Evaluation of diclofenac sodium creams formulated using extracted castor oil (Ricinus communis L.)

This study evaluated the formulation and physicochemical properties of diclofenac sodium cream using castor oil (Ricinus communis L.) extracted from seeds cultivated in Abraka, Nigeria. Diclofenac sodium, a non-steroidal anti-inflammatory drug (NSAID), is commonly used for managing pain and inflammation but is associated with gastrointestinal side effects when administered orally. Topical formulations, such as creams, can mitigate these adverse effects while providing targeted drug delivery. Castor oil, known for its high viscosity and unique chemical profile rich in ricinoleic acid, was extracted via solvent extraction and utilized as the oil phase in various cream formulations. The creams were assessed for pH, viscosity, spreadability, homogeneity, emolliency, and stability. Results indicated that all formulations exhibited shear-thinning behavior, with viscosity decreasing as shear rate increased. The pH values (4.30–6.15) were within the normal skin range, suggesting suitability for topical application. The creams demonstrated good spreadability (28–46 g·cm/s), were non-greasy, easily washable, and left no residue. All formulations were stable under accelerated conditions, with no phase separation or degradation observed. Notably, creams containing castor oil had higher viscosity compared to those formulated with arachis oil at equivalent concentrations. These findings demonstrate that locally sourced castor oil is a suitable pharmaceutical excipient for topical diclofenac sodium creams, offering desirable physicochemical properties and stability, and supporting its potential for commercial and therapeutic use in dermatological preparations.