II. Technological approaches to improve the dissolution behavior of nateglinide, a lipophilic insoluble drug: Co-milling

Effect of co-milling on dissolution rate of poorly soluble drugs

Co-milling of a drug with a co-former is an efficient technique to improve the solubility of drugs. Besides the particle size reduction, the co-milling process induces a structural disorder and the creation of amorphous regions. The extent of drug solubility enhancement is dependent on the proper choice of co-milling co-former. The aim of this work was to compare the effects of different co-formers (meglumine and polyvinylpyrrolidone) on the dissolution rates of glass forming (indomethacin) and non-glass forming (mefenamic acid) model drugs. A positive impact of the co-milling on the dissolution behavior was observed in all co-milled mixtures, even if no substantial amorphization was observed. While meglumine exhibited pronounced effects on the dissolution rate of both drugs, the slightest enhancement was observed in mixtures with polyvinylpyrrolidone. The evaluation of specific release rate revealed the surface activation of drug particle is responsible for improving the dissolution rate of both drug types, but for the glass former, this surface activation could be persistent while maintaining a high dissolution rate even until a high fraction of drug is released. Our results, therefore, indicate that adequate co-former choice and consideration of drug glass forming ability are important for a successful co-milling approach to poorly water-soluble drugs.

Effect of Solid Forms on Physicochemical Properties of Valnemulin

To improve the physicochemical properties of valnemulin (VLM), different solid forms formed by VLM and organic acids, including tartaric acid (TAR), fumaric acid (FUM), and oxalic acid (OXA), were successfully prepared and characterized by using differential scanning calorimetry (DSC), scanning electron microscope (SEM), X-ray powder diffraction (XRPD), and Fourier-transform infrared spectroscopy (FT-IR). The excess enthalpy Hex between VLM and other organic acids was calculated by COSMOthermX software and was used to evaluate the probability of forming multi-component solids between VLM and organic acids. By thermal analysis, it was confirmed that multi-component solid forms of VLM were thermodynamically more stable than VLM itself. Through dynamic vapor sorption (DVS) experiments, it was found that three multi-component solid forms of VLM had lower hygroscopicity than VLM itself. Furthermore, the intrinsic dissolution rate of VLM and its multi-component forms was determined in one kind of acidic aqueous medium by using UV-vis spectrometry. It was found that the three multi-component solid forms of VLM dissolved faster than VLM itself.

Development and Characterization of Microstructured, Spray-Dried Co-Amorphous Mixture of Antidiabetic Agents Stabilized by Silicate

In the present work, co-amorphous mixture (COAM) of poorly soluble nateglinide (NT) and highly soluble Metformin hydrochloride (MT) was prepared by spray drying method to improve the dissolution rate of NT and the processability of COAM. Binary spray-dried COAM of NT and MT (120 mg: 500 mg) was prepared in its clinical dose ratio whereas 20% Neusilin®US2 (NS) was added to prepare non-sticky, free flowing ternary COAM. Solubility studies of binary and ternary COAM exhibited sevenfold and tenfold rise in the solubility of NT. Complete amorphization of NT was revealed in XRPD and DSC studies of both COAM and hydrogen-bonding interactions were reflected in FTIR-spectra. SEM microphotographs illustrated round-shaped microparticles in ternary COAM against the irregular particles in binary COAM. In vitro dissolution of NT was significantly improved in ternary COAM > binary COAM > NT irrespective of dissolution medium. On contrary, MT has partially transformed to the amorphous form in COAM without altering the solubility. In accelerated stability studies, NT and MT devitrification was not observed in XRPD of ternary COAM in contrast to binary COAM. Therefore, enhanced dissolution of NT, stabilization of spray-dried dispersion, and its improved processability can be achieved by preparing ternary COAM of NT:MT:NS.

Selection of effective cocrystals former for dissolution rate improvement of active pharmaceutical ingredients based on lipoaffinity index

New theoretical screening procedure was proposed for appropriate selection of potential cocrystal formers possessing the ability of enhancing dissolution rates of drugs. The procedure relies on the training set comprising 102 positive and 17 negative cases of cocrystals found in the literature. Despite the fact that the only available data were of qualitative character, performed statistical analysis using binary classification allowed to formulate quantitative criterions. Among considered 3679 molecular descriptors the relative value of lipoaffinity index, expressed as the difference between values calculated for active compound and excipient, has been found as the most appropriate measure suited for discrimination of positive and negative cases. Assuming 5% precision, the applied classification criterion led to inclusion of 70% positive cases in the final prediction. Since lipoaffinity index is a molecular descriptor computed using only 2D information about a chemical structure, its estimation is straightforward and computationally inexpensive. The inclusion of an additional criterion quantifying the cocrystallization probability leads to the following conjunction criterions H_mix<-0.18 and ΔLA>3.61, allowing for identification of dissolution rate enhancers. The screening procedure was applied for finding the most promising coformers of such drugs as Iloperidone, Ritonavir, Carbamazepine and Enthenzamide.

Enhanced dissolution and bioavailability of Nateglinide by microenvironmental pH-regulated ternary solid dispersion: in-vitro and in-vivo evaluation

Objectives

Nateglinide, an Antidiabetic drug (BCS II), shows pH-dependent solubility and variable bioavailability. The purpose of study was to increase dissolution and bioavailability of Nateglinide by development of its microenvironmental pH-regulated ternary solid dispersion (MeSD).

Methods

MeSD formulation of Nateglinide, poloxamer-188 and Na2CO3 was prepared by melt dispersion in 1 : 2 : 0.2 w/w ratio and further characterised for solubility, In-vitro dissolution, microenvironmental pH, crystallinity/amorphism, physicochemical interactions, bioavailability in Wistar rats.

Key findings

Solubility of Nateglinide was increased notably in MeSD, and its in-vitro dissolution study showed fourfold increase in the dissolution, particularly in 1.2 pH buffer. Prominent reduction in the peak intensity of X-ray powder diffraction (XRPD) and absence of endotherm in DSC thermogram confirmed the amorphism of Nateglinide in MeSD. Attenuated total reflectance Fourier transform infrared spectra revealed the hydrogen bond interactions between Nateglinide and poloxamer-188. In-vivo study indicated that MeSD exhibited fourfold increase in area under curve over Nateglinide. Tmax of MeSD was observed at 0.25 h, which is beneficial for efficient management of postprandial sugar. Instead of mere transformation of the Nateglinide to its amorphous form as evidenced by DSC and XRPD, formation of a soluble carboxylate compound of Nateglinide in MeSD was predominantly responsible for dissolution and bioavailability enhancement.

Conclusions

The study demonstrates the utility of MeSD in achieving pH-independent dissolution, reduced Tmax and enhanced bioavailability of Nateglinide.

Polymer co-processing of ibuprofen through compaction for improved oral absorption

Improving oral absorption remains a major challenge for the biopharmaceutical industries aiming at introducing newer drugs or prolonging product life cycle.