Development and evaluation of osmotically controlled oral drug delivery system of glipizide

Modelling the controlled drug release of push-pull osmotic pump tablets using DEM

The push-pull osmotic pump tablet is a promising drug delivery approach, offering advantages over traditional dosage forms in achieving consistent and predictable drug release rates. In the current study, the drug release process of push-pull osmotic pump tablets is modelled for the first time using the discrete element method (DEM) incorporated with a microscopic diffusion-induced swelling model. The effects of dosage and formulation design, such as delivery orifice size, drug-to-polymer ratio, tablet surface curvature, friction between particles and cohesion of polymer particles, on the drug release performance are systematically analysed. Numerical results reveal that an enlarged delivery orifice significantly increases both the total drug release and the drug release rate. Moreover, the larger the swellable particle component in the tablet, the higher the drug release rate. Furthermore, the tablet surface curvature is found to affect the drug release profile, i.e. the final drug release percentage increases with the increasing tablet surface curvature. It is also found that the drug release rate could be controlled by adjusting the inter-particle friction and the cohesion of polymer particles in the formulation. This DEM study offers valuable insights into the mechanisms governing drug release in push-pull osmotic pump tablets.

Osmotic Pump Drug Delivery Systems-A Comprehensive Review

In the last couple of years, novel drug delivery systems (NDDS) have attracted much attention in the food and pharmaceutical industries. NDDS is a broad term that encompasses many dosage forms, one of which is osmotic pumps. Osmotic pumps are considered to be the most reliable source of controlled drug delivery, both in humans and in animals. These pumps are osmotically controlled and release active agents through osmotic pressure. To a large extent, drug release from such a system is independent of gastric fluids. Based on such unique properties and advantages, osmotic pumps have made their mark on the pharmaceutical industry. This review summarizes the available osmotic devices for implantation and osmotic tablets for oral administration.

Design, development and characterization of interpenetrating polymer network hydrogel bead for controlled release of glipizide drug

In the current study, a novel interpenetrating polymer network (IPN) hydrogel bead was developed by encapsulation of antidiabetic drug glipizide using sodium alginate (SAL) and xanthan gum (XAG) biopolymers by ionotropic gelation technique with calcium chloride as cross-linking agent. In light of the fact that IPN hydrogel beads posses greater benefits in controlling the release of such short acting drug, sodium alginate and xanthan gum IPN hydrogel beads were prepared at different mass ratios (SAL:XAG =10:0, 9:1, 8:2, 7:3, 6:4, 5:5). Similarly, drug-loaded IPN hydrogel beads were also developed. The prepared hydrogel beads were investigated using Fourier transform infrared spectroscopy, X-ray powder diffraction, and thermogravimetric studies to understand the type of interactions between the composite beads. Surface morphology changes were studied by scanning electron microscopy. The particle size, drug entrapment efficiency, and swelling behavior of prepared hydrogel beads were also studied. Based on In-vitro drug dissolution studies, it was observed that SXF4 preparation containing SAL and XAG polymers at 7:3 ratio showed extended drug release of 97.53% at 9 h. This study demonstrated that inclusion of XAG has extended the drug release and able to achieve zero-order drug release profile.

Repairing the heart: State-of the art delivery strategies for biological therapeutics

Myocardial infarction (MI) is one of the leading causes of mortality worldwide. It is caused by an acute imbalance between oxygen supply and demand in the myocardium, usually caused by an obstruction in the coronary arteries. The conventional therapy is based on the application of (a combination of) anti-thrombotics, reperfusion strategies to open the occluded artery, stents and bypass surgery. However, numerous patients cannot fully recover after these interventions. In this context, new therapeutic methods are explored. Three decades ago, the first biologicals were tested to improve cardiac regeneration. Angiogenic proteins gained popularity as potential therapeutics. This is not straightforward as proteins are delicate molecules that in order to have a reasonably long time of activity need to be stabilized and released in a controlled fashion requiring advanced delivery systems. To ensure long-term expression, DNA vectors-encoding for therapeutic proteins have been developed. Here, the nuclear membrane proved to be a formidable barrier for efficient expression. Moreover, the development of delivery systems that can ensure entry in the target cell, and also correct intracellular trafficking towards the nucleus are essential. The recent introduction of mRNA as a therapeutic entity has provided an attractive intermediate: prolonged but transient expression from a cytoplasmic site of action. However, protection of the sensitive mRNA and correct delivery within the cell remains a challenge. This review focuses on the application of synthetic delivery systems that target the myocardium to stimulate cardiac repair using proteins, DNA or RNA.

