Diclofenac Potassium and Isonicotinamide Cocrystals for Enhanced Solubility: In Vitro Evaluation of Hard Gelatin Capsules

Abstract

Diclofenac potassium (DIC-K), classified as a Biopharmaceutics Classification System (BCS) Class II drug, exhibits low solubility and high permeability. It is a widely used non-steroidal anti-inflammatory drug (NSAID) with anti-inflammatory, antipyretic, and analgesic effects. This study aimed to enhance the solubility of DIC-K by preparing cocrystals with isonicotinamide (INA) as a coformer and to evaluate their in vitro performance. The prepared DIC-K+INA cocrystals were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Solubility studies were conducted for pure DIC-K and DIC-K+INA cocrystals in different media (0.1 N HCl, pH 1.2; phosphate buffer (PB), pH 4.5; and PB, pH 6.8). Hard gelatin capsules containing either pure DIC-K or DIC-K+INA cocrystals were formulated using the dry granulation method, and their dissolution profiles were evaluated in PB (pH 6.8). At 15 min, the amount of DIC-K dissolved from the pure DIC-K capsules was 72%, whereas that from the DIC-K+INA cocrystal capsules reached 92%. PXRD, FTIR, and DSC analyses supported the formation of a new crystalline phase, indicating successful cocrystal formation between DIC-K and INA. Overall, DIC-K+INA cocrystals enhanced the solubility and dissolution performance of DIC-K, demonstrating the potential of cocrystallization as a formulation strategy for poorly soluble drugs.

Keywords

• Diclofenac potassium
• Isonicotinamide
• Cocrystal
• Solubility enhancement
• Capsule

Project Number

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Ethical Statement

Ethics committee approval was not required for this study because of there was no study on animals or humans.

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