Overview of Extensively Employed Polymeric Carriers in Solid Dispersion Technology

Solid dispersion is the preferred technology to prepare efficacious forms of BCS class-II/IV APIs. To prepare solid dispersions, there exist a wide variety of polymeric carriers with interesting physicochemical and thermochemical characteristics available at the disposal of a formulation scientist. Since the advent of the solid dispersion technology in the early 1960s, there have been more than 5000 scientific papers published in the subject area. This review discusses the polymeric carrier properties of most extensively used polymers PVP, Copovidone, PEG, HPMC, HPMCAS, and Soluplus® in the solid dispersion technology. The literature trends about preparation techniques, dissolution, and stability improvement are analyzed from the Scopus® database to enable a formulator to make an informed choice of polymeric carrier. The stability and extent of dissolution improvement are largely dependent upon the type of polymeric carrier employed to formulate solid dispersions. With the increasing acceptance of transfer dissolution setup in the research community, it is required to evaluate the crystallization/precipitation inhibition potential of polymers under dynamic pH shift conditions. Further, there is a need to develop a regulatory framework which provides definition and complete classification along with necessarily recommended studies to characterize and evaluate solid dispersions.

In vitro and in vivo comparison between crystalline and co-amorphous salts of naproxen-arginine

Liquid-assisted grinding (LAG) and dry ball milling (DBM) have recently been used to obtain different physical forms of drug-amino acid salts with promising dissolution and physical stability properties. In this work, crystalline and co-amorphous naproxen-arginine mixtures were prepared using LAG and DBM, respectively, and compared with regard to their in vitro and in vivo performance. X-ray powder diffraction and Fourier-transformed infrared spectroscopy showed that LAG led to the formation of a crystalline salt, while DBM led to a co-amorphous salt. These results agreed with the differential scanning calorimetry profiles: a melting point of 230 °C was determined for the crystalline salt, while the co-amorphous formulation showed a single glass transition temperature at approx. 92 °C. Both solid state forms of the salt showed increased intrinsic dissolution rates (14.8 and 74.1-fold, respectively) and also higher solubility (25.3 and 29.8-fold, respectively) compared to the pure crystalline drug in vitro. Subsequently, the co-amorphous salt revealed an improved bioavailability in a pharmacokinetic study, showing a 1.5-fold increase in AUC_0-t and a 2.15-fold increase in c_max compared to the pure crystalline drug. In contrast, even though showing a better in vitro performance, the crystalline salt interestingly did not show an increase in bioavailability in comparison to pure crystalline naproxen.

Considerations for the selection of co-formers in the preparation of co-amorphous formulations

Co-amorphous drug delivery systems are evolving as a credible alternative to amorphous solid dispersions technology. In Co-amorphous systems (CAMs), a drug is stabilized in amorphous form using small molecular weight compounds called as co-formers. A wide variety of small molecular weight co-formers have been leveraged in the preparation of CAMs. The stability and supersaturation potential of prepared co-amorphous phases largely depend on the type of co-former employed in the CAMs. However, the rationality behind the co-former selection in co-amorphous systems is poorly understood and scarcely compiled in the literature. There are various facets to the rational selection of co-former for CAMs. In this context, the present review compiles various factors affecting the co-former selection. The factors have been broadly classified under Thermodynamic, Kinetic and Pharmacokinetic-Pharmacologically relevant parameters. In particular, the importance of Glass transition, Miscibility, Liquid-Liquid phase separation (LLPS), Crystallization inhibition has been deliberated in detail.

The relevance of co-amorphous formulations to develop supersaturated dosage forms: In-vitro, and ex-vivo investigation of Ritonavir-Lopinavir co-amorphous materials

Ritonavir and Lopinavir have previously been demonstrated to decrease the maximum solubility advantage and flux in the presence of each other. The present study investigated the ability of Ritonavir and Lopinavir co-amorphous materials to generate a supersaturated state. Further, it explored the precipitation and flux behavior of co-amorphous materials. The co-amorphous materials of Ritonavir and Lopinavir were prepared by quench cool method and characterized in the solid state using XRPD, DSC, FTIR. The solubility studies were conducted in USP phosphate buffer (pH 6.8) for 12 h. The supersaturation potential and precipitation behavior were studied employing pH shift method. Further, the diffusion behavior was explored in vitro and ex-vivo using a semipermeable membrane and intestinal everted sac method, respectively. The results showed that the co-amorphous materials have the potential to generate a supersaturated state. However, the reduction in the amorphous solubility was observed for both the drug(s) and the degree of reduction was found proportionate with the mole fraction of the compound in the co-amorphous material. Interestingly, the flux of both the drugs from co-amorphous material of 2:1 M ratio (Ritonavir 2: Lopinavir 1) was found exceeding the flux of the individual drugs in the amorphous form. The significant increase in the flux was attributed to the improved drug release properties due to precipitation of drug rich phase of nano/micro dimensions.