Zero-order drug delivery: State of the art and future prospects

Pharmaceutical drugs are an important part of the global healthcare system, with some estimates suggesting over 50% of the world's population takes at least one medication per day. Most drugs are delivered as immediate-release formulations that lead to a rapid increase in systemic drug concentration. Although these formulations have historically played an important role, they can be limited by poor patient compliance, adverse side effects, low bioavailability, or undesirable pharmacokinetics. Drug delivery systems featuring first-order release kinetics have been able to improve pharmacokinetics but are not ideal for drugs with short biological half-lives or small therapeutic windows. Zero-order drug delivery systems have the potential to overcome the issues facing immediate-release and first-order systems by releasing drug at a constant rate, thereby maintaining drug concentrations within the therapeutic window for an extended period of time. This release profile can be used to limit adverse side effects, reduce dosing frequency, and potentially improve patient compliance. This review covers strategies being employed to attain zero-order release or alter traditionally first-order release kinetics to achieve more consistent release before discussing opportunities for improving device performance based on emerging materials and fabrication methods.

Bioretrosynthesis of Functionalized N-Heterocycles from Glucose via One-Pot Tandem Collaborations of Designed Microbes

The design of multistrain systems has markedly expanded the prospects of using long biosynthetic pathways to produce natural compounds. However, the cooperative use of artificially engineered microbes to synthesize xenobiotic chemicals from renewable carbohydrates is still in its infancy. Here, a microbial system is developed for the production of high-added-value N-heterocycles directly from glucose. Based on a retrosynthetic analysis, eleven genes are selected, systematically modulated, and overexpressed in three Escherichia coli strains to construct an artificial pathway to produce 5-methyl-2-pyrazinecarboxylic acid, a key intermediate in the production of the important pharmaceuticals Glipizide and Acipimox. Via one-pot tandem collaborations, the designed microbes remarkably realize high-level production of 5-methyl-2-pyrazinecarboxylic acid (6.2 ± 0.1 g L-1) and its precursor 2,5-dimethylpyrazine (7.9 ± 0.7 g L-1). This study is the first application of cooperative microbes for the total biosynthesis of functionalized N-heterocycles and provides new insight into integrating bioretrosynthetic principles with synthetic biology to perform complex syntheses.

Preparation, Optimization and In vitro Evaluation of Glipizide Nanoparticles Integrated with Eudragit RS-100

BACKGROUND

Solubility is an important criterion for drug efficacy, independent of the route of administration. It also poses a major challenge for pharmaceutical industries, which are developing new pharmaceutical products, since 40% of the active substances being identified are either insoluble or poorly soluble in aqueous media.

OBJECTIVE

The objective of this study was to develop nanoformulation of glipizide drugloaded nanoparticles providing controlled release formulation.

METHOD

Nanoparticles were prepared by the solvent evaporation method. Eudragit RS100, a nonbiodegradable polymer with varying ratios was used for making the formulation. The effect of key formulation variables on the particle size and entrapment efficiency and drug loading of nanoparticles were studied by using factorial design.

RESULTS

DSC thermograms indicate that glipizide was dispersed in an amorphous state in the polymer. TEM study indicates that the nanoparticles were in spherical shape. The mean diameter was dependent on the presence of the amount of Eudragit RS100 and viscosity of the organic phase. The in vitro study showed that the cumulative drug release was from 69.52-81.44 % in 10 hrs at pH 6.8 in phosphate buffer respectively.

CONCLUSION

The developed NPs could reduce dose frequency, decrease side effects, and improve patient compliance. Using factorial design, maximum entrapment efficiency with minimum particle size could be achieved with a few experiments.

Design and Evaluation of Hydrophilic Matrix System for pH-Independent Sustained Release of Weakly Acidic Poorly Soluble Drug

The aim of this research was to design and evaluate a hydrophilic matrix system for sustained release of glipizide, a weakly acidic poor soluble drug. A combination of inclusion complexation and microenvironmental pH modification techniques was utilized to improve the dissolution and pH-independent release of glipizide. Hydroxypropyl-β-cyclodextrin (HP-β-CD) was used as the complexation agent while sodium citrate and magnesium oxide (MgO) were used as model pH modifiers. The hydrophilic matrix tablets were prepared by powder direct compression and evaluated by in vitro dissolution study respectively in pH 6.8 and pH 1.2 dissolution media. The formulations containing MgO exhibited increased cumulative drug release from less than 40% in the reference formulation to 90% within 24 h in acidic media (pH 1.2). The release profile in acidic media was similar to the alkaline media (pH 6.8) with a similarity factor (f₂) of 55.0, suggesting the weakening of the effect of pH on the dissolution efficiency of glipizide. The release profile fitted well into the Higuchi model and the dominant mechanism of drug release was Fickian diffusion while case II transport/polymer relaxation occurred. In conclusion, combining inclusion complexation agents and pH modifiers had improved the dissolution of glipizide as well as achieved the pH-independent release profile.

