Simultaneous improvement of physical stability, dissolution, bioavailability, and antithrombus efficacy of Aspirin and Ligustrazine through cocrystallization

New Cocrystals of Ligustrazine: Enhancing Hygroscopicity and Stability

Ligustrazine (TMP) is the main active ingredient extracted from Rhizoma Chuanxiong, which is used in the treatment of cardiovascular and cerebrovascular diseases, with the drawback of being unstable and readily sublimated. Cocrystal technology is an effective method to improve the stability of TMP. Three benzoic acid compounds including P-aminobenzoic acid (PABA), 3-Aminobenzoic acid (MABA), and 3,5-Dinitrobenzoic acid (DNBA) were chosen for co-crystallization with TMP. Three novel cocrystals were obtained, including TMP-PABA (1:2), TMP-MABA (1.5:1), and TMP-DNBA (0.5:1). Hygroscopicity was characterized by the dynamic vapor sorption (DVS) method. Three cocrystals significantly improved the hygroscopicity stability, and the mass change in TMP decreased from 25% to 1.64% (TMP-PABA), 0.12% (TMP-MABA), and 0.03% (TMP-DNBA) at 90% relative humidity. The melting points of the three cocrystals were all higher than TMP, among which the TMP-DNBA cocrystal had the highest melting point and showed the best stability in reducing hygroscopicity. Crystal structure analysis shows that the mesh-like structure formed by the O-H⋯N hydrogen bond in the TMP-DNBA cocrystal was the reason for improving the stability of TMP.

Development of direct compression Acetazolamide tablet with improved bioavailability in healthy human volunteers enabled by cocrystallization with p-Aminobenzoic acid

Pharmaceutical cocrystallization has been widely used to improve physicochemical properties of APIs. However, developing cocrystal formulation with proven clinical success remains scarce. Successful translation of a cocrystal to suitable dosage forms requires simultaneously improvement of several deficient physicochemical properties over the parent API, without deteriorating other properties critical for successful product development. In the present work, we report the successful development of a direct compression tablet product of acetazolamide (ACZ), using a 1:1 cocrystal of acetazolamide with p-aminobenzoic acid (ACZ-PABA). The ACZ-PABA tablet exhibits superior biopharmaceutical performance against the commercial tablet, DIAMOX® (250 mg), in healthy human volunteers, leading to more than 50 % reduction in the required dose.

Tetramethylpyrazine-loaded liposomes surrounded by hydrogel based on sodium alginate and chitosan as a multifunctional drug delivery System for treatment of atopic dermatitis

Tetramethylpyrazine (TMP) has low bioavailability due to its fast metabolism and short half-life, which is not conducive to transdermal treatment of atopic dermatitis (AD). Therefore, in this study, TMP was encapsulated into liposomes (Lip) by film dispersion method, and then the surface of Lip was modified by sodium alginate (ALG) and chitosan (CS). The tetramethylpyrazine-loaded liposomes in sodium alginate chitosan hydrogel called T-Lip-AC hydrogel. In vitro experiments, we found that T-Lip-AC hydrogel not only had the antibacterial effect of CS, but also enhanced the anti-inflammatory and antioxidant effects of TMP. In addition, T-Lip-AC hydrogel could also provide a moist healing environment for AD dry skin and produce better skin permeability, and can also achieve sustained drug release, which is conducive to the treatment of AD. The lesions induced by 1-chloro-2,4-dinitrobenzene were used as the AD lesions model to test the therapeutic effect of the T-Lip-AC hydrogel on AD in vivo. The studies have showed that T-Lip-AC hydrogel could effectively promote wound healing. Therefore, we have developed a T-Lip-AC hydrogel as multifunctional hydrogel drug delivery system, which could become an effective, safe and novel alternative treatment method for treating AD.

