Chronopharmaceutical drug delivery from a pulsatile capsule device based on programmable erosion

The importance of surface composition and wettability on the dissolution performance of high drug loading amorphous dispersion formulations

One of the limitations with an amorphous solid dispersion (ASD) formulation strategy is low drug loading. Hydrophobic drugs have poor wettability and require a substantial amount of polymer to stabilize the amorphous drug and facilitate release. Using grazoprevir and hypromellose acetate succinate as model drug and polymer, respectively, the interplay between particle surface composition, particle wettability, and release performance was investigated. A hierarchical particle approach was used where the surfaces of high drug loading ASDs generated by either solvent evaporation or co-precipitation were further modified with a secondary excipient (i.e., polymer or wetting agent). The surface-modified particles were characterized for drug release, wettability, morphology, and surface composition using two-stage dissolution studies, contact angle measurements, scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. Despite surface modification with hydrophilic polymers, the hierarchical particles did not consistently exhibit good release performance. Contact angle measurements showed that the secondary excipient had a profound impact on particle wettability. Particles with good wettability showed improved drug release relative to particles that did not wet well, even with similar drug loadings. These observations underscore the intricate interplay between particle wettability and performance in amorphous dispersion formulations and illustrate a promising hierarchical particle approach to formulate high drug loading amorphous dispersions with improved dissolution performance.

Hypromellose - A traditional pharmaceutical excipient with modern applications in oral and oromucosal drug delivery

Hydroxypropylmethylcellulose (HPMC), also known as Hypromellose, is a traditional pharmaceutical excipient widely exploited in oral sustained drug release matrix systems. The choice of numerous viscosity grades and molecular weights available from different manufacturers provides a great variability in its physical-chemical properties and is a basis for its broad successful application in pharmaceutical research, development, and manufacturing. The excellent mucoadhesive properties of HPMC predetermine its use in oromucosal delivery systems including mucoadhesive tablets and films. HPMC also possesses desirable properties for formulating amorphous solid dispersions increasing the oral bioavailability of poorly soluble drugs. Printability and electrospinnability of HPMC are promising features for its application in 3D printed drug products and nanofiber-based drug delivery systems. Nanoparticle-based formulations are extensively explored as antigen and protein carriers for the formulation of oral vaccines, and oral delivery of biologicals including insulin, respectively. HPMC, being a traditional pharmaceutical excipient, has an irreplaceable role in the development of new pharmaceutical technologies, and new drug products leading to continuous manufacturing processes, and personalized medicine. This review firstly provides information on the physical-chemical properties of HPMC and a comprehensive overview of its application in traditional oral drug formulations. Secondly, this review focuses on the application of HPMC in modern pharmaceutical technologies including spray drying, hot-melt extrusion, 3D printing, nanoprecipitation and electrospinning leading to the formulation of printlets, nanoparticle-, microparticle-, and nanofiber-based delivery systems for oral and oromucosal application. Hypromellose is an excellent excipient for formulation of classical dosage forms and advanced drug delivery systems. New methods of hypromellose processing include spray draying, hot-melt extrusion, 3D printing, and electrospinning.

Bilayer Tablet Based Chronotherapeutics in the Management of Nocturnal Asthma: An Overview

BACKGROUND

Asthma is a common ailment with a larger circadian difference. Nocturnal Asthma (NA) is an inconstant exacerbation of asthmatic condition related to the rise in warning sign during the night time and there is a need for its treatment addressing air route alertness and decline in lung functions. These symptoms are linked to sleep or known as circadian events. Chronotherapeutics is a management system based on an in-vivo drug accessibility programmed to check the rhythms of ailment in a direction to improve the therapeutic outcomes by suppressing the side effects. This review aims to provide an overview of NA, chronotherapeutics for the treatment of NA, bilayer tablets, and advanced techniques involved in the fabrication of bilayer tablets. The review also discusses some of the related patents.

METHODS

Relevant literature about the latest developments and updated information related to NA, chronotherapeutics and bilayer tablets has been very widely searched on different biomedical literature programs such as Google, Web of Science, PubMed portals, etc. Bilayer tablet mediated chronotherapy has gained significant attention and consideration as it is developed and fabricated based on the body's circadian rhythm. Bilayer tablets can deliver the bioactive compounds at an appropriate time, place as well as amount and site.

RESULTS

Available literature advocated that the bilayer matrix tablet containing a single drug in the sustained release film and fast releasing film, may be beneficial for the chronic diseases like asthma, migraine, diabetes, hypertension and inflammation which usually require immediate as well as maintained therapeutic effect.