Study of the Mucoadhesive Potential of Carbopol Polymer in the Preparation of Microbeads Containing the Antidiabetic Drug Glipizide

The present investigation was aimed at exploitation of the mucoadhesive potential of carbopol 934P polymer in developing microbeads of glipizide (GLP) for its effectivity in controlling blood sugar in diabetic patients. Various batches of GLP beads were prepared by an emulsion-solvent evaporation technique using the release-retarding polymer carbopol and subjected to a systematic evaluation such as physical characterization, ex vivo mucoadhesion, hydration and erosion test, and in vitro drug release; and instrumental and in vivo studies were performed with the best formulation. The highest yield and loading efficiency were observed as 94 and ∼90%, respectively. The mean particle size of the microbeads ranged from 832 to 742 μm. The oval shape of the microbeads with slight roughness was apparent in the SEM micrograph. The release period was extended till 18 h. In vitro release of the drug from the beads followed the diffusion and erosion mechanism. In the oral glucose tolerance test (OGTT), there is a significant (p < 0.01) reduction in fasting blood glucose levels in Wistar rat and guinea pig in comparison with that using the marketed product. Results indicated that process parameters-drug-polymer ratio, concentration of the surfactant, and stirring speed-controlled the various characteristics of the microparticles. The mucoadhesivity test ensured strong adherence of the beads to the mucosal membrane in pH 1.2 for a prolonged period. Owing to the mucoadhesivity of carbopol 934P, prolonged release of GLP and reduction of fasting sugar in the animal model were observed to a satisfactory level, and thus, management of diabetes in a better manner is expected with this new formulation.

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.

Controlled porosity solubility modulated osmotic pump tablets of gliclazide

A system that can deliver drug at a controlled rate is very important for the treatment of various chronic diseases such as diabetes, asthma, and heart disease. Poorly water-soluble drug with pH-dependent solubility such as gliclazide (GLZ) offers challenges in the controlled-release formulation because of low dissolution rate and poor bioavailability. Solid dispersion (SD) of GLZ consisted of hydroxypropyl cellulose (HPC-SSL) as a polymeric solubilizer was manufactured by hot melt extrusion (HME) technology. Then, controlled porosity osmotic pump (CPOP) tablet of gliclazide was designed to deliver drug in a controlled manner up to 16 h. The developed formulation was optimized for type and level of pore former and coating weight gain. The optimized formulation was found to exhibit zero order kinetics independent of pH and agitation speed but depends on osmotic pressure of dissolution media indicated that mechanism of drug release was osmotic pressure. The in vivo performance prediction of developed formulation using convolution approach revealed that the developed formulation was superior to the existing marketed extended-release formulation in terms of attaining steady state plasma levels and indicated adequate exposure in translating hypoglycemic response. The prototype solubilization method combined with controlled porosity osmotic pump based technique could provide a unique way to increase dissolution rate and bioavailability of many poorly water-soluble, narrow therapeutic index drugs used in diabetes, cardiovascular diseases, etc.

Development of floating chitosan-xanthan beads for oral controlled release of glipizide

Introduction:

The aim of the present work was to develop controlled release, floating and mucoadhesive beads of glipizide by using the polyionic complexation technique. Plasma half-life of glipizide being 2–4 h was selected for development of controlled release dosage form.

Methods:

Formulation batches were designed by employing chitosan as cationic and xanthan gum as anionic polymers. In vitro drug release was evaluated for the period of 24 h in phosphate buffer pH 7.4.

Results:

Sustained release of drug was observed in all formulation batches with % drug release ranging from 87.50% to 100.67%, no significant effect on the drug release was observed after varying chitosan to xanthan gum ratio. Encapsulation efficiency was found to be in the range of 79.48 ± 1.10–94.48 ± 1.52. In vitro bioadhesion studies showed that beads had satisfactory bioadhesive strength ranging from 67.11% ± 1.73% to 93.12% ± 1.56%. Buoyancy studies revealed that beads possess comparable floating capacity in the gastric fluids. Swelling kinetics was carried in pH 1.2 and 7.4 buffers. Significant difference (P < 0.05) in swelling kinetics was observed. Drug to polymer interaction was analyzed by Fourier transform infrared spectroscopy and differential scanning calorimetry studies. Scanning electron microscopy studies revealed that formed beads were discrete with rough and wrinkled surfaces.

Conclusions:

In conclusion, beads were successfully formed by employing chitosan and xanthan gum and showed to possess sustained release effect. Beads also showed pH dependent swelling kinetics, this property can also be applied for the drugs which are susceptible to the acidic environment in the stomach, and comparable bioadhesive and floating properties were also observed.

