Development of a novel drug delivery system, time-controlled explosion system (TES): V. Animal pharmacodynamic study and human bioavailability study

Multiparticulate formulation approach to pulsatile drug delivery: current perspectives

In the body under physiological conditions, many vital functions are regulated by transient release of bioactive substances at a specific time and site. Thus, to mimic the function of living systems and in view of emerging chronotherapeutic approaches, pulsatile delivery, which is meant to release a drug following programmed lag phase, has attracted increasing interest in recent years. In pursuit of pulsatile release, various design strategies have been proposed, broadly categorized into single-unit and multiple-unit systems. However, in recent pharmaceutical applications involving pulsatile delivery, multiparticulate dosage forms are gaining much favor over single-unit dosage forms because of their potential benefits like predictable gastric emptying, no risk of dose dumping, flexible release patterns and increased bioavailability with less inter- and intra-subject variability. Based on these premises, the aim of the present review is to survey the main multiparticulate pulsatile delivery systems, for which the swelling and rupturing; dissolution or erosion; and changed permeability of the coating membrane are primarily involved in the control of release. The development of low density floating multiparticulate pulsed-release dosage forms possessing gastric retention capabilities has also been addressed with increasing focus on the upcoming multiparticulate-pulsatile technologies being exploited on an industrial scale.

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.

Process and Formulation Variables Affecting the Performance of a Rupturable Capsule‐Based Drug Delivery System with Pulsatile Drug Release

The objective of this study was to optimize several process and formulation parameters, which influence the performance of a rupturable, pulsatile drug delivery system. The system consisted of a drug-containing hard gelatin capsule, a swelling layer of croscarmellose (Ac-Di-Sol) and a binder, and an outer ethylcellulose coating. Polyvinyl pyrrolidone (Kollidon 90F) was superior to HPMC and HPC as a binder for the swelling layer with regard to binding (adherence to capsule) and disintegration properties of the swelling layer. The capsule-to-capsule uniformity in the amount of swelling layer and outer ethylcellulose coating, which significantly affected the lag time prior to rupture of the capsule, was optimized by decreasing the batch size, and by increasing the rotational pan speed and the distance between the spray nozzle and the product bed. The type of baffles used in the coating pan also affected the layering uniformity. Fully-filled hard gelatin capsules had a shorter lag time with a higher reproducibility compared to only half-filled capsules, because the swelling pressure was directed primarily to the outer ethylcellulose coating and not to the inner capsule core. Stability studies revealed that the lag time of the capsules was stable over a 240-day period when the moisture content was kept unchanged.

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.

An investigation of pulsatile release tablets with ethylcellulose and Eudragit L as film coating materials and cross-linked polyvinylpyrrolidone in the core tablets

To develop new pulsatile release tablets, which can suppress drug release in stomach and release the drug rapidly after a predetermined lag time of about 3 h in intestine, the use of tablets with ethylcellulose/Eudragit L as a coating film and cross-linked polyvinylpyrrolidone in the core tablets was investigated. The release of diltiazem hydrochloride (DIL) as a model drug in the core tablets was investigated in vitro. The lag time (t10) was prolonged with an increase of the coating level, whereas the drug release rate was almost constant, irrespective of the coating level. The water-uptake study and electron microscope photographs suggested the mechanism of pulsatile release of drug. Pulsatile release tablets containing 60 mg DIL with 4.4 h of lag time (t10) in vitro were administrated to eight volunteers. The mean plasma concentration curves showed 4.9 h of lag time (tlag), 8.0 h of time to maximum concentration (tmax) and 3.1 h of time between tmax and tlag (t(psi)) in vivo. Relative bioavailability was 1.05 for pulsatile release tablets compared to conventional tablets.