CONCLUSION

The application of nanotechnology in the arena of medicine will transform the diagnosis and treatment strategies of a wide range of diseases in the upcoming years. The findings of this review confirm the importance of bilayer tablet based chronotherapy in nocturnal asthma.

A Three-Pulse Release Tablet for Amoxicillin: Preparation, Pharmacokinetic Study and Physiologically Based Pharmacokinetic Modeling

BACKGROUND

Amoxicillin is a commonly used antibiotic which has a short half-life in human. The frequent administration of amoxicillin is often required to keep the plasma drug level in an effective range. The short dosing interval of amoxicillin could also cause some side effects and drug resistance, and impair its therapeutic efficacy and patients' compliance. Therefore, a three-pulse release tablet of amoxicillin is desired to generate sustained release in vivo, and thus to avoid the above mentioned disadvantages.

METHODS

The pulsatile release tablet consists of three pulsatile components: one immediate-release granule and two delayed release pellets, all containing amoxicillin. The preparation of a pulsatile release tablet of amoxicillin mainly includes wet granulation craft, extrusion/spheronization craft, pellet coating craft, mixing craft, tablet compression craft and film coating craft. Box-Behnken design, Scanning Electron Microscope and in vitro drug release test were used to help the optimization of formulations. A crossover pharmacokinetic study was performed to compare the pharmacokinetic profile of our in-house pulsatile tablet with that of commercial immediate release tablet. The pharmacokinetic profile of this pulse formulation was simulated by physiologically based pharmacokinetic (PBPK) model with the help of Simcyp®.

RESULTS AND DISCUSSION

Single factor experiments identify four important factors of the formulation, namely, coating weight of Eudragit L30 D-55 (X1), coating weight of AQOAT AS-HF (X2), the extrusion screen aperture (X3) and compression forces (X4). The interrelations of the four factors were uncovered by a Box-Behnken design to help to determine the optimal formulation. The immediate-release granule, two delayed release pellets, together with other excipients, namely, Avicel PH 102, colloidal silicon dioxide, polyplasdone and magnesium stearate were mixed, and compressed into tablets, which was subsequently coated with Opadry® film to produce pulsatile tablet of amoxicillin. In vitro release study firstly indicated a three-pulse release profile of the tablet. Later the pulse tablet was found to generate the sustained release of amoxicillin in beagle dogs. Furthermore, the Simcyp® software was used to simulate the in vivo concentration time curve model of the three-pulse release tablet for amoxicillin in both human and beagle dog. The prediction by PBPK model nicely fitted the observation in human and beagle dog.

CONCLUSIONS

This study has demonstrated the interrelation of factors affecting the pulsatile formulation of amoxicillin using a Box-Behnken design. The three-pulse release tablets of amoxicillin were proven to generate pulsatile release in vitro and sustained release in vivo. This formulation was also found to extend the effective plasma concentration in human compared to the tablet of immediate release based on the simulation data by PBPK modeling. This study provides an example of using PBPK to guide the development of pulsatile dosage forms.

G. S. Design and development of a dual-drug loaded pulsatile capsule for treatment of hypertension – in vitro and ex vivo studies

The aim of the present study was to design and evaluate a pulsatile dosage form to program the release of dual antihypertensive drugs to mimic the circadian pattern of BP.

Patented pulsatile drug delivery technologies for chronotherapy

INTRODUCTION

Oral-controlled and modified-release drug delivery systems with zero-order sustained-release kinetics have been developed and proven suitable for meeting increasingly sophisticated therapeutic needs. Nevertheless, the impact of basic chronobiology concepts on the practice of medicine is still ongoing and to address chronotherapy needs, various types of pulsatile drug delivery systems have been innovated. The purpose of this review is to highlight these innovations in the field of chronotherapy.

AREAS COVERED

The present review discusses in depth on recent patents and developments related to pulsatile drug delivery systems with eroding, soluble or rupturable barrier coatings, and systems with capsular structures. Besides focusing on all recent innovations, the review addresses the novelty and feasibility of all upcoming technologies being exploited considering pulsatile drug delivery systems.

EXPERT OPINION

There has been a growing interest in pulsatile delivery, which generally refers to the liberation of drugs following a programmable and well-defined lag phase from the time of administration. From 1981 until the present date, patent publications related to pulsatile drug delivery have shown more promising systems with numerous developments in arena of drug delivery. Future development of chronotherapeutic medications requires proper assessment and integration with other emerging disciplines such as hydrogel and transdermal delivery systems. The selection of the appropriate chronopharmaceutical technology should take into considerations with the ease of manufacturing and the cost-effectiveness.