Osmotically controlled pulsatile release capsule of montelukast sodium for chronotherapy: statistical optimization, in vitro and in vivo evaluation

The purpose of present study was to design, optimize and evaluate osmotically controlled pulsatile release capsule (PRC) of montelukast sodium (MKS) for the prevention of episodic attack of asthma in early morning and associated allergic rhinitis. Assembly of the capsular systems consisted of push, active and plug tablet arranged from bottom to top in hard gelatin capsule. The capsule system was coated with a semi-permeable membrane of cellulose acetate and drilled towards plug side in cap. A three-factor, three-level central composite design (CCD) with α = 1 was introduced to execute the experiments and quadratic polynomial model was generated to predict and assess the independent variables with respect to the dependent variables. The composition of optimal formulation was determined as weight of push tablet 138 mg (coded value: +0.59), plug tablet 60 mg (coded value: +0.49) and coating weight gain of 8.4 mg (coded value: -0.82). The results showed that the optimal formulation of PRCs had lag time of 4.5 h, release at 6 and 12 h are 61.95% and 96.29%, respectively. The X-ray radiographic imaging study was carried out to monitor the in vivo behavior of developed barium sulfate-loaded PRCs in rabbits under fasting conditions. In vivo pharmacokinetic study revealed Tmax of 2 h for marketed tablets; however 7 h for PRCs with initial lag time of 4 h. Thus designed capsular system may be helpful for patients with episodic attack of asthma in early morning and associated allergic rhinitis.

The Significance of Utilizing In Vitro Transfer Model and Media Selection to Study the Dissolution Performance of Weak Ionizable Bases: Investigation Using Saquinavir as a Model Drug

This study investigated the dissolution behavior of BCS class II ionizable weak base Saquinavir and its mesylate salt in the multi-compartment transfer setup employing different composition of dissolution media. The dissolution behavior of Saquinavir was studied by using a two-compartment transfer model representing the transfer of drug from the stomach (donor compartment) to the upper intestine (acceptor compartment). Various buffers like phosphate, bicarbonate, FaSSIF, and FeSSIF were employed. The dissolution was also studied in the concomitant presence of the additional solute, i.e., Quercetin. Further, the dissolution profiles of Saquinavir and its mesylate salt were simulated by GastroPlus^TM, and the simulated dissolution profiles were compared against the experimental ones. The formation of in situ HCl salt and water-soluble amorphous phosphate aggregates was confirmed in the donor and acceptor compartments of the transfer setup, respectively. As the consequence of the lower solubility product of HCl salt of Saquinavir, the solubility advantage of mesylate salt was vanished leading to the lower than the predicted dissolution in the acceptor compartment. However, the formation of water-soluble aggregates in the presence of the phosphate salts was observed leading to the higher than the predicted dissolution of the free base in the transfer setup. Interestingly, the formation of such water-soluble aggregates was found to be hindered in the concomitant presence of an ionic solute resulting in the lower dissolution rates. The in situ generation of salts and aggregates in the transfer model lead to the inconsistent prediction of dissolution profiles by GastroPlus^TM.

Development and validation of RP-HPLC method with ultraviolet detection for estimation of montelukast in rabbit plasma: Application to preclinical pharmacokinetics

OBJECTIVE

To develop a liquid-liquid extraction based reverse phase liquid chromatography method for estimation of montelukast in rabbit plasma.

METHODS

Chromatographic separation was carried out using Phenomenex Luna C18 column (250 mm × 4.6 mm × 5 μm) with mobile phase composed of ammonium acetate buffer (20 Mm), pH 5.5 and acetonitrile in 20:80, v/v ratio. The analyte was monitored with UV detector at 345 nm. The developed method was validated with respect to linearity, accuracy, precision, specificity and stability.

RESULTS

The peak area ratio of montelukast (MKS) to that of internal standard was used for the quantification of samples. Calibration curves were linear in the concentration range of 20-2000 ng mL(-1). The LOD and LLOQ of present method were found out to be 10 ng mL(-1) and 20 ng mL(-1) respectively. The intra-day and inter-day %CV values for MKS were below 6.06% and 8.43%. Intra-day and inter-day accuracies were within 95.81% and 110.90%, respectively. Extraction recoveries of drug from rabbit plasma were >66.47%.

