tailored for them and assessing a product acceptability has now become an integral part of the product development. Acceptability is defined as the overall ability and willingness of the patient and caregiver to use a medicinal product as intended. Acceptability is determined by the characteristics of the users and the product, and it is likely to have a significant impact on the patient’s adherence and, consequently, on safety and efficacy of the product [22]. The importance and need to study the acceptability of paediatric formulations was discussed in an EMA Reflection Paper [23] and endorsed in the latest EMA Paediatric guideline on pharmaceutical development of formulations for paediatric use [22], leading to more studies being conducted to evaluate product characteristics affecting acceptability and, in particular, palatability [24]. The appearance, including the colour, of a medicinal product is listed among the product characteristics influencing acceptability. However, knowledge about how children perceive colours of oral medicines and whether some colours could positively or negatively affect children’s acceptance for oral dosage forms, and to what extent, is lacking.

The use of a colouring agent in a paediatric product must be justified in terms of its safety in the proposed patient population, and potential benefits, including, for example, avoiding potential dosing errors and improved organoleptic acceptability [22]. Harnessing children’s views on their preferences could lead formulators to develop more acceptable medicines to them and enable informed decision-making regarding the need for or use for colours in paediatric products. Thus, the aim of this qualitative systematic review was to identify and collect available data about children’s views and preferences for colour of oral medicines from existing literature. These data will be used to assess to what extent this sensory attribute affects the overall medicine acceptability, and to identify any trend in terms of colour preferences among the paediatric population to understand which colours are preferable and which would need to be avoided to make a paediatric medicinal product more appealing. It will also be useful to identify any gaps in the current knowledge to be addressed by future studies.
This work was carried out by the conect4children (https://conect4children.org/, c4c (accessed on 8 June 2023)) Formulation Expert Group. c4c is a public–private consortium funded by the Innovative Medicines Initiative 2 to create a sustainable infrastructure promoting innovation in the design and conduct of paediatric clinical trials. The c4c Formulation Expert Group is one of the c4c methodology expert groups, and their focus is on formulation for children, providing advice on formulation aspects during children’s drug development. This study was carried out by the group for learning and providing new knowledge about how to further improve paediatric formulations, as this is important for the development of better medicines for children.

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Alessandrini, E.; Gonakova, M.; Batchelor, H.; Gizurarson, S.; Iurian, S.; Klein, S.; Schaufelberger, D.; Turner, R.; Walsh, J.; Tuleu, C. Colour of Medicines and Children’s Acceptability? A Systematic Literature Review of Children’s Perceptions about Colours of Oral Dosage Forms. Pharmaceutics 2023, 15, 1992.
https://doi.org/10.3390/pharmaceutics15071992