Development of an oral push-pull osmotic pump of fenofibrate-loaded mesoporous silica nanoparticles

In this study, mesoporous silica nanoparticles (MSNs) were used to prepare an oral push–pull osmotic pump. Fenofibrate, the selected model drug, was firstly loaded into the MSNs, followed by a suspending agent consisting of a drug layer of push–pull osmotic pump. Fenofibrate-loaded MSNs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption/desorption analysis, differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD) analysis, and Fourier-transform infrared (FT-IR) spectroscopy. Polyethylene oxide of molecular weight (MW) 100,000 and polyethylene oxide of MW 6,000,000 were selected as the suspending agent and the expanding agent, respectively. Cellulose acetate was used as the semipermeable membrane, along with polyethylene glycol 6,000 to increase the flexibility and control the membrane permeability. The in vitro dissolution studies indicated that the osmotic pump tablet combined with MSNs was able to deliver fenofibrate in an approximately zero-order manner in 24 hours. A pharmacokinetic study showed that, although the maximum plasma concentration of the osmotic pump was lower than that of the reference formulation, the relative bioavailability was increased, indicating that the osmotic pump was more efficient than the reference tablets. Therefore, using MSNs as a carrier for poorly water-soluble drugs is an effective method for preparing osmotic pump tablets.

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.

Formulation and evaluation of controlled porosity osmotic pump for oral delivery of ketorolac

Background:

The osmotic drug delivery systems suitable for oral administration typically consist of a compressed tablet core that is coated with a semipermeable membrane that has an orifice drilled on it by means of a laser beam or mechanical drill. Ketorolac is a nonsteroidal agent with powerful analgesic. Oral bioavailability of ketorolac was reported to be 90% with very low hepatic first-pass elimination; the biological half-life of 4-6 hours requires frequent administration to maintain the therapeutic effect.

Aim:

The aim of the current study was to design a controlled porosity osmotic pump (CPOP)based drug delivery system for controlled release of an NSAID agent, ketorolac tromethamine, which is expected to improve patient compliance due to reduced frequency; it also eliminates the need for complicated and expensive laser drilling and maintain continuous therapeutic concentration.

Design:

The CPOP was designed containing pore-forming water-soluble additives in the coating membrane, which after coming in contact with water, dissolve, resulting in an in situ formation of a micro porous structure.

Materials and Methods:

The effect of different formulation variables, namely level of pore former (PVP), plasticizer (dibutyl phthalate) in the membrane, and membrane weight gain were studied.

Results and Conclusion:

Drug release was inversely proportional to the membrane weight but directly related to the initial concentration of pore former (PVP) in the membrane. Drug release was independent of pH and agitational intensity, but dependent on the osmotic pressure of the release media. Based on the in vitro dissolution profile, formulation F3C1 (containing 0.5 g PVP and 1 g dibutyl phthalate in coating membrane) exhibited Peppas kinetic with Fickian diffusion-controlled release mechanism with a drug release of 93.67% in 12 hours and hence it was selected as optimized formulation. SEM studies showed the formation of pores in the membrane. The formulations were stable after 3 months of accelerated stability studies. CPOP was designed for effective administration of drugs for prolonged period of time.

A two-step strategy to design high bioavailable controlled-release nimodipine tablets: the push-pull osmotic pump in combination with the micronization/solid dispersion techniques

In order to decrease the fluctuation of blood concentration and to increase the oral bioavailability of nimodipine (NMD), a two-step strategy including the push-pull osmotic pump (PPOP) method in combination with micronization and solid dispersion techniques, was used to prepare the controlled-release high-bioavailability solid dosages. The optimization of formulation and process was conducted by comparing effects of different solubilization methods on release behavior of NMD. The in vitro dissolution studies indicated that both the two strategies were able to deliver NMD in the predetermined zero-order manner from 2 to 12h, regardless of effects of release media and agitation rates. Although the Cmax values of two PPOP tablets were lower than that of the reference formulation, both the Tmax values were prolonged, demonstrating the prominent controlled release performance. In comparison with the commercial reference tables, the relative bioavailability of the two formulations was 67.0% and 121.1%, respectively, indicating the solid dispersion technique was more efficient than the micronization technique in terms of solubilization capability and absorption enhancement. In summary, the two-step strategy, combining the push-pull osmotic pump method with the solid dispersion technique, is a very effective method to prepare high bioavailable controlled-release formulations of the poorly soluble drugs, i.e. NMD, taking into account the therapeutical efficiency and safety.