CONCLUSION

A simple, alternative, reproducible and sensitive HPLC-UV method was developed for MKS that can be used in preclinical pharmacokinetics.

Dronedarone HCl-Quercetin Co-Amorphous System: Characterization and RP-HPLC Method Development for Simultaneous Estimation

BACKGROUND

Dronedarone HCl (DRN) is an anti-arrhythmic drug indicated for atrial fibrillation. DRN has a low solubility of 2 µg/mL and 4% bioavailability, thus it is formulated as a co-amorphous system to enhance its solubility by using quercetin (QCT) as a co-former. A sensitive, accurate, and economic method for the simultaneous quantification of DRN and QCT in formulation is not found in the literature.

OBJECTIVE

To develop a Reverse Phase -HPLC method for the simultaneous estimation of DRN and QCT in a DRN-QCT co-amorphous system.

METHOD

The co-amorphous system was prepared using a solvent evaporation technique with DRN and QCT in a 1:1 molar ratio. The separation was achieved on a Purospher® STAR C18 (250 mm × 4.6 mm × 5 μm id (internal diameter)) column with the mobile phase comprising of acetonitrile and a 25 mM phosphate buffer pH 3.6 (60:40%, v/v).

RESULTS

DRN and QCT were retained on the column for 6.7 and 3.5 min, respectively. For both molecules, the method was developed with a wide linearity range of 0.2-500 µg/mL. The LOD for DRN was found to be 0.0013 µg/mL and for QCT it was found to be 0.0026 µg/mL. The LOQ for DRN was found to be 0.0041 µg/mL, and for QCT it was 0.0078 µg/mL.

CONCLUSIONS

The method was validated as per International Conference on Harmonization (ICH) guidelines for linearity, precision, accuracy, and robustness. The method was used in simultaneous quantification of DRN and QCT in co-amorphous samples.

HIGHLIGHTS

The method developed was used for the analysis of content uniformity and solubility samples of co-amorphous system, where the method was able to successfully quantify DRN and QCT. Low detection and quantification limits contribute to the sensitivity of the method and wide linearity range assures the robust and precise quantification of molecules.

Bioavailability Enhancement of Rizatriptan Benzoate by Oral Disintegrating Strip: In vitro and In vivo Evaluation

Oral disintegrating strips containing rizatriptan benzoate, a selective 5-hydroxy tryptamine receptor agonist with anti migraine property, was developed using polyvinyl alcohol, sodium alginate and hydroxyl propyl methylcellulose as the base materials. The analytical and bioanalytical methods were developed and validated using HPLC (PDA and flouroscence detectors). The dissolution study performed on the strips revealed that all the five formulations, release the drug within eight minutes. Under ICH accelerated stability conditions, strips were stable at 40°C and 75% humidity for eight weeks. Furthermore, pharmacokinetic properties of oral strip were compared with rizatriptan benzoate marketed tablet. Oral disintegrating strip and tablet showed significantly higher bioavailability. Oral strip exhibited better pharmacokinetic parameters than rizatriptan marketed tablet. The Tmax, Cmax, AUC and t1/2 for oral strip were found to be 1.00 h, 64.13±19.46 ng/mL, 352.00±71.57 ng/mL/h and 3.09±1.03 h respectively, whereas, tablet showed 1.5 h, 38.00±13.43 ng/mL, 210.38± 40.37ng/mL/h and 1.66±0.31 h respectively. These findings confirm that the rizatriptan benzoate oral disintegrating strip is potentially a useful tool for an effective treatment of migraine with improved bioavailability, rapid onset of action and with increased patient compliance.

A computational-based approach to fabricate Ceritinib co-amorphous system using a novel co-former Rutin for bioavailability enhancement

In this study, we used molecular simulations to design Ceritinib (CRT) co-amorphous materials (CAMs) with concurrent improvement in solubility and bioavailability. Computational modeling enabled us to select the co-former by estimating the binding energy and intermolecular interactions. Rutin (RTH) was selected as a co-former for CRT CAMs using the solvent evaporation method to anticipate simultaneous improvement of solubility and bioavailability. The solid state characterization using DSC, XRPD, FT-IR, and a significant shift in Gordon Taylor experimental Tg values of co-amorphous materials revealed single amorphous phase formation and intermolecular interactions between CRT and RTH. The co-amorphous materials exhibited physical stability for up to 4 months under dry conditions (40 °C). Further, co-amorphous materials maintained the supersaturation for 24 hrs and improved solubility as well as dissolution of CRT. CRT:RTH 1:1 CAMs improved the permeability of CRT by 2 fold, estimated by employing the everted gut sac method. The solubility advantage of CAMs was also reflected in pharmacokinetic parameters, with a 3.1-fold and 2-fold improvement of CRT:RTH 2:1 in CRT exposure (AUC 0-t) and plasma concentration (Cmax) compared to the physical mixture, respectively.

