Time-release compression-coated core tablet containing nifedipine for chronopharmacotherapy

Oral Drug Delivery Systems Applied to Launched Products: Value for the Patients and Industrial Considerations

Drug delivery systems (DDS) control the amount, rate, and site of administration of drug substances in the body as well as their release and ADME (absorption, distribution, metabolism, excretion). Among the various types of DDS, amount-controlled DDS for solubilization and absorption increase the bioavailability. Time- and amount-controlled DDS are controlled release formulations classified as (1) membrane-type, (2) matrix-type, (3) osmotic-type, and (4) ion-exchange type. Timed-release formulations also control the time and amount of release and the absorption of drugs. Site- and amount-controlled DDS are characterized by colonic delivery and intestinal lymph-targeting to improve release and ADME of drug substances. Finally, site-, time-, and amount-controlled DDS are gastroretentive formulations and local delivery in the oral cavity to improve site retention, release, and ADME of drugs. DDS can enhance efficacy, reduce adverse effects, and optimize the dosing frequency of various drug products to increase patient value. This review focuses on patient value and industrial considerations of launched oral DDS. We provide a technological overview of candidate and marketed DDS, as well as the pros/cons of the technologies for industrialization with consideration to excipients, manufacturing, and storage stability. Moreover, to demonstrate the usefulness of the technology and support the selection and development of the best technologies for patients, we also describe patient value from clinical studies and analyses, particularly with regard to increased new medical options, higher efficacy, reduced adverse effects, reduced number of doses and clinic visits, easier administration, higher quality of life, greater adherence, and satisfaction.

Effect of the compaction parameters on the final structure and properties of a press-coated tablet (Tab-in-Tab): Experimental and numerical study of the influence of core and shell dimensions

With increasing interest in chronopharmaceutics, press-coated tablets have become a key technology in the field of modified release drug delivery systems. Although their benefits in terms of drug release have been largely studied, the comprehension of the compaction process of press-coated tablets is yet to complete. Particularly, the effects of geometrical parameters like the ratios between the thickness/diameter of the core and the thickness/diameter of the whole tablet were so far not much considered. Moreover, there is only few studies in the literature about the effect of the press-coating compression on the final structure and properties of the core. The present work consists in a joint experimental and numerical study that aims to assess these points. The study revealed high stress concentrations on the core during compression, causing high permanent deformations of the core, especially when the ratio between the core thickness and the total tablet thickness was high. The mechanical properties of the core tablet were also shown to be impacted: its density and strength were found to decrease before increasing again along the coating-compression. This effect was highlighted to be dependent on the triaxiality of the stress state (i.e. the ratio between the stresses in the different directions), itself depending on the two studied geometrical parameters. As the properties of the core affect the release attributes, ratios between the dimensions of the core and the dimensions of the whole tablet (thickness, diameter) should be taken into account as critical parameters for the manufacture of press-coated tablets.

Effect of polymer concentration and solution pH on viscosity affecting integrity of a polysaccharide coat of compression coated tablets

Tablets, compression coated with certain polysaccharides and intended for colon delivery, retain the integrity of the coat for an initial period of about 6 h (lag period) beyond which (post-lag period) the coat is degraded by colonic enzymes to induce drug release. This work was undertaken to investigate the factors which influence the integrity of the coat during the lag period. Core tablets containing two model drugs were compression coated with various amounts of carboxymethyl locust bean gum (CMLBG). In-vitro release of drugs, erosion of coat, and steady shear viscosity of CMLBG solutions having different concentrations and solution pH were determined. The viscosity of CMLBG that depended primarily on CMLBG concentration and partly on solution pH was responsible for erosion and integrity of the coat in the lag period. Evaluation of polymer viscosity could describe the integrity of coat of a polysaccharide coated tablet in the lag period.