Recent technologies in pulsatile drug delivery systems

Pulsatile drug delivery systems (PDDS) have attracted attraction because of their multiple benefits over conventional dosage forms. They deliver the drug at the right time, at the right site of action and in the right amount, which provides more benefit than conventional dosages and increased patient compliance. These systems are designed according to the circadian rhythm of the body, and the drug is released rapidly and completely as a pulse after a lag time. These products follow the sigmoid release profile characterized by a time period. These systems are beneficial for drugs with chronopharmacological behavior, where nocturnal dosing is required, and for drugs that show the first-pass effect. This review covers methods and marketed technologies that have been developed to achieve pulsatile delivery. Marketed technologies, such as Pulsincap^TM, Diffucaps^®, CODAS^®, OROS^® and PULSYS^TM, follow the above mechanism to render a sigmoidal drug release profile. Diseases wherein PDDS are promising include asthma, peptic ulcers, cardiovascular ailments, arthritis and attention deficit syndrome in children and hypercholesterolemia. Pulsatile drug delivery systems have the potential to bring new developments in the therapy of many diseases.

A review of polymeric refabrication techniques to modify polymer properties for biomedical and drug delivery applications

Polymers are extensively used in the pharmaceutical and medical field because of their unique and phenomenal properties that they display. They are capable of demonstrating drug delivery properties that are smart and novel, such properties that are not achievable by employing the conventional excipients. Appropriately, polymeric refabrication remains at the forefront of process technology development in an endeavor to produce more useful pharmaceutical and medical products because of the multitudes of smart properties that can be attained through the alteration of polymers. Small alterations to a polymer by either addition, subtraction, self-reaction, or cross reaction with other entities have the capability of generating polymers with properties that are at the level to enable the creation of novel pharmaceutical and medical products. Properties such as stimuli-responsiveness, site targeting, and chronotherapeutics are no longer figures of imaginations but have become a reality through utilizing processes of polymer refabrication. This article has sought to review the different techniques that have been employed in polymeric refabrication to produce superior products in the pharmaceutical and medical disciplines. Techniques such as grafting, blending, interpenetrating polymers networks, and synthesis of polymer complexes will be viewed from a pharmaceutical and medical perspective along with their synthetic process required to attain these products. In addition to this, each process will be evaluated according to its salient features, impeding features, and the role they play in improving current medical devices and procedures.

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.

Development of a gastroretentive pulsatile drug delivery platform

Objectives

To develop a novel gastroretentive pulsatile drug delivery platform by combining the advantages of floating dosage forms for the stomach and pulsatile drug delivery systems.

Methods

A gastric fluid impermeable capsule body was used as a vessel to contain one or more drug layer(s) as well as one or more lag-time controlling layer(s). A controlled amount of air was sealed in the innermost portion of the capsule body to reduce the overall density of the drug delivery platform, enabling gastric floatation. An optimal mass fill inside the gastric fluid impermeable capsule body enabled buoyancy in a vertical orientation to provide a constant surface area for controlled erosion of the lag-time controlling layer. The lag-time controlling layer consisted of a swellable polymer, which rapidly formed a gel to seal the mouth of capsule body and act as a barrier to gastric fluid ingress.

Key findings

By varying the composition of the lag-time controlling layer, it was possible to selectively program the onset of the pulsatile delivery of a drug.

Conclusions

This new delivery platform offers a new method of delivery for a variety of suitable drugs targeted in chronopharmaceutical therapy. This strategy could ultimately improve drug efficacy and patient compliance, and reduce harmful side effects by scaling back doses of drug administered.

A two pulse drug delivery system for amoxicillin: an attempt to counter the scourge of bacterial resistance against antibiotics

Bearing in mind the present scenario of the increasing biological tolerance of bacteria against antibiotics, a time controlled two pulse dosage form of amoxicillin was developed. The compression coating inlay tablet approach was used to deliver the drug in two pulses to different parts of the GIT after a well defined lag time between the two releases. This was made possible by formulating a core containing one of the two drug fractions (intended to be delivered as the second pulse), which was spray coated with a suspension of ethyl cellulose and a hydrophilic but water insoluble agent as a pore former (microcrystalline cellulose). Coating of up to 5% (m/m) was applied over the core tablet, giving a corresponding lag of 3, 5, 7 and 12 h. Increasing the level of coating led to retardation of the water uptake capacity of the core, leading to prolongation of the lag time. Microcrystalline cellulose was used as a hydrophilic but water insoluble porosity modifier in the barrier layer, varying the concentration of which had a significant effect on shortening or prolongation of the lag time. This coated system was further partially compression coated with the remaining drug fraction (to be released as the first immediate release pulse) with a disintegrant, giving a final tablet. The core tablet and the final two pulse inlay tablet were further investigated for their in vitro performance.

