Development and optimization of micro/nanoporous osmotic pump tablets

Development of Sinomenine Hydrochloride Sustained-release Pellet With Multiple Release Characteristics

Due to the gastrointestinal side effects, the clinical application of sinomenine hydrochloride (SH) in rheumatoid arthritis is limited. The elderly population constitutes the primary group affected by this disease, and within this demographic, there are significant variations in gastric emptying time. To reduce the influence of individual differences on drug efficacy and concurrently alleviate gastrointestinal side effects, the SH sustained-release pellets with multiple release characteristics were developed, which comprised both regular sustained-release pellets and enteric-coated sustained-release pellets. The drug-loaded layer formulation was optimized by full factorial design. With the optimal formulation, the drug-loaded pellets achieved a yield of 96.05%, an encapsulation efficiency of 83.36% for SH, a relative standard deviation of 3.26% in SH content distribution, an average roundness of 0.971 for the pellets, and the particle size span of 0.808. The pellets with a 4 h SH release profile in an acidic environment and pellets displaying 4 h acid resistance followed by an 8 h SH release behavior in the intestinal environment were individually prepared through in vitro dissolution tests. The results demonstrated stable and compliant dissolution behavior of the formulation, along with excellent stability and physical appearance. This research offers novel insights and references for the innovative formulation of SH.

Development and pharmacokinetic evaluation of osmotically controlled drug delivery system of Valganciclovir HCl for potential application in the treatment of CMV retinitis

Valganciclovir HCl (VGH) is the widely used drug for the treatment of cytomegalovirus (CMV) retinitis infection with an induction dose of 900 mg per oral (p.o.) twice a day and a maintenance dose of 900 mg (p.o.). This required dose of the drug also leads to multiple side effects due to repeated administration. The research was highlighted to develop, formulate, optimize, and evaluate single-core osmotic pump (SCOP) tablet of VGH with the dose of 450 mg to reduce dosing frequency and associated side effects. The decrease in dose also minimizes the hepatic and nephrotic load. The optimized batch of the formulation was subjected to comparative in vitro and in vivo evaluation. The tablet core composition is the primary influencer of the drug delivery fraction in a zero order, whereas the membrane characteristics control the drug release rate. In vivo pharmacokinetic studies revealed that the newly developed osmotic formulation has controlled zero-order release for 24 h with a single dose of 450 mg while the marketed formulation requires twice administration within 24 h to maintain the plasma concentration in the therapeutic window. The pharmacokinetic study demonstrated that the developed formulation has the area under curve (AUC) of 58.415 µg h/ml with single dose while the marketed formulation shows the AUC of about 37.903 µg h/ml and 31.983 µg h/ml for first and second dose, respectively. The large AUC demonstrates the extended release of drug with a single dose and effective plasma concentration. Hence, the developed formulation can be a promising option for the treatment of CMV retinitis with the minimum dose and dosing frequency.

Measuring Open Porosity of Porous Materials Using THz-TDS and an Index-Matching Medium

The porosity of porous materials is a critical quality attribute of many products ranging from catalysis and separation technologies to porous paper and pharmaceutical tablets. The open porosity in particular, which reflects the pore space accessible from the surface, is crucial for applications where a fluid needs to access the pores in order to fulfil the functionality of the product. This study presents a methodology that uses terahertz time-domain spectroscopy (THz-TDS) coupled with an index-matching medium to measure the open porosity and analyze scattering losses of powder compacts. The open porosity can be evaluated without the knowledge of the refractive index of the fully dense material. This method is demonstrated for pellets compressed of pharmaceutical-grade lactose powder. Powder was compressed at four different pressures and measured by THz-TDS before and after they were soaked in an index-matching medium, i.e., paraffin. Determining the change in refractive index of the dry and soaked samples enabled the calculation of the open porosity. The results reveal that the open porosity is consistently lower than the total porosity and it decreases with increasing compression pressure. The scattering losses reduce significantly for the soaked samples and the scattering centers (particle and/or pore sizes) are of the order of or somewhat smaller than the terahertz wavelength. This new method facilitates the development of a better understanding of the links between material properties (particles size), pellet properties (open porosity) and performance-related properties, e.g., disintegration and dissolution performance of pharmaceutical tablets.