Formulation and evaluation of time-controlled triple-concentric mefenamic acid tablets for rheumatoid arthritis

A triple-concentric time-controlled release mefenamic acid (MA) tablet was developed using Carbopol and Ethocel polymers. The burst dose was programed to release immediately after an ingestion of tablet to be followed by a lag period of 2-4 h, and thereafter an 8 h controlled release of MA from core tablet. Core tablets were prepared using Carbopols 971P, 974P, 71G or 907 at various concentrations. The core tablet provided a controlled release of MA and the release rate decreased with increasing polymer concentration. Highly cross-linked Carbopol 974P released MA at a faster rate compared to release from Carbopol 971P with medium degree of cross-linking. Carbopols 71G and 971P exhibited essentially similar release rates. Carbopol 907, a linear polymer, showed fastest release of MA. The extent of uptake of dissolution medium by core tablets was inversely related to the rate of release of MA from the tablets. Compression coating of core tablet with Ethocel provided the lag period to delay release of MA from core tablet. Increase in lateral coating thickness decreased MA release and increased lag period. Compression forces applied during compression coating with Ethocel for lag period, and immediate-release MA coating for burst release did not affect the integrity of core tablet.

pH- and ion-sensitive polymers for drug delivery

INTRODUCTION

Drug delivery systems (DDSs) are important for effective, safe, and convenient administration of drugs. pH- and ion-responsive polymers have been widely employed in DDS for site-specific drug release due to their abilities to exploit specific pH- or ion-gradients in the human body.

AREAS COVERED

Having pH-sensitivity, cationic polymers can mask the taste of drugs and release drugs in the stomach by responding to gastric low pH. Anionic polymers responsive to intestinal high pH are used for preventing gastric degradation of drug, colon drug delivery and achieving high bioavailability of weak basic drugs. Tumor-targeted DDSs have been developed based on polymers with imidazole groups or poly(β-amino ester) responsive to tumoral low pH. Polymers with pH-sensitive chemical linkages, such as hydrazone, acetal, ortho ester and vinyl ester, pH-sensitive cell-penetrating peptides and cationic polymers undergoing pH-dependent protonation have been studied to utilize the pH gradient along the endocytic pathway for intracellular drug delivery. As ion-sensitive polymers, ion-exchange resins are frequently used for taste-masking, counterion-responsive drug release and sustained drug release. Polymers responding to ions in the saliva and gastrointestinal fluids are also used for controlled drug release in oral drug formulations.

EXPERT OPINION

Stimuli-responsive DDSs are important for achieving site-specific and controlled drug release; however, intraindividual, interindividual and intercellular variations of pH should be considered when designing DDSs or drug products. Combination of polymers and other components, and deeper understanding of human physiology are important for development of pH- and ion-sensitive polymeric DDS products for patients.

On-off pulsed oral drug-delivery systems: a possible tool for drug delivery in chronotherapy

Circadian rhythms regulate most body functions and are important factors to consider when administering drugs. The existence of circadian rhythms in nature and their influences on human biological systems have given rise to the concept of chronotherapy, which is the science of delivering drugs in a synchronized manner with the rhythm-dependent circadian variation inherent in the human body. The safety and efficacy of a drug can be improved by matching the peak plasma concentration during a 24 h period of the rhythms. An on-off pulsed (pulsatile or time-controlled) release drug-delivery system offers rapid and transient release; stepwise release; and the sustained release of a certain amount of drug within a short time period after a predetermined off-release period according to the circadian rhythm of disease states. These systems deliver the drug at the right time and at an appropriate dosage and are the best approach for chronotherapy. These systems show promise for the optimal therapy of chronic diseases such as asthma, hypertension, myocardial infarction and arthritis, which show a circadian dependency. Various technologies have been adopted to mimic circadian rhythms in physiological functions and diseases. This review focuses on the basic concept of circadian rhythm, chronotherapy and recent advances in the development of on-off pulsed oral drug-delivery systems for optimal therapy.

Hollow microspheres for gastroretentive floating- pulsatile drug delivery: preparation and in vitro evaluation

PURPOSE

A multiparticular floating-pulsatile drug delivery system was developed for time and site specific drug release of piroxicam. A blend of floating and pulsatile principles of drug delivery system would have the advantage that a drug can be released in the upper GI tract after a definite time period.

METHODS

Hollow microspheres were prepared by the emulsion solvent diffusion method using Eudragit S as an enteric acrylic polymer with piroxicam at various polymer/drug ratios in a mixture of dichloromethane and ethanol. Developed formulations were evaluated for yield, encapsulation efficiency, particle size, shape, apparent density, buoyancy studies and dissolution studies.