Pharmaceutically used polymers: principles, structures, and applications of pharmaceutical delivery systems

This chapter presents a general overview of pharmaceutically used polymers with respect to their physicochemical characteristics and factors affecting drug delivery abilities. Pharmaceutical polymers, chemical structure, and properties are discussed for their applications in controlled drug release systems. An additional focus is on new polymers (dendrimers, hyperbranched polymers), considering their chemical versatility, uniqueness, and future implications. Problems associated with controlled drug release systems are also highlighted. Finally, applications of FDA-approved polymers used for oral drug delivery systems are outlined.

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.

Drug delivery technologies for chronotherapeutic applications

It has been proven that the body follows a 24-hour cycle called a circadian rhythm. This cycle is coordinated by the suprachiasmatic nucleus and controls nearly all bodily functions including those related to drug delivery. Knowledge of the body's circadian rhythm leads to an improved understanding of diseases and their treatment, known as chronotherapy, such that synchronizing drug application in accordance with the natural rhythm of the body leads to improved disease management and a greater patient therapeutic outcome. Chronotherapeutic diseases include asthma, cardiovascular diseases, glaucoma, rheumatoid arthritis and cancers. In order to treat these diseases numerous chronotherapeutic drug delivery systems have been developed, such that drug is released in the period when it is most needed. This review paper attempts to concisely explicate the role of circadian rhythms in various disease states and furthermore describes the various oral drug delivery technologies that have been employed for the treatment of chronotherapeutic diseases.

Development and Mathematical Simulation of Theophylline Pulsatile Release Tablets

Theophylline pulsatile release tablets consisting of a fast-swelling core with a water-insoluble ethylcellulose were developed. Effects of coating material, the amount of the plasticizer, subcoating, the type of the disintegrant, and coating level on the release profiles were investigated. Results showed that ethylcellulose was the best candidate polymer for pulsatile release tablets. Rupture time increased with increasing the amount of the plasticizer, but 15% plasticizer provided the best release profiles. Tablets with Methocel E50 as subcoating was most optimal in order to achieve a long lag time and followed by a rapid release. The lag time of tablets containing different disintegrants increased in the following order: croscarmellose (Ac-Di-Sol) < sodium starch glycolate (Explotab) < low-substituted hydroxypropyl cellulose (L-HPC) < crospovidone (Kollidon CL). And the rupture time increased with higher coating level. A mathematical model was presented to predict the lag time prior to rupture. Results of the water uptake experiment were used to estimate the apparent diffusion coefficient of the coating tablets. The prediction of the lag time based on the presented model is in good agreement with the experimental results.

Erosion Characteristics of an Erodible Tablet Incorporated in a Time-Delayed Capsule Device

A time-delayed oral drug delivery device was investigated in which an erodible tablet (ET), sealing the mouth of an insoluble capsule, controlled the lag-time prior to drug release. The time-delayed capsule (TDC) lag-time may be altered by manipulation of the excipients used in the preparation of the ET. Erosion rates and drug release profiles from TDCs were investigated with four different excipient admixtures with lactose: calcium sulphate dihydrate (CSD), dicalcium phosphate (DCP), hydroxypropylmethyl cellulose (HPMC; Methocel K100LV grade) and silicified microcrystalline cellulose (SMCC; Prosolv 90 grade). Additionally, the compressibility of different insoluble coated capsules was tested at different moisture levels to determine their overall integrity and suitability for oral delivery. Erosion rates of CSD, DCP, and SMCC displayed a nonlinear relationship to their concentration, while HPMC indicated rapid first-order erosion followed by zero-order erosion, the onset of which was dependent on the HPMC concentration. Capsule integrity was confirmed to be most suitable for oral delivery when the insoluble ethyl cellulose coat was applied to a hard gelatin capsule using an organic spray coating process. T50% drug release times varied between 245 (+/-33.4) and 393 (+/-40.8) minutes for 8% and 20% DCP, respectively, T50% release times of 91 (+/-22.1) and 167 (+/-34.6) were observed for 8% and 20% CSD; both formulations showed incidence of premature drug release. The SMCC formulations showed high variability due to lamination effects. The HPMC formulations had T50% release times of 69 (+/-13.9), 213 (+/-25.4), and 325 (+/-30.3) minutes for 15%, 24%, and 30% HPMC concentrations respectively, with no premature drug release. In conclusion, HPMC showed the highest reproducibility for a range of time-delayed drug release from the assembled capsule formulation. The method of capsule coating was confirmed to be important by investigation of the overall capsule integrity at elevated humidity levels. The erosion characteristics of ETs containing HPMC may be described by gravimetric loss. The novel time-delayed capsule device presented in this study may be assembled to include an erodible tablet with a known concentration of HPMC. A variety of suitable drugs for targeted chronopharmaceutical therapy can be incorporated into such a device, ultimately improving drug efficacy and patient compliance, and reducing harmful side effects.

