A Topical Emulgel with Improved Analgesic Effect: Formulation, In Vitro and In Vivo Studies

Abstract

Background

Topical analgesic drugs are used to relieve acute pain, such as strain or muscle sprains, and chronic pain, including osteoarthritis of the hand or knee, or neuropathic pain. However, currently available topical analgesics provide clinically significant relief to only a subset of patients. This work aims to develop a pharmaceutically acceptable emulsion-gel system to achieve multimodal peripheral analgesia, improve drug release rate, and accelerate the onset of action, without compromising dermal safety and physicochemical stability.

Methodology

An emulgel comprising Arnica montana extract, methyl salicylate, eucalyptus oil, menthol, capsaicin, and camphor, along with pharmaceutically acceptable excipients, was formulated and evaluated for physicochemical properties, in vitro drug release, short-term stability, in vivo analgesic efficacy, and dermal safety.

Result

The test formulation demonstrated a rapid in vitro drug release profile, appropriate physicochemical properties (pH, homogeneity, and viscosity), and superior in vivo analgesic efficacy compared with the commercially available product. No erythema or edema was observed, and the formulation remained stable under freeze-thaw and accelerated stability conditions. These findings demonstrate that the rational combination of active ingredients, targeting complementary analgesic mechanisms, within a penetration-enhancing emulgel matrix can significantly improve the therapeutic efficacy of topical analgesics.

Conclusion

The developed multi-agent emulgel formulated within a penetration-enhancing matrix demonstrates translational potential to address the unmet need in musculoskeletal pain management. Further work, including simultaneous quantification of all active components, detailed compatibility assessments, ex vivo permeability studies, and long-term assessment stability studies are warranted before clinical translation.

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Materials

The materials used for preparation of the formulation including methyl salicylate, camphor oil, menthol, eucalyptol extract, thymol extract, capsicum oleoresin extract, carbopol-934 (gelling agent), glycerin (humectant), Isopropyl myristate (penetration enhancer), liquid paraffin (oil phase vehicle), cetostearyl alcohol, E216 (propylparaben) and E218 (methyl paraben), were all purchased from Formulation Sigma-Aldrich, Germany.

Ramsha Munir, Zunaira Qureshi, Fatima Zahra, Murtaza Najabat Ali, A Topical Emulgel with Improved Analgesic Effect: Formulation, In Vitro and In Vivo Studies, Next Research, 2026, 101995, ISSN 3050-4759, https://doi.org/10.1016/j.nexres.2026.101995.