RESULTS

The obtained microballoons were spherical with no major surface irregularity and mean particle size ranging from 250 to 380 for different batches. Formulations show a slight amount of relaese ranging from 0.7 to 11% in acidic medium (SGF) with complete release of drug in simulated intestinal fluid (SIF) in less than 3 h. Encapsulation efficiency of different formulations varied from 90 to 98%. The optimum loading amount of drug in the particles was found to impart suitable floatable properties to the microballoons. With increasing polymer/drug ratio, buancy of the microballoons increases accompanied by simultaneous reduction of apparent particle density.

CONCLUSION

A pulsatile release of piroxicam was demonstrated by a simple drug delivery system which could be useful in chronopharmacotherapy of rheumatoid arthritis.

In vitro and in vivo evaluation of multilayered pastilles for chronotherapeutic management of nocturnal asthma

OBJECTIVE

The present work was undertaken with an objective to design a multilayered dosage form of doxofylline, using pastillation technology, for the chronotherapeutic management of nocturnal asthma.

RESEARCH DESIGN & METHODS

Pastilles consisting of the drug, polyethylene glycol and colloidal silicon dioxide, were generated using an in-house laboratory-scale pastillation device. The pastilles were further coated with enteric polymers and a floating layer, using conventional coater. The pastilles were subjected to physicochemical analysis, morphological characterization, in vitro drug release studies and in vivo pharmacokinetic studies in rats.

RESULTS

It was observed that colloidal silicon dioxide was instrumental in improving the contact angle of the pastilles. The uncoated pastilles released the drug immediately, while the enteric-coated (10% w/w) pastilles were found to have sufficient acid resistance when the coat is applied with 5% (v/v) triethyl citrate as plasticizer. The in vivo blood serum profile indicated that the pastilles coated with the enteric coat and the additional floating coat were effective in significantly delaying the in vivo drug release required for the chronotherapeutic treatment of nocturnal asthma.

CONCLUSION

The present work opens a new alternative to the conventional tablet or capsule dosage form for the development of both immediate-release and modified-release drug delivery systems.

Development and evaluation of a chronotherapeutic drug delivery system of torsemide

The objective of this study was to prepare and evaluate chronotherapeutic drug delivery systems (ChrDDs) of torsemide. Compression coated tablets (CCT) containing torsemide in the core tablet were prepared by the compression coating technique with different grades of polyethylene oxide (PEO WSR 301 & 1105). The optimized formulations were characterised for tabletting parameters and drug polymer interaction by Fourier-Transform Infrared Spectroscopy (FTIR).The hardness of all the CCT using PEO WSR 301 & PEO WSR 1105 were in the range 6-8 kg/cm² & 5.5 to 7 kg/cm² respectively. Their friability values were <0.3%. All the CCT showed a clear lag time but finalized as per the predetermined lag time. As the amount of PEO was increased in the outer layer the drug released was delayed. The drug content of all the CCT was >99%. The FTIR studies showed no interaction throughout the process of development. Formulations of F7 and of P7 were considered optimized formulations since they yielded a predetermined lag time of 6h before burst release. Hence, these formulations can be exploited to achieve chronotherapeutic drug delivery systems of Torsemide for the treatment of hypertension at the time the patient needs it.

The reality of in-line tablet coating

The possibility of continuous processing in pharmaceutical tablet manufacturing is hampered by the viscoelastic recovery of tablets post-compaction. Compacted tablets are typically aged before coating to allow complete viscoelastic recovery so as to avoid subsequent coating defects. There has been little attempt to overcome tablet recovery in order to enable continuous processing and improve manufacturing efficiency. However, with the introduction of improved or newly developed types of tablet-coating equipment, there is renewed interest in the coating of tablets in-line. In-line tablet coating is defined as the coating of tablets immediately after compaction. It is a one-step highly integrated system that circumvents the delay in processing time typically given to allow viscoelastic recovery of tablets. This review aims to summarize the requirements of an in-line tablet-coating system. The possibility of carrying out in-line tablet coating in the near future will also be discussed.

