Evaluation of an enzyme-containing capsular shaped pulsatile drug delivery system

Cellulase as an "active" excipient in prolonged-release HPMC matrices: A novel strategy towards zero-order release kinetics

Hydrophilic matrices are of utmost interest for oral prolonged release of drugs. However, they show decreasing release rate over time, mainly due to lengthening of the diffusional pathway across the gel formed upon glass-rubber transition of the polymer. Therefore, achievement of zero-order release kinetics, which could reflect in constant drug plasma levels, is still an open issue. With the aim of improving the release performance of hydroxypropyl methylcellulose (HPMC) systems, the use of cellulolytic enzymes was proposed to aid erosion of the swollen matrix, thereby counteracting the release rate decrease particularly toward the end of the process. The effectiveness of this strategy was evaluated by studying the mass loss and drug tracer release from tableted matrices consisting of high-viscosity HPMC (Methocel® K4M), Acetaminophen and increasing amounts (0.5-10% on HPMC) of a cellulolytic product (Sternzym® C13030). A faster erosion and progressive shift to linearity of the overall release profiles were observed as a function of the enzyme concentration. Release was markedly linear from matrices containing 5 and 10% Sternzym® C13030. In partially coated matrices with these cellulase concentrations, such results were in agreement with data of erosion and swelling front movement, which exhibited early and long-lasting synchronization.

Controlling drug release with additive manufacturing-based solutions

3D printing is an innovative manufacturing technology with great potential to revolutionise solid dosage forms. Novel features of 3D printing technology confer advantage over conventional solid dosage form manufacturing technologies, including rapid prototyping and an unparalleled capability to fabricate complex geometries with spatially separated conformations. Such a novel technology could transform the pharmaceutical industry, enabling the production of highly personalised dosage forms with well-defined release profiles. In this work, we review the current state of the art of using additive manufacturing for predicting and understanding drug release from 3D printed novel structures. Furthermore, we describe a wide spectrum of 3D printing technologies, materials, procedure, and processing parameters used to fabricate fundamentally different matrices with different drug releases. The different methods to manipulate drug release patterns including the surface area-to-mass ratio, infill pattern, geometry, and composition, are critically evaluated. Moreover, the drug release mechanisms and models that could aid exploiting the release profile are also covered. Finally, this review also covers the design opportunities alongside the technical and regulatory challenges that these rapidly evolving technologies present.

Preparation of a colon-specific sustained-release capsule with curcumin-loaded SMEDDS alginate beads

A colon-specific capsule with alginate beads containing a self-microemulsifying drug delivery system (SMEDDS) was developed and evaluated.

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.

Modulation of a pulsatile release drug delivery system using different swellable/rupturable materials

Diclofenac sodium tablets consisting of core coated with two layers of swelling and rupturable coatings were prepared and evaluated as a pulsatile drug delivery system. Cores containing the drug were prepared by direct compression using microcrystalline cellulose and Ludipress as hydrophilic excipients with the ratio of 1:1. Cores were then coated sequentially with an inner swelling layer of different swellable materials; either Explotab, Croscarmellose sodium, or Starch RX 1500, and an outer rupturable layer of different levels of ethylcellulose. The effect of the nature of the swelling layer and the level of the rupturable coating on the lag time and the water uptake were investigated. Drug release rate studies were performed using USP paddle method. Results showed the dependence of the lag time and water uptake prior to tablet rupture on the nature of the swelling layer and the coating levels. Explotab showed a significant decrease in the lag time, followed by Croscarmellose sodium and finally by Starch RX 1500. Increasing the level of ethylcellulose coating retarded the diffusion of the release medium to the swelling layer and the rupture of the coat, thus prolonging the lag time.

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.

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.

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.

A pulsatile drug delivery system based on rupturable coated hard gelatin capsules

The objective of this study was to develop and evaluate a pulsatile drug delivery system based on drug-containing hard gelatin capsules, which were coated with a swelling layer and an outer insoluble, water-permeable polymeric coating. An inner pressure developed by the swelling layer resulted in the rupture of the outer coating. Preliminary studies with a simulated rupture test demonstrated the dependence of the lag time prior to rupture on the properties of the coating, such as its water permeability and mechanical strength. The lag time increased with a higher coating level, but decreased with the addition of the hydrophilic pore former, hydroxypropyl methylcellulose. Increasing the amount of the swelling layer decreased the lag time. The coated capsules took up release medium at a nearly constant rate until a critical maximum was reached, where the swelling pressure was sufficient to rupture the outer coating. The rate of medium uptake decreased with increasing coating level, while the extent of medium uptake was almost the same for the different coating levels. A hydrophobic particulate material, magnesium stearate, was added to the coating layer to reduce the mechanical strength and therefore the lag time. The test conditions, such as surfactant addition to the release medium or floating vs. complete immersion of capsules in the medium, affected the lag time.

Formulation parameters affecting the performance of coated gelatin capsules with pulsatile release profiles

The objective of this study was to develop and evaluate a rupturable pulsatile drug delivery system based on soft gelatin capsules with or without a swelling layer and an external water-insoluble but -permeable polymer coating, which released the drug after a lag time (rupturing of the external polymer coating). The swelling of the gelatin capsule itself was insufficient to rupture the external polymer coating, an additional swelling layer was applied between the capsule and the polymer coating. Croscarmellose sodium (Ac-Di-Sol) was more effective as a swelling agent than low and high molecular weight hydroxypropylmethyl cellulose (HPMC; E5 or K100M). Brittle polymers, such as ethyl cellulose (EC) and cellulose acetate propionate (CAPr), led to a better rupturing and therefore more complete drug release than the flexible polymer coating, Eudragit RS. The lag time of the release system increased with higher polymer coating levels and decreased with the addition of a hydrophilic pore-former, HPMC E5 and also with an increasing amount of the intermediate swelling layer. The water uptake of the capsules was linear until rupture and was higher with CAPr than with EC. Soft gelatin capsule-based systems showed shorter lag times compared to hard gelatin capsules because of the higher hardness/filling state of the soft gelatin capsules. The swelling pressure was therefore more directed to the external polymer coating with the soft gelatin capsules. Typical pulsatile drug release profiles were obtained at lower polymer coating levels, while the release was slower and incomplete at the higher coating levels. CAPr-coated capsules resulted in a more complete release than EC-coated capsules.

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.

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

We report the development of a chronopharmaceutical capsule drug delivery system capable of releasing drug after pre-determined time delays. The drug formulation is sealed inside the insoluble capsule body by an erodible tablet (ET). The release time is determined by ET erosion rate and increases as the content of an insoluble excipient (dibasic calcium phosphate) and of gel-forming excipient (hydroxypropylmethylcellulose; HPMC) increases. The time-delayed release of a model drug (propranolol HCI) was investigated by dissolution testing (USP XXIII paddle method). Both composition and weight of ET influence the time of drug release. Moreover it was found that drug release was controlled by the quantity of HPMC, irrespective of lactose content within the tablet weight range 80-160 mg, when above a threshold concentration of 20% HPMC. Programmable pulsatile release has been achieved from a capsule device over a 2-12-h period, consistent with the demands of chronotherapeutic drug delivery. The time of drug release can be controlled by manipulation of tablet formulation.