Indomethacin-omeprazole as therapeutic hybrids? Salt and co-amorphous systems enhancing physicochemical and pharmacological properties

Multidrug therapeutic hybrids constitute a promising proposal to overcome problems associated with traditional formulations containing physical mixtures of drugs, potentially improving pharmacological and pharmaceutical performance. Indomethacin (IND) is a non-selective non-steroidal anti-inflammatory drug (NSAIDs) that acts by inhibiting normal processes of homeostasis, causing a series of side effects, such as gastrointestinal symptoms. Proton pump inhibitors, such as omeprazole (OME), have been used to treat such gastrointestinal tract symptoms. In this work, two new multidrug therapeutic hybrids were prepared (an IND:OME salt and an IND:OME co-amorphous system) by ball mill grinding crystalline IND and OME under different conditions, i.e., liquid assisted grinding (LAG) with ethanol and dry grinding, respectively. The crystalline salt returned to a neutral state co-amorphous system when submitted to ball mill grinding in the absence of solvent (dry grinding), but the reverse process (LAG of the IND:OME co-amorphous system) showed partial decomposition of OME. The IND:OME co-amorphous system showed a higher physical stability than the neat IND and OME amorphous materials (with an amorphous stability longer than 100 days, compared to 4 and 16 h for the neat amorphous drugs, respectively, when stored at dry conditions at room temperature). Furthermore, OME presented a higher chemical stability in solution when dissolved from a salt form than from the pure crystalline form. The dissolution studies showed a dissolution enhancement for IND in both salt (1.8-fold after 8 h of dissolution) and co-amorphous (2.5-fold after 8 h of dissolution) forms. Anti-inflammatory activity using a mice paw oedema model showed an increase of the pharmacological response to IND at a lower dose (∼5mg/kg) for both IND:OME salt (2.8-fold) and IND:OME co-amorphous system (3.2-fold) after 6 h, when compared to the positive control group (IND, administered at 10 mg/kg). Additionally, the anti-inflammatory activity of both salt and co-amorphous form was faster than for the crystalline IND. Finally, an indomethacin-induced gastric ulceration assay in mice resulted in a higher mucosal protection at the same dose (40 mg/kg) for both IND:OME salt and IND:OME co-amorphous system when compared with crystalline OME.

Preparation and Characterization of a Rifampicin Coamorphous Material with Tromethamine Coformer: An Experimental-Theoretical Study

Rifampicin (RIF) is an antibiotic used to treat tuberculosis and leprosy. Even though RIF is a market-available drug, it has a low aqueous solubility, hindering its bioavailability. Among the strategies for bioavailability improvement of poorly soluble drugs, coamorphous systems have been revealed as an alternative in the increase of the aqueous solubility of drug systems and at the same time also increasing the amorphous state stability and dissolution rate when compared with the neat drug. In this work, a new coamorphous form from RIF and tromethamine (TRIS) was synthesized by slow evaporation. Structural, electronic, and thermodynamic properties and solvation effects, as well as drug-coformer intermolecular interactions, were studied through density functional theory (DFT) calculations. Powder X-ray diffraction (PXRD) data allowed us to verify the formation of a new coamorphous. In addition, the DFT study indicates a possible intermolecular interaction by hydrogen bonds between the available amino and carbonyl groups of RIF and the hydroxyl and amino groups of TRIS. The theoretical spectra obtained are in good agreement with the experimental data, suggesting the main interactions occurring in the formation of the coamorphous system. PXRD was used to study the physical stability of the coamorphous system under accelerated ICH conditions (40 °C and 75% RH), indicating that the material remained in an amorphous state up to 180 days. The thermogravimetry result of this material showed a good thermal stability up to 153 °C, and differential scanning calorimetry showed that the glass temperature (Tg) was at 70.0 °C. Solubility studies demonstrated an increase in the solubility of RIF by 5.5-fold when compared with its crystalline counterpart. Therefore, this new material presents critical parameters that can be considered in the development of new coamorphous formulations.

Recent advances in dual-drug co-amorphous systems

Poor solubility of drugs and therapeutic candidates poses a significant challenge in drug research and development. Biopharmaceutical class II drugs exhibit limited absorption because of their weak solubility and high permeability. Co-amorphous systems (CAMs) have been studied widely as a way to improve the solubility of drugs. This review summarizes recent advancements in dual-drug CAMs, including improvements in formulation, manufacturing, and solid-state characterization, and highlights the importance of enhancing solubility and stability. It emphasizes the potential synergistic effects of two drugs in CAMs and explores formulation strategies and challenges related to maintaining the amorphous state. Case studies demonstrate the successful application of CAMs in combination therapies that offer improved therapeutic efficacy.