Characterisation of pore structures of pharmaceutical tablets: A review

Traditionally, the development of a new solid dosage form is formulation-driven and less focus is put on the design of a specific microstructure for the drug delivery system. However, the compaction process particularly impacts the microstructure, or more precisely, the pore architecture in a pharmaceutical tablet. Besides the formulation, the pore structure is a major contributor to the overall performance of oral solid dosage forms as it directly affects the liquid uptake rate, which is the very first step of the dissolution process. In future, additive manufacturing is a potential game changer to design the inner structures and realise a tailor-made pore structure. In pharmaceutical development the pore structure is most commonly only described by the total porosity of the tablet matrix. Yet it is of great importance to consider other parameters to fully resolve the interplay between microstructure and dosage form performance. Specifically, tortuosity, connectivity, as well as pore shape, size and orientation all impact the flow paths and play an important role in describing the fluid flow in a pharmaceutical tablet. This review presents the key properties of the pore structures in solid dosage forms and it discusses how to measure these properties. In particular, the principles, advantages and limitations of helium pycnometry, mercury porosimetry, terahertz time-domain spectroscopy, nuclear magnetic resonance and X-ray computed microtomography are discussed.

Aqueous Polymer Dispersion Coating Used for Osmotic Pump Tablets: Membrane Property Investigation and IVIVC Evaluation

The objective of this study was to investigate the fundamental properties of propranolol hydrochloride osmotic pump tablets coated by aqueous polymer dispersion, simultaneously exploring the in vitro and in vivo correlation of the tablet. The physicochemical properties and parameters of aqueous polymer dispersion membranes (SEM, water uptake, and water vapor transmission coefficient) were investigated. In addition, the release behavior and the in vitro release and in vivo absorption profiles of the tablets coated by aqueous polymer dispersion were investigated by comparing with propranolol hydrochloride osmotic pump tablets coated by an organic solvent. Results showed that the similarity factor (f ₂) between cellulose acetate-coated tablet and Eudragit-coated tablet was 78.1, and f ₂ between cellulose acetate-coated tablet and Kollicoat-coated tablet was 77.6. The linear IVIVC of Eudragit-coated and Kollicoat-coated osmotic pump tablets was determined, which confirmed excellent correlation between the absorption in vivo and the drug release in vitro. Consequently, the membrane coated by aqueous polymer dispersion or organic solvent has similar in vitro release rates of controlled release. Also, compared with organic solvent coating, aqueous polymer dispersion has numerous advantages, such as reduced toxicity and no environmental damage. Therefore, the aqueous polymer dispersion technology has enormous potential as a replacement of organic solvent coating.

A novel asymmetric membrane osmotic pump capsule with in situ formed delivery orifices for controlled release of gliclazide solid dispersion system

In this study, a novel asymmetric membrane osmotic pump capsule of gliclazide (GLC) solid dispersion was developed to achieve a controlled drug release. The capsule shells were obtained by wet phase inversion process using cellulose acetate as semi-permeable membrane, glycerol and kolliphor P188 as pore formers, then filled with the mixture of GLC solid dispersion and pH modifiers. Differentiate from the conventional formulations, sodium carbonate was chosen as the osmotic agent and effervescent agent simultaneously to control the drug release, instead of the polymer materials. The ternary solid dispersion of GLC, with polyethylene glycol 6000 and kolliphor P188 as carriers, was prepared by solvent-evaporation method, realizing a 2.09-fold increment in solubility and dissolution rate in comparison with unprocessed GLC. Influence of the composition of the coating solution and pH modifiers on the drug release from the asymmetric membrane capsule (AMC) was investigated. The ultimate cumulative release of the optimal formulation reached 91.32% in an approximately zero-order manner. The osmotic pressure test and dye test were conducted to validate the drug release mechanism from the AMC. The in vivo pharmacokinetic study of the AMC indicated a 102.66±10.95% relative bioavailability compared with the commercial tablet, suggesting the bioequivalence between the two formulations. Consequently, the novel controlled delivery system with combination of solid dispersion and AMC system is capable of providing a satisfactory alternative to release the water-insoluble drugs in a controlled manner.