Implications of phase solubility/miscibility and drug-rich phase formation on the performance of co-amorphous materials: The case of Darunavir co-amorphous materials with Ritonavir and Indomethacin as co-formers

The present study was designed to investigate the contribution of solid-state and the impact of composite drug-rich phase generated as a consequence of pH shift on the maximum achievable supersaturation of co-amorphous formulations. The co-amorphous phases of weak base-weak base-pair i.e. Ritonavir and Darunavir were prepared in anticipation of studying the effect of drug-rich phase consequent to pH shift. While the co-amorphous phases of weak base-Weak acid pair i.e. Darunavir and Indomethacin were studied to understand the manifestation of the solid-state drug: co-former miscibility in the absence of drug rich phase. Thermodynamically, the lowering of the supersaturation was found commensurate with the mole fraction of the respective component (Drug/Co-former) within the co-amorphous materials for both Darunavir: Ritonavir and Darunavir: Indomethacin pair. Kinetically, for Darunavir: Ritonavir co-amorphous materials, the shift in the pH from acidic to the neutral side led to the generation of drug-rich phase and subsequent LLPS. The free drug concentration achieved in the bulk of the solution was found dependent upon the mole fraction of the respective component within the drug-rich phase. The relative mole fraction of each component within the composite drug-rich phase is dictated by pH-dependent solubility and molecular weight of the individual components.

In vitro, in-vivo, and in-silico investigation of physicochemical interactions between pioglitazone and rifampicin

There is a possibility of in-situ physicochemical interactions between concomitantly administered drugs. This study aimed to investigate such physicochemical interactions between pioglitazone and rifampicin. Pioglitazone exhibited significantly higher dissolution in the presence of rifampicin, while the dissolution of rifampicin remained unaffected. The solid-state characterization of precipitates recovered after pH-shift dissolution experiments revealed the conversion of pioglitazone into an amorphous form in the presence of rifampicin. The Density Function Theory (DFT) calculations showed the intermolecular hydrogen bonding between rifampicin and pioglitazone. In-situ conversion of pioglitazone in amorphous form and subsequent supersaturation of GIT milieu translated into significantly higher in-vivo exposure of pioglitazone and its metabolites (M-III and M-IV) in Wistar rats. Therefore, it is advisable to consider the possibility of physicochemical interactions between concomitantly administered drugs. Our findings may be beneficial in tailoring the dose of concomitantly administered drugs, particularly for chronic conditions that entail polypharmacy.

Development and validation of reversed-phase high-performance liquid chromatography method for estimation of rizatriptan benzoate in oral strip formulations

Aim:

A simple, accurate, precise, and reproducible reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for the determination of rizatriptan benzoate in oral strip formulations.

Methodology:

Separation was achieved under optimized chromatographic condition on a Hiper C₁₈ column (250 mm × 4.6 mm, 5 m) using Shimadzu HPLC. The mobile phase consisted of phosphate buffer (20 mM pH adjusted to 3.2 ± 0.005 with ortho phosphoric acid): Methanol in the ratio of 70:30 v/v with isocratic elution at a flow rate of 1 ml/min at ambient temperature was performed. The detection was carried out at 225 nm using photodiode array detector. The method was validated as per Q1A (R2) guidelines and suitability of developed method was ascertained by using optimized oral strip formulation.

Results:

The retention time of rizatriptan benzoate was found to be 5.17 min, and the calibration curve was linear in the concentration range of 0.20-20 mg/mL (r²= 0.9998). The limit of detection and the limit of quantitation were found to be 0.016 mg/mL and 0.0528 mg/mL, respectively. Method validation parameters were found to be within the specified limits. The percentage drug content of oral strips formulation was found to be 98.96 ± 1.37.

Conclusion:

The proposed HPLC method may be used efficiently for routine and quality control analysis of rizatriptan benzoate in pharmaceutical formulations.