Optimization of process parameters for a quasi-continuous tablet coating system using design of experiments

The aim of this study was to identify and optimize the critical process parameters of the newly developed Supercell quasi-continuous coater for optimal tablet coat quality. Design of experiments, aided by multivariate analysis techniques, was used to quantify the effects of various coating process conditions and their interactions on the quality of film-coated tablets. The process parameters varied included batch size, inlet temperature, atomizing pressure, plenum pressure, spray rate and coating level. An initial screening stage was carried out using a 2(6-1(IV)) fractional factorial design. Following these preliminary experiments, optimization study was carried out using the Box-Behnken design. Main response variables measured included drug-loading efficiency, coat thickness variation, and the extent of tablet damage. Apparent optimum conditions were determined by using response surface plots. The process parameters exerted various effects on the different response variables. Hence, trade-offs between individual optima were necessary to obtain the best compromised set of conditions. The adequacy of the optimized process conditions in meeting the combined goals for all responses was indicated by the composite desirability value. By using response surface methodology and optimization, coating conditions which produced coated tablets of high drug-loading efficiency, low incidences of tablet damage and low coat thickness variation were defined. Optimal conditions were found to vary over a large spectrum when different responses were considered. Changes in processing parameters across the design space did not result in drastic changes to coat quality, thereby demonstrating robustness in the Supercell coating process.

Predictable pulsatile release of tramadol hydrochloride for chronotherapeutics of arthritis

The present investigation deals with the development of a pH and time-dependent press-coated pulsatile drug delivery system for delivering drugs into the colon. The system consists of a drug containing core, coated by a combination of natural polymer Delonix regia gum (DRG) and hydroxypropyl methylcellulose (HPMC K4M) in various proportions, which controls the onset of release. The whole system was coated with methacrylic acid copolymers, which not only prevents the drug release in the stomach, but also prolongs the lag time. Tramadol HCl was used as a model drug and varying combinations of DRG and HPMC K4M were used to achieve the desired lag time before rapid and complete release of the drug in the colon. It was observed that the lag time depends on the coating ratio of DRG to HPMC and also on press coating weight. Drug release was found to be increased by 15-30% in the presence of colonic microbial flora. The results showed the capability of the system in achieving pulsatile release for a programmable period of time and pH-dependent release to attain colon-targeted delivery.

A new pressure-controlled colon delivery capsule for chronotherapeutic treatment of nocturnal asthma

The purpose of this study was to prepare a pressure-controlled colon delivery capsule (PCDC) containing theophylline (TPH) dispersion in a lipid matrix as a chronotherapeutic drug delivery system for the treatment of nocturnal asthma. The system was made by film coating using Eudragit S100- based formula over the sealed-hard gelatin capsules containing the drug-lipid dispersion. The lipid formula was composed mainly of Gelucire 33/01 (G33) with different ratios of surfactants (1-10%). The efficiency of the prepared system was evaluated in vitro for its ability to withstand both the gastric and intestinal medium. In addition, the drug plasma concentrations were monitored after single administration to Beagle dogs and compared to that obtained after administration of a reference marketed, generic, sustained-release TPH tablets, Avolen(®) SR. It was found that the optimum lipid formula was GL2 containing 90% G33 and 10% Labrasol. The film-coated capsules showed complete resistance to both the acidic environment (pH 1.2) for 2 hours and phosphate buffer pH 6.8 for 3 hours at 37°C. In vivo evaluation of the TPH-based PCDCs showed longer lag time compared TO the marketed formula followed by sudden increase in TPH blood levels, which recommends the high potential of this system as a chronotherapeutic drug delivery for nocturnal asthma. The prepared PCDCs exhibited a significantly higher C(max) and T(max) and a nonsignificantly different AUC compared with Avolen(®) SR. Higher TPH blood levels from 1 to 8 hours postadministration was detected in the case of the prepared PCDCs.