Co-amorphous systems consisting of indomethacin and the chiral co-former tryptophan: Solid-state properties and molecular mobilities

In this study the influence of an enantiomeric co-former and the preparation method on the solid-state properties and physical stability of co-amorphous systems were investigated. Co-amorphous systems consisting of indomethacin (IND) and chiral tryptophan (TRP) as co-former in its two enantiomeric forms, as racemate, and as conglomerate (equimolar mixture of D- and L-TRP) were prepared. Co-amorphization was achieved by ball milling (BM) and spray drying (SD). The effects of chirality and preparation method on the solid-state properties and physical stabilities of the systems were investigated by XRPD, FTIR and mDSC. Differences in the BM process were caused by the enantiomeric properties of the co-former: The IND/TRP conglomerate (IND/TRPc) turned co-amorphous after 60 min. In contrast, co-amorphization of IND/L-TRP and IND/D-TRP required 80 min of ball milling, respectively, and the co-amorphous IND/TRP racemate (IND/TRPr) was obtained only after 90 min of ball milling. Although the intermolecular interactions of the co-amorphous systems prepared by BM and SD were similar (determined by FTIR), the T_g values differed (∼87 °C for the ball milled and ∼62 °C for the spray dried systems). The physical stabilities of the ball milled co-amorphous systems varied between 3 and 11 months if stored at elevated temperature and dry conditions, with the highest stability for the IND/TRPc system and the lowest stability for the IND/TRPr system, and these differences correlated with the calculated relaxation times. In contrast, all spray dried systems were stable only for 1 month and their relaxation times were similar. It could be shown that the chirality of a co-former and the preparation method influence the solid-state properties, thermal properties and physical stability of IND/TRP systems.

Development of Co-Amorphous Loratadine–Citric Acid Orodispersible Drug Formulations

This study aimed at the preparation and characterization of co-amorphous loratadine–citric acid orally disintegrating dosage forms (ODx). A co-amorphous loratadine–citric acid was prepared by solvent evaporation method in three different molecular ratios. DSC, FTIR, and dissolution studies have been conducted for the binary system. The co-amorphous system was used to obtain oral lyophilizates and orally disintegrating tablets by direct compression. Diameter, thickness, hardness, disintegration time, uniformity of mass, and dissolution was determined for the dosage forms. DSC curves showed a lack of sharp endothermic peaks for the binary systems. FTIR spectra presented a hypsochromic modification of the characteristic peaks. Dissolution studies indicated a five-fold increase in the dissolved amount compared to pure loratadine in water. Disintegration times of direct compression ODx varied in the range of 34–41 s and for freeze-dried ODx in the range of 8–9 s. Friability was under 1% in all cases. The dissolution of loratadine in buffer solution at pH = 1 was almost complete. In conclusion binary systems of loratadine and citric acid enhance solubility and combined with the orally disintegrating pharmaceutical form also increase patient compliance.

(Co-)amorphization of enantiomers - Investigation of the amorphization process, the physical stability and the dissolution behavior

A novel approach for improvement of the aqueous solubility of poorly water soluble compounds applying co-amorphous systems was investigated by application of the enantiomers of the chiral amino acid tryptophan (TRP) as the model system. (Co-)amorphization of various forms of crystalline TRP was achieved by ball milling. Solid state analysis demonstrated significant differences in the amorphization tendency and physical stability between the two TRP enantiomers alone, the TRP racemate and an equimolar physical mixture of D- and L-TRP (TRP conglomerate). Ball milling for 6 h was required to obtain fully amorphous plain D- and L-TRP, whereas the TRP racemate and the TRP conglomerate were transformed into their amorphous forms already within 90 and 60 min of ball milling, respectively. Physical stability of the co-amorphous TRP conglomerate was observed for up to 60 d at ambient conditions as well as 40 °C/0 % RH. In contrast, the amorphous TRP racemate showed a reduced physical stability under ambient conditions. Interestingly, the intrinsic dissolution rates of the amorphous TRP conglomerate and racemate were not higher than those of the respective crystalline forms. In conclusion, applying two enantiomers of a chiral compound may be a promising approach for fast amorphization of an API and for improving the physical stability of the resulting amorphous form.

Amorphous Salts Solid Dispersions of Celecoxib: Enhanced Biopharmaceutical Performance and Physical Stability

Numerous amorphous solid dispersion (ASD) formulations of celecoxib (CEL) have been attempted for enhancing the solubility, dissolution rate, and in vivo pharmacokinetics via high drug loading, polymer combination, or by surfactant addition. However, physical stability for long-term shelf life and desired in vivo pharmacokinetics remains elusive. Therefore, newer formulation strategies are always warranted to address poor aqueous solubility and oral bioavailability with extended shelf life. The present investigation elaborates a combined strategy of amorphization and salt formation for CEL, providing the benefits of enhanced solubility, dissolution rate, in vivo pharmacokinetics, and physical stability. We generated amorphous salts solid dispersion (ASSD) formulations of CEL via an in situ acid-base reaction involving counterions (Na⁺ and K⁺) and a polymer (Soluplus) using the spray-drying technique. The generated CEL-Na and CEL-K salts were homogeneously and molecularly dispersed in the matrix of Soluplus polymer. The characterization of generated ASSDs by differential scanning calorimetry revealed a much higher glass-transition temperature (T_g) than the pure amorphous CEL, confirming the salt formation of CEL in solid dispersions. The micro-Raman and proton nuclear magnetic resonance spectroscopy further confirmed the formation of salt at the -S═O position in the CEL molecules. CEL-Na-Soluplus ASSD exhibited a synergistic enhancement in the aqueous solubility (332.82-fold) and in vivo pharmacokinetics (9.83-fold enhancement in the blood plasma concentration) than the crystalline CEL. Furthermore, ASSD formulations were physically stable for nearly 1 year (352 days) in long-term stability studies at ambient conditions. Hence, we concluded that the ASSD is a promising strategy for CEL in improving the physicochemical properties and biopharmaceutical performance.