Oral pulsatile delivery systems based on swellable hydrophilic polymers

Upon contact with aqueous fluids, swellable hydrophilic polymers undergo typical chain relaxation phenomena that coincide with a glassy-rubbery transition. In the rubbery phase, these polymers may be subject to swelling, dissolution and erosion processes or, alternatively, form an enduring gel barrier when cross-linked networks (hydrogels) are dealt with. Because of the peculiar hydration and biocompatibility properties, such materials are widely exploited in the pharmaceutical field, particularly as far as hydrophilic cellulose derivatives are concerned. In oral delivery, they have for long been employed in the manufacturing of prolonged release matrices and, more recently, for pulsatile (delayed) release devices as well. Pulsatile delivery, which is meant as the liberation of drugs following programmed lag phases, has drawn increasing interest especially in view of emerging chronotherapeutic approaches. In pursuit of pulsatile release, various design strategies have been proposed, chiefly including reservoir, capsular and osmotic formulations. In most cases, water-swellable polymers play a key role in the overall delivery mechanism after being activated by physiological media. Based on these premises, the aim of the present review is to survey the main oral pulsatile delivery systems, for which swelling, dissolution and/or erosion of hydrophilic polymers are primarily involved in the control of release.

In-vitro/in-vivo correlation of pulsatile drug release from press-coated tablet formulations: A pharmacoscintigraphic study in the beagle dog

The aim of the current study was to investigate the in-vitro and in-vivo performance of a press-coated tablet (PCT) intended for time delayed drug release, consisting of a rapidly disintegrating theophylline core tablet, press-coated with barrier granules containing glyceryl behenate (GB) and low-substituted hydroxypropylcellulose (L-HPC). The PCTs showed pulsatile release with a lag time dependent upon the GB and L-HPC composition of the barrier layer. In-vivo gamma-scintigraphic studies were carried out for PCTs containing GB:L-HPC at 65:35 w/w and 75:25 w/w in the barrier layer in four beagle dogs, in either the fed or fasted state. The in-vivo lag time in both the fed and fasted states did not differ significantly (p>0.05) from the in-vitro lag time. Additionally, no significant difference (p<0.05) between in-vivo fed and fasted disintegration times was observed, demonstrating that in-vivo performance of the PCT was not influenced by the presence or absence of food in the gastrointestinal tract. A distinct lag time was obtained prior to the appearance of drug in plasma and correlated (R2=0.98) with disintegration time observed from scintigraphic images. However, following disintegration, no difference in pharmacokinetic parameters (AUC(0-6 dis), K(el), Cmax) was observed. The current study highlighted the potential use of these formulations for chronopharmaceutical drug delivery.

Time-controlled oral delivery systems for colon targeting

In recent years, many research efforts have been spent in the achievement of selective delivery of drugs into the colon following oral administration. Indeed, colonic release is regarded as a beneficial approach to the pharmacological treatment or prevention of widespread large bowel pathologies, such as inflammatory bowel disease and adenocarcinoma. In addition, it is extensively explored as a potential means of enhancing the oral bioavailability of peptides, proteins and other biotechnological molecules, which are known to be less prone to enzymatic degradation in the large, rather than in the small, intestine. Based on these premises, several formulation strategies have been attempted in pursuit of colonic release, chiefly including microflora-, pH-, pressure- and time-dependent delivery technologies. In particular, this review is focused on the main design features and release performances of time-controlled devices, which rely on the relative constancy that is observed in the small intestinal transit time of dosage forms.

Design and evaluation of a dry coated drug delivery system with an impermeable cup, swellable top layer and pulsatile release

In this investigation a novel oral pulsatile drug delivery system based on a core-in-cup dry coated tablet, where the core tablet surrounded on the bottom and circumference wall with inactive material, is proposed. The system consists of three different parts, a core tablet, containing the active ingredient, an impermeable outer shell and a top cover layer-barrier of a soluble polymer. The core contained either diclofenac sodium or ketoprofen as model drugs. The impermeable coating cup consisted of cellulose acetate propionate and the top cover layer of hydrophilic swellable materials, such as polyethylene oxide, sodium alginate or sodium carboxymethyl cellulose. The effect of the core, the polymer characteristics and quantity at the top cover layer, on the lag time and drug release was investigated. The results show that the system release of the drug after a certain lag time generally due to the erosion of the top cover layer. The quantity of the material, its characteristics (viscosity, swelling, gel layer thickness) and the drug solubility was found to modify lag time and drug release. The lag time increased when the quantity of top layer increased, whereas drug release decreased. The use of sodium carboxymethyl cellulose resulted in the greatest swelling, gel thickness and lag time, but the lowest drug release from the system. Polyethylene oxide showed an intermediate behaviour while, the sodium alginate exhibited the smallest swelling, gel thickness and the shortest lag time, but the fastest release. These findings suggest that drug delivery can be controlled by manipulation of these formulations.

