(T1230-08-54) Enhancing Patient Experience in Topical Formulations: A Sensory-Based Strategy Using Rheology Modifiers and Emollients

Purpose: Patients are seeking topical drug products with a less medicinal feel, as current formulations often have undesirable cosmetic properties [1] and induce skin irritation [2] [3] leading to poor compliance, reduced treatment efficacy and raised healthcare costs. To address these issues, there is a growing need to enhance product feel, absorption and appearance. Carbopol® polymers, when used in topical formulations, offer customizable rheological properties and help create non-greasy creams and gels with enhanced aesthetics and sensory appeal. In addition to pharmaceutical excipients, other ingredients found in the FDA Inactive Ingredient Database (IID), such as emollients, emulsifiers, and humectants, also provide similar benefits. To investigate the impact of combining gelling agents and emollients on the sensory attributes of topical drug formulations, this study utilized the SensiMap™ framework (Figure 1A)—a formulation concept developed as a straightforward tool for tailoring sensorial properties in cosmetic emulsion systems [4]. By applying this approach to pharmaceutical topical formulations, we aimed to characterize and differentiate sensory properties in a structured, data-driven manner.

Methods: Formulation Preparation: Six simple oil-in-water emulsions were prepared using combinations of rheology modifiers and emollients for sensory evaluation (Table 1). Each formulation contained deionized water, Carbopol® polymer (Carbopol® Ultrez 10 NF or Carbopol® ETD 2020 NF polymer), emollient (Schercemol™ DIA ester, Schercemol™ 1688 ester, or mineral oil (MO)), emulsifiers (Glucamate™ SSE-20 and Glucate™ SS emulsifier), sodium hydroxide as neutralizer and phenoxyethanol as preservative. The Carbopol® polymer was incorporated at levels ranging from 0.35-0.7 wt% and sodium hydroxide was used to achieve consistent pH (6.0–6.5) and viscosity (30,000–35,000 cP; Brookfield RVT, spindle #6, 20 rpm). Sensory Evaluation: A paired comparison (directional difference) test was conducted using a trained sensory panel to evaluate the six formulations featuring varied Carbopol® polymer–emollient combinations. Prior to formal assessments, panelists received a handout outlining key sensory attributes and definitions and practiced using designated training samples (0 and 10 intensity references). The same amount of two formulations was applied to opposite forearms and rubbed in equal-sized areas until absorbed. At the rub-out stage, attributes such as quick break, spreadability, richness and absorbency were assessed. Emolliency was evaluated at afterfeel stage.

Results: The sensory contribution continuum (Figure 1B) outlines three stages of sensorial perception when applying topical formulations: Rubout I, dominated by aqueous (external) phase; Rubout II, the non-aqueous (internal) phase begins to dominate; and Afterfeel, dominated by the non-aqueous phase. This model reflected the contribution of a particular ingredient (Carbopol® polymer or Schercemol™ ester) on the intensity of the skinfeel. Comparisons of formulations containing different Carbopol® grades (Figure 2A) revealed that during the rub-out stage, Carbopol® Ultrez 10 (higher degree of crosslinking) was perceived by over 80% of panelists as providing a quicker break, by more than 70% as offering greater spreadability, and by over 90% as being less rich than Carbopol® ETD 2020 (medium degree of crosslinking and hydrophobic moieties). The level of crosslinking and the chemical composition of the Carbopol® polymers determined their salt tolerance, which was the primary factor influencing these sensory differences. On the other hand, emollients showed a more dominant impact on attributes such as absorbency and emolliency in the later stages of sensory contribution continuum (Figure 1B). Formulations with light esters, such as Schercemol™ DIA (F1), were associated with higher absorbency (70% of panelists) and lower perceived emolliency (80% of panelists) compared to those with heavier emollients like Schercemol™ 1688 and mineral oil (Figure 2B). When compared to mineral oil-based formulations (F7 and F8), absorbency remained similar regardless of Carbopol® grade, but emolliency perception increased (60% and 70% of panelists, respectively; Figure 2B). Esters such as Schercemol™ with a broad spectrum of emolliency can offer a range of sensory experience and are designed to reduce the greasiness associated with mineral oil.

Conclusion: Formulations using Carbopol® polymers and Schercemol™ esters demonstrated that sensorial attributes of pharmaceutical topicals can be intentionally designed to enhance patient experience. Highly crosslinked Carbopol® grades promote quick break and clean afterfeel, while lower crosslinked types add richness and cushion. Light Schercemol™ esters improve absorbency, and richer variants extend emolliency. Utilizing unique combinations of Carbopol® polymers and Schercemol™ ester emollients, guided by a matrix known as SensiMap™, a formulator can customize sensory properties to develop patient-centric pharmaceutical topical products.

References: [1] Jorge et al. "Topical preparations for pain relief: efficacy and patient adherence," Journey of pain research, vol. 4, pp. 11-24, 2010.
[2] Devaux et al. "Adherence to topical treatment in psoriasis: a systematic literature review," J Eur Acad Dermatol Venereol, vol. 26, no. s3, pp. 61-67, 2012.
[3] Chovatiya et al. "Factors Affecting Patients Adherence in Topical Therapies," Dermatology Times, vol. 43, no. 7, 2022.
[4] Carey et al. "A New Formulators' Tool for Customizing Sensory," Cosmetics&Toiletries, 2013. https://www.cosmeticsandtoiletries.com/cosmetic-ingredients/sensory/article/21835951/a-new-formulators-tool-for-customizing-sensory

Table 1. Emulsions for sensory evaluation.

Figure 1. (A) SensiMap™ sensory combination matrix of Carbopol® polymers and emollients. (B) The sensory contribution continuum of formulations containing Carbopol® polymers and Schercemol™ ester emollients.

Figure 2. (A) Evaluation of sensory attributes (quick break, spreadability and richness) in rub out stage. (B) Evaluation of sensory attributes, absorbency in rub out stage and emolliency in afterfeel stage.