Micro-porous surfaces in controlled drug delivery systems: design and evaluation of diltiazem hydrochloride controlled porosity osmotic pump using non-ionic surfactants as pore-former

The major problem associated with conventional drug delivery systems is unpredictable plasma concentrations. The aim of this study was to design a controlled porosity osmotic pump (CPOP) of diltiazem hydrochloride to deliver the drug in a controlled manner. CPOP tablets were prepared by incorporation of drug in the core and subsequent coating with cellulose acetate as semi-permeable membrane. Non-ionic surfactants were applied as pore-formers as well. The effect of pore-formers concentration on the in vitro release of diltiazem was also studied. The formulations were compared based on four comparative parameters, namely, total drug released after 24 h (D24 h), lag-time (tL), squared correlation coefficient of zero order equation (RSQzero) and mean percent deviation from zero order kinetic (MPDzero). Results of scanning electron microscopy studies exhibited formation of pores in the membrane from where the drug release occurred. It was revealed that drug release rate was directly proportional to the concentration of the pore-formers. The value of D24 h in the formulations containing Tween 80 (10%) and Brij 35 (5%) were found to be more than 94.9%, and drug release followed zero order kinetic (RSQzero > 0.99 and MPDzero < 8%) with acceptable tL (lower than 1 h).

Osmotic drug delivery system as a part of modified release dosage form

Conventional drug delivery systems are known to provide an immediate release of drug, in which one can not control the release of the drug and can not maintain effective concentration at the target site for longer time. Controlled drug delivery systems offer spatial control over the drug release. Osmotic pumps are most promising systems for controlled drug delivery. These systems are used for both oral administration and implantation. Osmotic pumps consist of an inner core containing drug and osmogens, coated with a semipermeable membrane. As the core absorbs water, it expands in volume, which pushes the drug solution out through the delivery ports. Osmotic pumps release drug at a rate that is independent of the pH and hydrodynamics of the dissolution medium. The historical development of osmotic systems includes development of the Rose-Nelson pump, the Higuchi-Leeper pumps, the Alzet and Osmet systems, the elementary osmotic pump, and the push-pull system. Recent advances include development of the controlled porosity osmotic pump, and systems based on asymmetric membranes. This paper highlights the principle of osmosis, materials used for fabrication of pumps, types of pumps, advantages, disadvantages, and marketed products of this system.

Osmotic pellet system comprising osmotic core and in-process amorphized drug in polymer-surfactant layer for controlled delivery of poorly water-soluble drug

The aim of the present investigation was to develop controlled porosity osmotic system for poorly water-soluble drug based on drug in polymer-surfactant layer technology. A poorly water-soluble drug, glipizide (GZ), was selected as the model drug. The technology involved core of the pellets containing osmotic agent coated with drug dispersed in polymer and surfactant layer, finally coated with release-retardant layer with pore former. The optimized drug-layer-coated pellets were evaluated for solubility of GZ at different pH conditions and characterized for amorphous nature of the drug by differential scanning calorimetry and X-ray powder diffractometry. The optimized release-retardant layer pellets were evaluated for in vitro drug release at different pH, hydrodynamic, and osmolality conditions. The optimized drug layer showed improvement in solubility (10 times in pH 1.2, 11 times in pH 4.5, and 21 times in pH 6.8), whereas pellets coated with cellulose acetate (15.0%, w/w, weight gain) with pore former triethyl citrate (10.0%, w/w, of polymer) demonstrated zero-order drug release for 24 h at different pH conditions; moreover, retardation of drug release was observed with increment of osmolality. This system could be a platform technology for controlled delivery of poorly water-soluble drugs.

Hot melt granulation: a facile approach for monolithic osmotic release tablets

The aim of this work was to develop and evaluate an extended release matrix tablet of glipizide (GP), an oral hypoglycemic agent. Matrices of GP were prepared using microcrystalline cellulose Avicel(™) PH 112, sodium chloride (SC) and polyethylene glycol 6000 (PEG). The content of Kollidon SR (KR), hydroxypropyl methylcellulose K4M premium CR grade (HM) and polyethylene oxide WSR 303 (PO) and/or magnesium hydroxide (MH) was varied in different formulations. All the formulations were processed by hot melt granulation technique. GP release was observed to be influenced by the amount of SC and MH present in the core formulation. The matrix tablets were coated with a solution containing combination of cellulose acetate 398.10 (CA) and PEG. The release of GP was observed to be inversely proportional to the weight of the coating membrane. Matrices containing PO in combination with SC and MH (14.28:8.56) showed significantly higher degree of hydration and swelling that was evident in the surface texture as visualized by scanning electron microscopy (SEM). Results of SEM studies confirmed the presence of pores in the semi-permeable coating membrane from where the GP release would have occurred. The release of GP from this formulation was similar to that of the marketed extended release tablet as judged from similarity factor (f2) analysis, which yielded a value of 74.7. The optimized formulation was found to be stable when tested according to long term and accelerated storage conditions of ICH guidelines upto 3 months.