Model drug as pore former for controlled release of water-soluble metoprolol succinate from ethylcellulose-coated pellets without lag phase: opportunities and challenges

The objective of the present study was to evaluate the feasibility of using model drug metoprolol succinate (MS) as a pore former to modify the initial lag phase (i.e., a slow or non-release phase in the first 1-2 h) associated with the drug release from coated pellets. MS-layered cores with high drug-layering efficiency (97% w/w) were first prepared by spraying a highly concentrated drug aqueous solution (60% w/w, 70°C) on non-pareils without using other binders. The presence of MS in ethylcellulose (EC) coating solution significantly improved the coating process by reducing pellets sticking, which often occurs during organic coating. There may be a maximum physical compatibility of MS with EC, and the physical state of the drug in the functional coating layer of EC/MS (80:20) was simultaneously crystalline and non-crystalline (amorphous or solid molecule solution). The lag phase associated with hydroxypropylcellulose (HPC) as a pore former was not observed when MS was used as a pore former. The drug release from EC/MS-coated pellets was pH independent, inversely proportional to the coating levels, and directly related to the pore former levels. The functional coating layer with MS as a pore former was not completely stabilized without curing. Curing at 60°C for 1 day could substantially improve the stability of EC/MS-coated pellets. The physical state of the drug in the free film of EC/MS (85:15) changed partially from amorphous to crystal when cured at 60°C for 1 day, which should be attributed to the incompatibility of the drug with EC.

Development and physicochemical characterization of saquinavir mesylate solid dispersions using Gelucire 44/14 or PEG 4000 as carrier

Solid dispersions of saquinavir mesylate containing either Gelucire® 44/14 or poly(ethylene glycol) (PEG) 4000, or mixtures of each carrier with Tween 80 or polyvinyl pyrrolidone (PVP) K30 were prepared in order to enhance the drug dissolution rate. These systems were prepared by the melting method and characterized by X-ray powder diffraction, microscopical techniques, and Raman spectroscopy aiming to establish a relationship between physicochemical and dissolution properties under different cooling conditions. Modifications in degree of crystalline order/disorder over time were observed in preparations with both carriers. Overall, formulations cooled and stored at -20 °C showed less variation in dissolution rates than those at 25 °C. Although Tween 80 has enhanced the known self-emulsifying properties of Gelucire® 44/14, its combination with PEG 4000 displayed miscibility problems. The addition of PVP K30 was not the most effective approach in enhancing the dissolution in early steps; however, the drug dissolution was stable after 7 days of storage at 25 °C. The combination of PEG 4000 and PVP K30 maintained the dissolution properties for 60 and 90 days at 25 °C/95% relative humidity and 40 °C/75% (f₂ values >50), respectively.

Fabrication of chitosan--polyacrylic acid complexes as polymeric osmogents for swellable micro/nanoporous osmotic pumps

AIM

The aims of this study were to prepare and evaluate chitosan-polyacrylic acid complex (CS-PAA) as polymeric osmogents for swellable micro/nanoporous osmotic pump propranolol tablets.

METHODS

The complexes were characterized and evaluated for their swelling characteristics. The selected complexes were incorporated into the core propranolol tablets as polymeric osmogents. The core tablets were formulated, compressed as monolithic and two-layered tablets, and finally coated with cellulose acetate containing PEG 400 and PVP K30 as plasticizers and pore formers, respectively. As a final point, the drug release was determined.

RESULTS

A direct correlation was found between the CS content in the complex and the maximum swelling force and swelling ratio of the complex mixture. In vitro drug release revealed that the percent drug release increased with the amount of osmogent in the two-layered tablets. Drug release could be prolonged up to 12h and conformed to the USP 31 criteria. In contrast, percent release decreased with the increasing amount of complexes in monolithic tablets. It was postulated that two opposing mechanisms were involved. Following water uptake, the complexes of polymers swelled and pushed the drug out of the tablets, and the drug bound to the polymer network and remained in the tablets.

CONCLUSIONS

The results indicated that the complex of CS-PAA at optimal proportion and amount was a promising polymeric osmogent for a zero-order controlled release from two-layered swellable micro/nanoporous osmotic pump tablets.