Physicochemical interaction of rifampicin and ritonavir-lopinavir solid dispersion: an in-vitro and ex-vivo investigation

OBJECTIVE

To investigate the in-situ physicochemical interaction of Rifampicin and Ritonavir - Lopinavir Solid dispersion administered for the treatment of comorbid conditions i.e. Tuberculosis and HIV/AIDS.

METHODS

pH-shift dissolution of Rifampicin (RIF) in presence of Ritonavir-Lopinavir solid dispersion (RL-SD) was carried out in USP phosphate buffer 6.8 and FaSSIF. Equilibrium and amorphous solubility were determined for the drugs. Pure drugs, their physical mixtures, and pH-shifted co-precipitated samples were characterized using DSC, PXRD, and FTIR. Fluorescence spectroscopy was used to investigate drug-rich and drug-lean phases. In-vitro and ex-vivo flux studies were also carried out.

RESULTS

The results showed significant differences in the solubility and dissolution profiles of RTV and LOP in the presence of RIF, while RIF profile remained unchanged. Amorphicity, intermolecular interaction and aggregate formation in pH-shifted samples were revealed in DSC, XRD and FTIR analysis. Fluorescence spectroscopy confirmed the formation of drug-rich phase upon pH-shift. In-vitro and ex-vivo flux studies revealed significant reduction in the flux of all the drugs when studied in presence of second drug.

CONCLUSION

RIF, RTV and LOP in presence of each other on pH-shift, results in co-precipitation in the amorphous form (miscible) which leads to reduction in the highest attainable degree of supersaturation. This reduction corresponds to the mole fraction of the RIF, RTV and LOP within the studied system. These findings suggest that the concomitant administration of these drugs may lead to physicochemical interactions and possible ineffective therapy.

Computational-Based Polyphenol Therapy for Nonsmall Cell Lung Cancer: Naringin Coamorphous Systems for Solubility and Bioavailability Enhancement

In this research, we utilized molecular simulations to create co-amorphous materials (CAMs) of ceritinib (CRT) with the objective of improving its solubility and bioavailability. We identified naringin (NRG) as a suitable co-former for CRT CAMs based on binding energy and intermolecular interactions through computational modeling. We used the solvent evaporation method to produce CAMs of CRT and NRG, expecting to enhance both solubility and bioavailability simultaneously. The solid-state characterization using techniques like differential scanning calorimeter, X-ray powder diffraction, and Fourier-transform infrared spectroscopy affirmed the formation of a single amorphous phase and the presence of intermolecular interactions between CRT and NRG in the CAMs. These materials remained physically stable for up to six months under dry conditions at 40 °C. Moreover, the CAMs demonstrated significant improvements in the solubility and dissolution of CRT (specifically in the ratio CRT:NRG 1:2). This, in turn, led to an increase in cytotoxicity, apoptotic cells, and G0/G1 phase inhibition in A549 cells compared to CRT alone. Furthermore, CRT permeability is also improved twofold, as estimated by the everted gut sac method. The enhanced solubility of CAMs also positively affected the pharmacokinetic parameters. When compared to the physical mixture, the CAMs of CRT:NRG 2:1 exhibited a 2.1-fold increase in CRT exposure (AUC0-t) and a 2.4-fold increase in plasma concentration (Cmax).

Development and validation of LC-MS/MS method for estimating the pharmacokinetics, protein binding, and metabolic stability of soluble epoxide hydrolase inhibitor EC5026

EC5026 is a soluble epoxide hydrolase (SEH) inhibitor which is being developed clinically (Phase-1) as a first-in-class analgesic for the treatment of pain. In the present study, we report the development and validation of the LC-MS/MS method for the estimation of EC5026 from rat plasma. The developed method is simple, specific, and sensitive for the quantification of EC5026 from rat plasma. The method was applied to investigate in-vivo pharmacokinetics after single oral administration (P.O.) of EC5026 (5.0 mg/kg) in Wistar rats. Further, the in-vitro metabolic stability and rat plasma protein binding of EC5026 were evaluated using the developed method. The in-vitro results demonstrated a moderate clearance with a value of 10.8 mL/min/kg and half-life (t1/2) of 57.75 min. The results show moderate clearance by the liver manifesting in satisfactory oral bioavailability. The rat plasma protein binding was estimated to be 96.24% ± 0.97% and 96.38% ± 0.56% at 1 µM and 10 µM concentrations, respectively. The developed analytical method is expected to facilitate future pre-clinical, clinical investigations of EC5026.