Navnit Shah

Self-emulsifying drug delivery systems (SEDDS) with polyglycolyzed glycerides for improving in vitro dissolution and oral absorption of lipophilic drugs

Abstract The ability of polyglycolyzed glycerides (PGG) with varying fatty acid and polyethylene glycol (PEG) chain lengths to produce the self-emulsification of oil in water has been investigated. The quality of the resulting emulsions depends on the oil and emulsifier pair selected. These self-emulsifying drug delivery systems (SEDDS) were prepared using various concentrations of PGG as emulsifiers. Two oils, a medium-chain triglyceride (Neobee M5) and Peanut Oil, were chosen as the vehicle for the drug. A lipophilic drug with excellent oil solubility was selected for this study. The droplet size distribution, the release rate of the drug and the oil/water partition coefficient (PC o/w ) of the drug in these systems were evaluated for the SEDDS obtained. The results indicate that PGG are effective emulsifiers for SEDDS. Droplet particle size in combination with droplet polarity in the emulsion are prerequisites for efficient SEDDS. The PC o/w of the drug from these SEDDS is helpful in evaluating these properties. A phase diagram was used to obtain the optimum concentrations of drug, oil and emulsifying agent. The results obtained with PGG were compared with previously reported SEDDS for the efficiency of drug release (Bachynsky et al., (1989) AAPS Annual Meeting). In vitro dissolution and in vivo absorption of a lipophilic drug from SEDDS are compared with those properties of other dosage forms.

Development of a Novel Controlled-Release System for Gastric Retention

AbstractPurpose. We report on the development of a novel controlled-release gastric retention system, which consists of a matrix tablet, coated with a permeable membrane. When immersed in simulated gastric fluid, the tablet expands. The tablet remains expanded for eighteen to twenty hours, during which time the drug is released. The tablet then either disintegrates into fragments or loses its integrity. Methods. Tablets containing a soluble drug (chlorpheniramine maleate, i.e., CPM) and a poorly soluble drug (riboflavin 5′ phosphate, i.e., R5′P) were compressed. They were coated with a permeable and elastic polymer (Eudragit®). Dissolution profiles of these tablets were studied. The changes in the pH, viscosity, and deformation characteristics as a function of time were measured. Results. Carbopol® provided a firm structure to the swollen tablet. Polyvinyl pyrrolidone XL (PVP XL) contributed to the swelling of the tablet. Carbonates provided the initial alkaline micro-environment for Carbopol® to gel and conferred buoyancy to the tablet. Coating provided the support needed for the core to remain intact during drug release and, at the same time, it allowed drug release due to its permeable nature. During release, the gelling properties of Carbopol® lessened, resulting in a decrease in the firmness of the core. This was evident from the decrease in the viscosity of the core. The energy required at 50% strain also decreased as the drug release progressed. Conclusions. When this tablet is ingested, the chances of its elimination through the pylorus should be greatly reduced due to tablets expansion, and due to its disintegration or loss in integrity it should then be expelled out of the stomach at the end of the drug release.

Controlled-Release Drug Delivery Systems for Prolonged Gastric Residence: An Overview

(1996). Controlled-Release Drug Delivery Systems for Prolonged Gastric Residence: An Overview. Drug Development and Industrial Pharmacy: Vol. 22, No. 6, pp. 531-539.

Controlled Drug Delivery by Biodegradable Poly(Ester) Devices: Different Preparative Approaches

There has been extensive research on drug delivery by biodegradable polymeric devices since bioresorbable surgical sutures entered the market two decades ago. Among the different classes of biodegradable polymers, the thermoplastic aliphatic poly(esters) such as poly(lactide) (PLA), poly(glycolide) (PGA), and especially the copolymer of lactide and glycolide referred to as poly(lactide-co-glycolide) (PLGA) have generated tremendous interest because of their excellent biocompatibility, biodegradability, and mechanical strength. They are easy to formulate into various devices for carrying a variety of drug classes such as vaccines, peptides, proteins, and micromolecules. Most importantly, they have been approved by the United States Food and Drug Administration (FDA) for drug delivery. This review presents different preparation techniques of various drug-loaded PLGA devices, with special emphasis on preparing microparticles. Certain issues about other related biodegradable polyesters are discussed.