Oral pulsatile drug delivery systems

In the field of modified release, there has been a growing interest in pulsatile delivery, which generally refers to the liberation of drugs following a programmable lag phase from the time of administration. In particular, the recent literature reports on a variety of pulsatile release systems intended for the oral route, which have been recognised as potentially beneficial to the chronotherapy of widespread diseases, such as bronchial asthma or angina pectoris, with mainly night or early morning symptoms. In addition, time-dependent colon delivery may also represent an appealing related application. The delayed liberation of orally administered drugs has been achieved through a range of formulation approaches, including single- or multiple-unit systems provided with release-controlling coatings, capsular devices and osmotic pumps. Based on these premises, the aim of this review is to outline the rational and prominent design strategies behind oral pulsatile delivery.

Hydrophilic excipients modulate the time lag of time-controlled disintegrating press-coated tablets

An oral press-coated tablet was developed by means of direct compression to achieve the time-controlled disintegrating or rupturing function with a distinct predetermined lag time. This press-coated tablet containing sodium diclofenac in the inner core was formulated with an outer shell by different weight ratios of hydrophobic polymer of micronized ethylcellulose (EC) powder and hydrophilic excipients such as spray-dried lactose (SDL) or hydroxypropyl methylcellulose (HPMC). The effect of the formulation of an outer shell comprising both hydrophobic polymer and hydrophilic excipients on the time lag of drug release was investigated. The release profile of the press-coated tablet exhibited a time period without drug release (time lag) followed by a rapid and complete release phase, in which the outer shell ruptured or broke into 2 halves. The lag phase was markedly dependent on the weight ratios of EC/SDL or EC/HPMC in the outer shell. Different time lags of the press-coated tablets from 1.0 to 16.3 hours could be modulated by changing the type and amount of the excipients. A semilogarithmic plot of the time lag of the tablet against the weight ratios of EC/SDL or EC/HPMC in the outer shell demonstrated a good linear relationship, with r = 0.976 and r = 0.982, respectively. The predetermined time lag prior to the drug release from a press-coated tablet prepared by using a micronized EC as a retarding coating shell can be adequately scheduled with the addition of hydrophilic excipients according to the time or site requirements.

Chronopharmaceutics: gimmick or clinically relevant approach to drug delivery?

Due to advances in chronobiology, chronopharmacology, and global market constraints, the traditional goal of pharmaceutics (e.g. design drug delivery systems with a constant drug release rate) is becoming obsolete. However, the major bottleneck in the development of drug delivery systems that match the circadian rhythm (chronopharmaceutical drug delivery systems: ChrDDS) may be the availability of appropriate technology. The last decade has witnessed the emergence of ChrDDS against several diseases. The increasing research interest surrounding ChrDDS may lead to the creation of a new sub-discipline in pharmaceutics known as chronopharmaceutics. This review introduces the concept of chronopharmaceutics, addresses theoretical/formal approaches to this sub-discipline, underscores potential disease-targets, revisits existing technologies and examples of ChrDDS. Future development in chronopharmaceutics may be made at the interface of other emerging disciplines such as system biology and nanomedicine. Such novel and more biological approaches to drug delivery may lead to safer and more efficient disease therapy in the future.

The effect of wet granulation on the erosion behaviour of an HPMC–lactose tablet, used as a rate-controlling component in a pulsatile drug delivery capsule formulation

The purpose of this study was to investigate the variability in the performance of a pulsatile capsule delivery system induced by wet granulation of an erodible HPMC tablet, used to seal the contents within an insoluble capsule body. Erodible tablets containing HPMC and lactose were prepared by direct compression (DC) and wet granulation (WG) techniques and used to seal the model drug propranolol inside an insoluble capsule body. Dissolution testing of capsules was performed. Physical characterisation of the tablets and powder blends used to form the tablets was undertaken using a range of experimental techniques. The wet granulations were also examined using the novel technique of microwave dielectric analysis (MDA). WG tablets eroded slower and produced longer lag-times than those prepared by DC, the greatest difference was observed with low concentrations of HPMC. No anomalous physical characteristics were detected with either the tablets or powder blends. MDA indicated water-dipole relaxation times of 2.9, 5.4 and 7.7x10(-8)ms for 15, 24 and 30% HPMC concentrations, respectively, confirming that less free water was available for chain disentanglement at high concentrations. In conclusion, at low HPMC concentrations water mobility is at its greatest during the granulation process, such formulations are therefore more sensitive to processing techniques. Microwave dielectric analysis can be used to predict the degree of polymer spreading in an aqueous system, by determination of the water-dipole relaxation time.