In vitro Evaluation of Novel Sustained Release Microspheres of Glipizide Prepared by the Emulsion Solvent Diffusion-Evaporation Method

The objective of the current investigation is to reduce dosing frequency and improve patient compliance by designing and systematically evaluating sustained release microspheres of Glipizide. An anti-diabetic drug, Glipizide, is delivered through the microparticulate system using ethyl cellulose as the controlled release polymer. Microspheres were developed by the emulsion solvent diffusion-evaporation technique by using the modified ethanol,-dichloromethane co-solvent system. The polymer mixture of ethyl cellulose and Eudragit^® S100 was used in different ratios (1:0, 1:1, 2:3, 1:4 and 0:1) to formulate batches F1 to F5. The resulting microspheres were evaluated for particle size, densities, flow properties, morphology, recovery yield, drug content, and in vitro drug release behavior. The formulated microspheres were discrete, spherical with relatively smooth surface, and with good flow properties. Among different formulations, the fabricated microspheres of batch F3 had shown the optimum percent drug encapsulation of microspheres and the sustained release of the Glipizide for about 12 h. Release pattern of Glipizide from microspheres of batch F3 followed Korsmeyers-peppas model and zero-order release kinetic model. The value of ‘n’ was found to be 0.960, which indicates that the drug release was followed by anomalous (non-fickian) diffusion. The data obtained thus suggest that a microparticulate system can be successfully designed for sustained delivery of Glipizide and to improve dosage form characteristics for easy formulation.

Development and evaluation of controlled porosity osmotic pump for nifedipine and metoprolol combination

Background

A system that can deliver multi-drug at a prolonged rate is very important for the treatment of various chronic diseases such as diabetes, asthma and heart disease. Controlled porosity osmotic pump tablet (CPOP) system was designed to deliver Nifedipine (NP) and Metoprolol (MP) in a controlled manner up to 12 h. It was prepared by incorporating drugs in the core and coated with various types (PVP, PEG-400 and HPMC) and levels (30, 40 and 50% w/w of polymer) of pore former at a weight gain of 8, 12 & 15%.

Results

Formulation variables like type and level of pore former and percent weight gain of membrane was found to affect the drug release from the developed formulations. Drug release was inversely proportional to the membrane weight but directly related to the level of pore former. Burst strength of the exhausted shell was inversely proportional to the level of pore former, but directly affected by the membrane weight. Results of scanning electron microscopy (SEM) studies showed the formation of pores in the membrane from where the drug release occurred. Dissolution models were applied to drug release data in order to establish the mechanism of drug release kinetics. In vitro release kinetics was subjected to superposition method to predict in vivo performance of the developed formulation.

Conclusion

The developed osmotic system is effective in the multi-drug therapy of hypertension by delivering both drugs in a controlled manner.

Formulation and optimization of osmotically controlled release tablets of glipizide: hot melt granulation

Background: The use of water-soluble additives in osmotic release tablets often renders the wet granulation method unsuitable. Hence, it was proposed to investigate the feasibility of preparing granules comprising of osmogen (sodium chloride), alkalizer (sodium carbonate), polyvinyl pyrroidone (Kollidon® K 30) and carboxymethyl cellulose sodium (Cekol® 30000) by a hot melt technique for obtaining sustained release of glipizide from tablets. Materials and methods: Dry powder mixture wetted with Tween™ 80 was sequentially exposed to 45–110°C for obtaining granules. The effect of varying the quantities of osmogen, Cekol 30000 in granules and pore former in the film coating on in vitro release of glipizide was investigated. Results: Glipizide release increased with an increase in the amount of hydrophilic polymer, osmogen and alkalizer and decreased with increase in the thickness of the coating membrane. Zero-order release independent of stirring rate and media pH through 16 h was observed from tablets of the optimized formulation (glipizide osmotic tablet [GOT] 12). The f2 value of 70.2 indicated similarity in release profiles from this formulation and the marketed extended-release tablet. Accelerated tests (ICH guidelines) revealed stability of GOT 12 tablets.

Development and optimization of micro/nanoporous osmotic pump tablets

Micro/nanoporous osmotic pump tablets coated with cellulose acetate containing polyvinylpyrolidone (PVP) as pore formers were fabricated. Propranolol hydrochloride was used as a model drug in this study. Formulation optimization based on USP 31 requirements was conducted following a central composite design using a two-level factorial plan involving two membrane variables (pore former and coating levels). Effect of molecular weight of pore former (PVP K30 and PVP K90) was also evaluated. Responses of drug release to the variables were analyzed using statistical software (MINITAB 14). Scanning electron microscopy and atomic force microscopy showed that the pores formed by PVP. The drug release was dependent on the molecular weight and concentration of PVP and the level of coating. The results showed that acceptable 12-h profile could be achieved with only specific range of PVP K30-containing membrane at the defined membrane thickness. However, satisfactory 24-h profile could be accomplished by both PVP K30 and PVP K90-containing membrane at the range and membrane thickness tested. Preparation and testing of the optimized formulation showed a good correlation between predicted and observed values.