Hot melt extrusion (HME) for amorphous solid dispersions: Predictive tools for processing and impact of drug–polymer interactions on supersaturation

The processing parameters for HME have been evaluated and the impact of solid state intermolecular drug-polymer interactions on supersaturation has been investigated. Poorly water soluble drugs Indomethacin (IND), Itraconazole (ITZ), and Griseofulvin (GSF) and hydrophilic polymers - Eudragit EPO, Eudragit L-100-55, Eudragit L-100, HPMCAS-LF, HPMCAS-MF, Pharmacoat 603, and Kollidon VA-64 were selected for this study. Solubility parameters calculations (SPCs), differential scanning calorimetry (DSC), and rheological analysis of drug-polymer physical mixtures (PMs) was performed. The solid dispersions were manufactured using HME and characterized by powder X-ray diffraction (PXRD), polarized light microscopy (PLM), Fourier transform infra-red (FTIR) Spectroscopy, and dissolution study. Results obtained by DSC correlated well with SPC, showing single glass transition temperatures for all the PMs except ITZ in Eudragit EPO that depicted the highest difference in solubility parameters. The zero rate viscosity (η₀) was dependent on the melting point and consequently the state of the drug in the polymer at the softening temperature. The η₀ of PMs was useful to estimate the processing conditions for HME and to produce transparent glassy HMEs from most of the PMs. The amorphous conversion due to HME was confirmed by PXRD and PLM. The solid state drug-polymer interactions occurred during HME could be confirmed by FTIR analysis. Highest supersaturation could be achieved for IND, ITZ, and GSF using Eudragit EPO, HPMCAS-LF, and Eudragit L-100-55, respectively where relatively higher stretching of the carbonyl peaks was observed by FTIR. Thus, the highest dissolution rate and supersaturation of poorly water soluble drugs could be attributed to drug-polymer interactions occurred during HME.

A biodegradable injectable implant for delivering micro and macromolecules using poly (lactic-co-glycolic) acid (PLGA) copolymers

Abstract Biodegradable polymers are used in diffusion controlled, swelling controlled and chemically controlled delivery systems. In this study, PLGA copolymers were used in a formulation which forms a gel matrix immediately on contact with aqueous fluids. This property of the formulation can circumvent the need for making a surgical incision to implant the matrix. The gel matrix thus formed will release the drug slowly (over a period of weeks to months) and ultimately biodegrade depending on the composition of the polymer used. In vitro release studies using small molecules and macromolecules, such as proteins, indicate that the drug release is influenced by the concentration of the polymer, physico-chemical properties of the drug, method of incorporation of the drug in the formulation and the presence of other excipients. The drug release can therefore be modified to suit the desired release characteristics. This novel formulation design for a biodegradable injectable implant can provide prolonged release while avoiding the necessity for surgical procedures.

Improved Human Bioavailability of Vemurafenib, a Practically Insoluble Drug, Using an Amorphous Polymer-Stabilized Solid Dispersion Prepared by a Solvent-Controlled Coprecipitation Process

The present work deals with improving the solubility of vemurafenib, a practically insoluble drug, by converting it into an amorphous-solid dispersion using a solvent-controlled precipitation process. The dispersion containing vemurafenib and hypromellose acetate succinate (HPMCAS), an enteric polymer, is termed microprecipitated bulk powder (MBP), in which the drug is uniformly dispersed within the polymeric substrate. HPMCAS was found to be the most suitable polymer for vemurafenib MBP, among a series of enteric polymers based on superior physical stability and drug-release characteristics of the MBP. The MBP provided a greater rate and extent of dissolution than crystalline drug, reaching an apparent drug concentration of 28-35 µg/mL, almost 30-fold higher than solubility of crystalline drug at 1 µg/mL. The supersaturation was also maintained for more than 4 h. Upon exposure to high temperature and humidity, the MBP was destabilized, resulting in crystallization and lower dissolution rate. The control of moisture and temperature is essential to maintain the stability of the MBP. In a relative human bioavailability study, vemurafenib MBP provided a four- to fivefold increase in exposure compared with crystalline drug. Improving solubility with an amorphous-solid dispersion is a viable strategy for the development of practically insoluble compounds.