Tuning Caco-2 permeability by cocrystallization: Insights from molecular dynamics simulation

Emerging evidence suggests that intestinal permeability can be potentially enhanced through cocrystallization. However, a mechanism for this effect remains to be established. In this study, we first demonstrate the enhancement in intestinal permeability, evaluated by the Caco-2 cell permeability assay, of acetazolamide (ACZ) in the presence of a conformer, p-aminobenzoic acid (PABA), delivered in the form of a 1:1 cocrystal. The binding strength of ACZ and PABA with the Pgp efflux transporter, either alone or as a mixture, was calculated using molecular dynamics simulation. Results show that PABA weakens the binding of ACZ with Pgp, which leads to a lower efflux ratio and elevated permeability of ACZ. This work provides molecular-level insights into a potentially effective strategy to improve the intestinal permeability of drugs. If the same cocrystal also exhibits higher solubility, oral bioavailability of BCS IV drugs can likely be improved by forming a cocrystal with a Pgp inhibitor.

Aspirin microcrystals deposited on high-density microneedle tips for the preparation of soluble polymer microneedles

To reduce mucosal damage in the gastrointestinal tract caused by aspirin, aspirin microcrystals were loaded in soluble polymeric microneedle (MN) tips. Aspirin was prepared into aspirin microcrystals by jet milling. Aspirin microcrystals with particle sizes of 0.5-5 μm were loaded on MN tips with a height of 250 µm or 300 µm. The aspirin microcrystals suspended in a polymer solution were concentrated in the MN tips under negative pressure. The aspirin microcrystals had high stability in the MNs since they were not dissolved in solution during the fabrication process. The MN patch packaged in an aluminum-plastic bag containing silica gel desiccant can be stored at 4 °C. The MN tips implanted in the skin of Institute of Cancer Research (ICR) mice dissolved within 30 min. Isolated porcine ear skin was punctured by MNs with heights of 300 μm and 250 μm to depths of 130 μm and 90 μm, respectively. The fluorescent red (FR) release from MNs reached 98.59% within 24 h. The MNs delivered aspirin microcrystals to the epidermis and dermis, providing a smooth plasma concentration in rats. The MNs loaded with aspirin microcrystals did not evoke primary irritation on the dorsal skin of Japanese white rabbits. In summary, MNs loaded with aspirin microcrystals provide a new approach to improve the stability of aspirin in MN patches.

Particle preparation of pharmaceutical compounds using supercritical antisolvent process: current status and future perspectives

The low aqueous solubility and subsequently slow dissolution rate, as well as the poor bioavailability of several active pharmaceutical ingredients (APIs), are major challenges in the pharmaceutical industry. In this review, the particle engineering approaches using supercritical carbon dioxide (SC CO₂) as an antisolvent are critically reviewed. The different SC CO₂-based antisolvent processes, such as the gas antisolvent process (GAS), supercritical antisolvent process (SAS), and a solution-enhanced dispersion system (SEDS), are described. The effect of process parameters such as temperature, pressure, solute concentration, nozzle diameter, SC CO₂ flow rate, solvent type, and solution flow rate on the average particle size, particle size distribution, and particle morphology is discussed from the fundamental perspective of the SAS process. The applications of the SAS process in different formulation approaches such as solid dispersion, polymorphs, cocrystallization, inclusion complexation, and encapsulation to enhance the dissolution rate, solubility, and bioavailability are critically reviewed. This review highlights some areas where the SAS process has not been adequately explored yet. This review will be helpful to researchers working in this area or planning to explore SAS process to particle engineering approaches to tackle the challenge of low solubility and subsequently slow dissolution rate and poor bioavailability.

Inhibiting Sublimation of Thymol by Cocrystallization

A thymol:4,4'-dipyridyl (2:1) cocrystal (Form I) is reported to suppress thymol sublimation. The cocrystal was prepared via solution-mediated phase transformation and its structure is sustained by O-H (phenol) ··· N (pyridyl) hydrogen bonds between two individual components. A cocrystal polymorph (Form II) was formed via solid state transformation or via vapor phase upon heating. Using gravimetry analysis, it was demonstrated that cocrystal Form I decreased the sublimation rate of thymol by 38-fold. This study demonstrates that cocrystallization is an effective approach to reduce vapor pressure and sublimation of solids, thus achieving odor-masking.