Design and evaluation of osmotic pump-based controlled release system of Ambroxol Hydrochloride

The purpose of the present study was to design and evaluate an osmotic pump-based drug delivery system for controlling the release of Ambroxol Hydrochloride (Amb). Citric acid, lactose and polyethylene glycol 6000 (PEG 6000) were employed as osmotic agents. Surelease EC containing polyethylene glycol 400 (PEG 400) controlling the membrane porosity was used as semi-permeable membrane. The formulation of tablet core was optimized by orthogonal design and evaluated by weighted mark method. The influences of the amount of PEG 400 and membrane thickness on Amb release were investigated. The optimal osmotic pump tablet (OPT) was evaluated in different release media and at different stirring rates. The major release power confirmed was osmotic pressure. The release of Amb from OPT was verified at a rate of approximately zero-order, and cumulative release percentage at 12?h was 92.6%. The relative bioavailability of Amb OPT in rabbits relative to the commercial sustained capsule was 109.6%. Our results showed that Amb OPT could be a practical preparation with a good prospect.

Design of a 24-hour controlled porosity osmotic pump system containing PVP: formulation variables

PURPOSE

The purpose of this study was to design a 24-hour controlled porosity osmotic pump system that utilizes polyvinyl pyrrolidone (PVP) as an osmotic-suspending/release retarding agent of drugs.

METHODS

Osmotic tablet cores containing various ratios of ketoprofen and PVP were prepared by wet granulation and initially spray coated with similar solution of cellulose acetate. A formulation containing ketoprofen and PVP at a ratio of 1:7 was selected for further studies.

RESULTS

The final formulation containing PVP K-30 in the tablet core augmented the release of ketoprofen (poorly water-soluble) up to 90 % over 24 hours much higher than either PVP K-25 or PVP K-90 and retarded the release of pseudoephedrine HCl (highly water-soluble) up to 18 hours.

CONCLUSION

This study proposed the dual use of PVP in osmotic pump systems containing solids to modulate the release of either poorly or highly water-soluble drug.

Preparation and evaluation of a novel delayed-onset sustained-release system of propranolol hydrochloride

The objective of this work was to prepare and evaluate a new delayed-onset sustained-release system, comprising a sustained-release core tablet with hydroxypropyl methylcellulose as polymer matrix and an ethylcellulose/Eudragit L coating capable of delaying the drug release. The sustained core containing propranolol hydrochloride as the model drug was prepared by granulate tableting and the polymer coating was applied in a computer-controlled coating pan. The dissolution tests demonstrated that the in-vitro drug release was pH-dependent with sufficient gastric resistance, and the lag time (t10%) could be controlled by adjusting the coating level. Three dosage forms including commercial tablet, sustained-release tablet and the delayed-onset sustained-release tablet were administrated to six beagle dogs and the plasma levels of propranolol hydrochloride were measured with high-performance liquid chromatography. The delayed-onset sustained-release tablet had a lag time of 3.0 h in-vitro and 3.5 h in-vivo, and a tmax of 7.0 h. The relative bioavailability for delayed-onset sustained-release tablet was 96.98% compared with commercial tablets. The results indicate that the new propranolol delayed-onset sustained-release system could achieve a relatively constant drug release followed by a programmed lag time, and this may provide a promising drug delivery form for chronopharmacotherapy of certain cardiovascular diseases.

Solid Carriers for Improved Solubility of Glipizide in Osmotically Controlled Oral Drug Delivery System

The purpose of this study was to increase the solubility of glipizide (gli) by solid dispersions SDs technique with polyvinylpyrrolidone (PVP) in aqueous media. The gli-PVP solid dispersion systems was prepared by physical mixing or spray drying method, and characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD) analysis, Fourier transformation-infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The elementary osmotic pumps (EOPs) were prepared with gli-PVP complex and the effect of the PVP percentages on the enhancing of gli dissolution rate was studied. The influences of various parameters e.g., drug- PVP ratio, level of solubility modifier, coating weight gain and diameter of drug releasing orifice on drug release profiles were also investigated. The solubility and dissolution rates of gli were significantly increased by solid dispersion using spray dried method as well as their physical mixture. The obtained results indicated that gli-PVP solid dispersion system has suitable solubility behavior in EOP tablets.