Modulation of combined-release behaviors from a novel “tablets-in-capsule system”

A multifunctional and multiple unit system, which contains versatile mini-tablets in a hard gelation capsule, is developed by preparing Rapid-release Mini-Tablets (RMTs), Sustained-release Mini-Tablets (SMTs), Pulsatile Mini-Tablets (PMTs), and Delayed-onset Sustained-release Mini-Tablets (DSMTs), each with various lag times of release. Based on the combinations of mini-tablets, multiplied pulsatile drug delivery system (DDS), site-specific DDS, slow/quick DDS, quick/slow DDS, and zero-order DDS could be obtained. Velocity-time curve, instead of the cumulative percentage drug release profile, is plotted. The nonlinear least square model fit program is applied to process the velocity data of dissolution. The test curves coincided with the theoretical curves from simple summation of v-t equations of individual mini-tablets. Therefore, the programmed DDS can be predicted by adding the v-t equations of various mini-tablets to calculate the theoretical equations and be implemented.

Development of pulsatile release tablets with swelling and rupturable layers

A tablet system consisting of cores coated with two layers of swelling and rupturable coatings was prepared and evaluated as pulsatile drug delivery system. Cores containing buflomedil HCl as model drug were prepared by direct compression of different ratios of spray-dried lactose and microcrystalline cellulose and were then coated sequentially with an inner swelling layer containing a superdisintegrant (croscarmellose sodium) and an outer rupturable layer of ethylcellulose. The effect of core composition, level of swelling layer and rupturable coating, and magnesium stearate in rupturable layer was investigated. Mechanical properties of ethylcellulose films in the dry and wet state were characterized with a puncture test. Rupture and dissolution tests were performed using the USP XXIV paddle method at 50 rpm in 0.1 N HCl. The lag time of the pulsatile release tablets decreased with increasing amount of microcrystalline cellulose in the cores and increased with increasing levels of both swelling layer and rupturable ethylcellulose coating. Increasing levels of the ethylcellulose coating retarded the water uptake and thus prolonged the lag time. Addition of magnesium stearate to the ethylcellulose coating lowered the mechanical strength of the film and improved the robustness of the system.

Investigating the coating-dependent release mechanism of a pulsatile capsule using NMR microscopy

Chronopharmaceutical capsules, ethylcellulose-coated to prevent water ingress, exhibited clearly different release characteristics when coated by organic or aqueous processes. Organic-coated capsules produced a delayed pulse release, whereas aqueous-coated capsules exhibited less delayed and more erratic release behaviour. Nuclear magnetic resonance microscopy was used to elucidate the internal mechanisms underlying this behaviour by studying the routes of internal water transport and the timescale and sequence of events leading to the pulse. Images showed that the seal between the shell and the tablet plug is a key route of water penetration in these dosage forms. There is evidence for a more efficient seal in the organic-coated capsule, and although some hydration of the contents was evident, erosion of the tablet plug is most probably the controlling factor in timed release. The premature failure of the aqueous-coated capsule appears to be a result of rapid influx of water between plug and capsule with hydration of the low substituted hydroxypropylcellulose expulsion agent. As a result of this, the tablet plug remains intact, but appears unable to be ejected. The resulting significant pressure build-up causes premature release by distortion and splitting of the capsule shell. These events may be aided by a weakening of the aqueous-coated gelatin shell by hydration from the inside, and at the mouth of the capsule where previous electron microscope studies have shown incomplete coating of the inside by the aqueous process.

Time-dependent mechanical properties of polymeric coatings used in rupturable pulsatile release dosage forms

The mechanical properties of polymer films used in pharmaceutical coatings of pulsatile drug delivery systems were evaluated in the dry and the wet state by a newly developed puncture test, which allowed the time-dependent measurement of the mechanical properties on the same film specimen. Force, puncture strength, energy at break, modulus, and strain were investigated as a function of water exposure time with respect to the type of polymer and the type and concentration of plasticizer and pore former (hydroxypropyl methylcellulose, HPMC). Eudragit RS films were very flexible, had a high strain, and broke upon puncture with only small cracks. In contrast, ethylcellulose films were more brittle with a lower strain and showed complete film rupture. Increased amounts of the hydrophilic pore former, HPMC, resulted in a reduced puncture strength and in an increase in water uptake and weight loss of the films. The puncture strength decreased with increasing plasticizer concentration and was lower with the lipophilic dibutyl sebacate than with the hydrophilic triethyl citrate.