Polymer blends used to prepare nifedipine loaded hollow microspheres for a floating-type oral drug delivery system: in vitro evaluation

The aim of this study was to investigate whether hollow microspheres prepared from polymer blends of polyvinyl pyrrolidone (PVP) and ethyl cellulose (EC) could improve the vitro release behavior of the poorly water-soluble drug nifedipine. Hollow microspheres containing nifedipine were prepared by a solvent diffusion-evaporation method using various ratios of PVP and EC codissolved with drug in ethanol/ether (5:1, v/v). The hollow microspheres could float in release medium for more than 24 h, and floating capacities were not be influenced by mixing PVP. In vitro release profiles of hollow microspheres prepared using EC along showed an initial burst release to some extent, and the cumulative release percentage was less than 55% after 24 h. But, not only the slope but also the shape of the release curves was affected by using mixture of PVP and EC. What's more important, when the ratio (PVP/EC) increased to 1.5:8.5, the cumulative release percentage could be increased to 95.8%. Furthermore, the release rate of microspheres showed a zero order approximate dynamic model and could be expressed by the following equation: Q=3.78t+8.52 (r=0.990). Consequently, hollow microspheres prepared using polymer blends of PVP and EC (1.5:8.5, w/w) could be suitable for floating-type controlled-release delivery systems for the oral administration of nifedipine.

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.

The Influence of Surfactants and Additives on Drug Release from a Cationic Eudragit Coated Multiparticulate Diltiazem Formulation

A cationic polymethacrylate coated multiparticulate diltiazem formulation exhibited sigmoidal drug release. Lag time prior to drug release was influenced by dissolution media, coat thickness, and by the nature of additives included in the formulation. Incorporation of up to 5% w/w sodium lauryl sulfate (SLS) in the coating membrane resulted in substantial increases in lag times in acidic and neutral media. The extent of drug release in acid was 100%, whereas in phosphate buffer, the extent of release was dependent on the level of SLS. Substituting SLS for various compounds was used to assess the functionality of the SLS molecule responsible for these behaviors. The ability to ion-pair with the polymer and the presence of a hydrophobic moiety were both important functionalities.

Solventless pharmaceutical coating processes: a review

Coatings are an essential part in the formulation of pharmaceutical dosage form to achieve superior aesthetic quality (e.g., color, texture, mouth feel, and taste masking), physical and chemical protection for the drugs in the dosage forms, and modification of drug release characteristics. Most film coatings are applied as aqueous- or organic-based polymer solutions. Both organic and aqueous film coating bring their own disadvantages. Solventless coating technologies can overcome many of the disadvantages associated with the use of solvents (e.g., solvent exposure, solvent disposal, and residual solvent in product) in pharmaceutical coating. Solventless processing reduces the overall cost by eliminating the tedious and expensive processes of solvent disposal/treatment. In addition, it can significantly reduce the processing time because there is no drying/evaporation step. These environment-friendly processes are performed without any heat in most cases (except hot-melt coating) and thus can provide an alternative technology to coat temperature-sensitive drugs. This review discusses and compares six solventless coating methods - compression coating, hot-melt coating, supercritical fluid spray coating, electrostatic coating, dry powder coating, and photocurable coating - that can be used to coat the pharmaceutical dosage forms.

Design and Gamma-Scintigraphic Evaluation of a Floating and Pulsatile Drug Delivery System Based on an Impermeable Cylinder

A blend of floating and pulsatile principles of drug delivery system seems to present the advantage that a drug can be released in the upper GI tract after a definite time period of no drug release. The objective of this study was to develop and evaluate a floating and pulsatile drug delivery system based on an impermeable cylinder. Pulsatile capsule was prepared by sealing the drug tablet and the buoyant material filler inside the impermeable capsule body with erodible plug. The drug delivery system showed typical floating and pulsatile release profile with a lag time followed by a rapid release phase. The lag time prior to the pulsatile drug release correlated well with the erosion properties of plugs and the composition of the plug could be controlled by the weight of the plug. The buoyancy of the whole system depended on the bulk density of the dosage form. Gamma-scintigraphic evaluation in humans was used to establish methodology capable of showing the subsequent in vivo performance of the floating and pulsatile release capsule. Developed formulations showed instantaneous floating with no drug release during the lag time followed by a pulse drug release. From the gamma-scintigraphic results, the pulsatile release capsule we prepared could achieve a rapid release after lag time in vivo, which was longer than that in vitro. The scintigraphic evaluation could confirm qualitatively that the system with in vitro lag time of 4.0 h provided, with relatively high reproducibility, a pulsatile release occurred around 5.0 h after administration.