A controlled porosity osmotic pump system with biphasic release of theophylline

A controlled porosity osmotic pump system with biphasic release of theophylline was developed for the nocturnal therapy of asthma. The developed system was composed of a tablet-in-tablet (TNT) core and a controlled porosity coating membrane. Release pattern of the developed system was influenced by amount of pore former (18.2-45.5%, w/w of polymer), weight gain (16-26 mg per tablet) of the coating membrane and osmotic agents used in inner layer of the TNT core. When sodium phosphate and sodium chloride were selected as the osmotic agents in inner and outer layer of the TNT core respectively, target release profile was obtained with coating solution cellulose acetate-polyethylene glycol 400-diethyl phthalate (54.5-36.4-9.1%, w/w) at a weight gain of 16-22 mg per tablet. To examine the mechanism of drug release, release profiles of osmotic agents, micro-environmental osmotic pressure and micro-environmental pH of the formulation during dissolution were studied. Micro-environmental osmotic pressure decreased and micro-environmental pH increased continuously during the whole dissolution process, theophylline release was dominated by the successive dissolution of sodium chloride and sodium phosphate. Theophylline solubility increased as environmental pH exceeded 10.8. At the last stage of the biphasic release, micro-environmental pH in the developed formulation reached 10.9, and theophylline release was promoted by its elevated solubility despite of the decrease of micro-environmental osmotic pressure in the developed formulaiton.

Design and statistical optimization of glipizide loaded lipospheres using response surface methodology

A 32 factorial design was employed to produce glipizide lipospheres by the emulsification phase separation technique using paraffin wax and stearic acid as retardants. The effect of critical formulation variables, namely levels of paraffin wax (X1) and proportion of stearic acid in the wax (X2) on geometric mean diameter (dg), percent encapsulation efficiency (% EE), release at the end of 12 h (rel12) and time taken for 50% of drug release (t50), were evaluated using the F-test. Mathematical models containing only the significant terms were generated for each response parameter using the multiple linear regression analysis (MLRA) and analysis of variance (ANOVA). Both formulation variables studied exerted a significant influence (p < 0.05) on the response parameters. Numerical optimization using the desirability approach was employed to develop an optimized formulation by setting constraints on the dependent and independent variables. The experimental values of dg, % EE, rel12 and t50 values for the optimized formulation were found to be 57.54 +/- 1.38 mum, 86.28 +/- 1.32%, 77.23 +/- 2.78% and 5.60 +/- 0.32 h, respectively, which were in close agreement with those predicted by the mathematical models. The drug release from lipospheres followed first-order kinetics and was characterized by the Higuchi diffusion model. The optimized liposphere formulation developed was found to produce sustained anti-diabetic activity following oral administration in rats.

In vitro and in vivo evaluation of two extended release preparations of combination metformin and glipizide

A system that can deliver multi-drugs at a prolonged rate is very important to the treatment of various chronic diseases such as diabetes, asthma, and heart disease. Two controlled-release systems, which exhibited similar release profiles of metformin and glipizide, i.e., elementary osmotic pump tablets (EOP) and bilayer hydrophilic matrix tablet (BT), were designed. The effects of pH and hydrodynamic conditions on drug release from two formulations were investigated. It was found that both drug releases from EOP were not sensitive to dissolution media pH and hydrodynamics change, while the release of glipizide from BT was influenced by the stirring rate. Moreover, in vivo evaluation was performed, relative to the equivalent dose of conventional metformin tablet and glipizide tablet, by a three-crossover study in six Beagle dogs. Cumulative percent input in vivo was compared to in vitro release profiles. The linear correlations of metformin and glipizide between fraction absorbed in vivo and fraction dissolved in vitro were established for EOP-a true zero-order release formula, whereas only nonlinear correlations were obtained for BT. In conclusion, drug release from EOP was both independent of in vitro and in vivo conditions, where the best sustained release effect was achieved, whereas the in vitro dissolution test employed for BT needed to be further optimized to be biorelevant.

Selection of excipients for extended release formulations of glipizide through drug–excipient compatibility testing

For the development of extended release formulations of glipizide, techniques of thermal and isothermal stress testing (IST) were used to assess the compatibility of glipizide with selected excipients. Initially, differential scanning calorimeter (DSC) was used to evaluate the compatibility. IR spectrum of drug-excipient mixture was also compared with that of pure drug and excipient. Compatibility of excipients defined in the prototype formula was tested using IST. Based on the DSC results alone, magnesium stearate, meglumine, TRIS buffer, and lactose, were found to exhibit interaction with glipizide. Stressed binary mixtures (stored at 50 degrees C for 3 weeks) of glipizide and meglumine showed yellow coloration indicating potential incompatibility. Based on the results of DSC, IR, and/or HPLC, excipients defined in the prototype formula were found to be compatible with glipizide. The optimized formulation developed using the compatible excipients were found to be stable after 3 months of accelerated stability studies (40 degrees C and 75% RH). Overall, compatibility of excipients with glipizide was successfully evaluated using the combination of thermal and IST methods and the formulations developed using the compatible excipients was found to be stable.