Manufacturing factors affecting the drug delivery function of thermo-responsive membrane prepared by adsorption of binary liquid crystals

A binary mixture of cholesteric oleyl carbonate (COC) and cholesteryl nonanoate (CN) with a weight ratio of 36% and 64% was adsorbed onto the cellulose nitrate membrane to prepare a thermo-responsive membrane. The thermo-responsive function of these COC/CN-adsorbed membranes was evaluated by an in vitro penetration study via repeatedly exchanging the temperature cycle. The manufacturing factors for preparing these thermo-responsive membranes, such as the binary COC/CN concentration used, immersion temperature of binary COC/CN chloroform solution, immersion temperature and time period of distilled water, vacuum-drying or air-drying process, and vacuum drying temperature, have been explored. The results indicated that the immersion temperature at 23 degrees C for membrane in binary COC/CN chloroform solution with 10 min and in distilled water with 12 h was the optimal temperature for fabricating the on-off thermo-responsive membranes prepared either by 22% or 25% concentration of binary COC/CN mixture. A good thermo-responsive function was further evidenced for these COC/CN-adsorbed membranes via vacuum-drying at 65 degrees C for 1 h. A possible mechanism concerning the thermal-dependent molecular motion, orientation and/or alignment of binary COC/CN mixture entrapped into the membrane may play an important role for the thermo-responsive behavior.

Modified release drug delivery in veterinary medicine

To successfully research and develop an animal pharmaceutical dosage form, a diverse array of issues covering basic medicine, pharmacology and technology must be addressed. Societal concerns regarding animal and public health, as well as the rapidly changing farming and economic environments, provide additional challenges that require integration into an already complex web of issues. Here, we examine the drive towards reducing the frequency of administration to animals and the closing of gaps between the human and veterinary drug product development.

Evaluation of Pulsincap to provide regional delivery of dofetilide to the human GI tract

Pulsincap formulations designed to deliver a dose of drug following a 5-h delay were prepared to evaluate the capability of the formulation to deliver dofetilide to the lower gastrointestinal (GI) tract. By the expected 5-h release time, the preparations were well dispersed throughout the GI tract, from stomach to colon. Plasma analysis permitted drug absorption to be determined as a function of GI tract site of release. Dofetilide is a well-absorbed drug, but showed a reduction in observed bioavailability when delivered from the Pulsincap formulations, particularly at more distal GI tract sites. Dispersion of the drug from the soluble excipient used in this prototype formulation relies on a passive diffusion mechanism and the relevance of this factor to the reduced extent and consistency of absorption from the colon is discussed. In these studies the effects of the degree of dispersion versus the site of dispersion could not be ascertained; nevertheless the scintigraphic analysis demonstrated good in vitro-in vivo correlation for time of release from Pulsincap preparations. The combination of scintigraphic and pharmacokinetic analysis permits identification of the site of drug release from the dosage form and pharmacokinetic parameters to be studied in man in a non-invasive manner.

In vitro and in vivo evaluation of an oral system for time and/or site-specific drug delivery

Aim of this work was the evaluation of an oral system (Chronotopic) designed to achieve time and/or site-specific release. The system consists in a drug-containing core, coated by a hydrophilic swellable polymer which is responsible for a lag phase in the onset of release. In addition, through the application of an outer gastroresistant film, the variability in gastric emptying time can be overcome and a colon-specific release can be sought relying on the relative reproducibility of small intestinal transit time. For this study, cores containing antipyrine as the model drug were prepared by tableting and both the retarding and enteric coatings were applied in fluid bed. The release tests were carried out in a USP 24 paddle apparatus. The in vivo testing, performed on healthy volunteers, envisaged the HPLC determination of antipyrine salivary concentration and a gamma-scintigraphic investigation. The in vitro release curves presented a lag phase preceding drug release and the in vivo pharmacokinetic data showed a lag time prior to the detection of model drug in saliva. Both in vitro and in vivo lag times correlate well with the applied amount of the hydrophilic retarding polymer. The gamma-scintigraphic study pointed out that the break-up of the units occurred in the colon. The obtained results showed the capability of the system in delaying drug release for a programmable period of time and the possibility of exploiting such delay to attain colon-targeted delivery according to a time-dependent approach.