Evaluation of solid state properties of solid dispersions prepared by hot-melt extrusion and solvent co-precipitation

The solid state properties of solid dispersions of Compound A in hypromellose acetate succinate (HPMC-AS) prepared by hot-melt extrusion (HME) and solvent co-precipitation (CP) processes were evaluated using powder X-ray diffractometry (PXRD), thermal analysis, optical microscopy, scanning electron microscopy (SEM), FT-IR and Raman spectroscopy, water vapor sorption analyzer, and surface area by BET. PXRD indicated that both processes converted the crystalline drug into amorphous solid dispersions with a glass transition temperature around 104-107 degrees C and both products have similar spectroscopic and hygroscopic properties. The two products have similar true densities; however, the CP product is more porous and has a larger specific surface area than the HME product, as indicated by the BET results and SEM micrographs. Dissolution study using USP apparatus 2 showed that the CP product had a faster dissolution profile, but slower intrinsic dissolution rate than the HME product. The two products have acceptable physical stability after storage in 40 degrees C/75% RH chamber for 3 months. However, the HME product is more stable than the CP product in aqueous suspension formulation.

Improving the Dissolution Rate of Poorly Water Soluble Drug by Solid Dispersion and Solid Solution—Pros and Cons

The solid dispersions with poloxamer 188 (P188) and solid solutions with polyvinylpyrrolidone K30 (PVPK30) were evaluated and compared in an effort to improve aqueous solubility and bioavailability of a model hydrophobic drug. All preparations were characterized by differential scanning calorimetry, powder X-ray diffraction, intrinsic dissolution rates, and contact angle measurements. Accelerated stability studies also were conducted to determine the effects of aging on the stability of various formulations. The selected solid dispersion and solid solution formulations were further evaluated in beagle dogs for in vivo testing. Solid dispersions were characterized to show that the drug retains its crystallinity and forms a two-phase system. Solid solutions were characterized to be an amorphous monophasic system with transition of crystalline drug to amorphous state. The evaluation of the intrinsic dissolution rates of various preparations indicated that the solid solutions have higher initial dissolution rates compared with solid dispersions. However, after storage at accelerated conditions, the dissolution rates of solid solutions were lower due to partial reversion to crystalline form. The drug in solid dispersion showed better bioavailability in comparison to solid solution. Therefore, considering physical stability and in vivo study results, the solid dispersion was the most suitable choice to improve dissolution rates and hence the bioavailability of the poorly water soluble drug.

Solid-state plasticization of an acrylic polymer with chlorpheniramine maleate and triethyl citrate.

The influence of in situ plasticization of chlorpheniramine maleate (CPM) on Eudragit RS PO from hot-melt extruded matrix tablets, and from compressed granules prepared by thermal processing was investigated. CPM was studied as both a model drug substance and as a solid-state plasticizer for the acrylic polymer. Triethyl citrate (TEC) was incorporated into the polymer blend as a liquid plasticizer for the polymer. The influence of TEC and CPM concentration on the dissolution properties of CPM tablets was investigated. The glass transition temperature (T(g)) of the samples was determined by modulated differential scanning calorimetry (MDSC). The morphologies of the granules formed by hot-melt extrusion and hot-melt granulation processes were investigated by scanning electron microscopy. The addition of 12% TEC to the polymer reduced the T(g) by 32.5 degrees C, while the reduction in the T(g) for the same level of CPM was 16.4 degrees C. The effect of TEC levels on drug release was dependent on the tablet preparation method. At high TEC levels, the release rate of CPM decreased in tablets prepared by direct compression and tablets made from compressed granules that had been prepared by high shear hot-melt granulation. However, the CPM release rate increased from hot-melt extruded tablets with increasing blends of plasticizer in the extruded tablets. An increase in the CPM content in the tablets resulted in an increase in the drug release rate. During high shear hot-melt granulation, the model drug adhered to the polymer to form a porous discontinuous structure. Following hot-melt extrusion, the drug was distributed at a molecular level in the continuous polymeric structure. The influence of both CPM and TEC levels on the drug release rate from these polymeric drug delivery systems was shown to be a function of whether the granules or tablets were formed by either hot-melt granulation or hot-melt extrusion, as well as the plasticization effects of both TEC and CPM on the acrylic polymer.