The influence of tablet density on the human oral absorption of sustained release acetaminophen matrix tablets

Decades of research in drug targeting to the upper gastrointestinal tract using gastroretention technologies: where do we stand?

A major constraint in oral controlled release drug delivery is that not all the drug candidates are absorbed uniformly throughout the gastrointestinal tract (GIT). Drugs having "absorption window" are absorbed in a particular portion of GIT only or are absorbed to a different extent in various segments of the GIT. Thus, only the drug released in the region preceding and in close vicinity to the absorption window is available for absorption. The drug must be released from the dosage form in solution form; otherwise, it is generally not absorbed. Hence, much research has been dedicated to the development of gastroretentive drug delivery systems that may optimize the bioavailability and subsequent therapeutic efficacy of such drugs, as these systems have unique properties to bypass the gastric emptying process. These systems show excellent in vitro results but fail to give desirable in vivo performance. During the last 2-3 decades, researchers from the academia and industries are giving considerable importance in this field. Unfortunately, till date, few so-called gastroretentive dosage forms have been brought to the market in spite of numerous academic publications. The manuscript considers strategies that are commonly used in the development of gastroretentive drug delivery systems with a special attention on various parameters, which needs to be monitored during formulation development.

An effect of cellulose crystallinity on the moisture absorbability of a pharmaceutical tablet studied by near-infrared spectroscopy

In this study, we investigated molecular-level variation of tablets caused by grinding and its effect on their actual moisture absorbability. Model tablets contained acetaminophen as an active pharmaceutical ingredient and microcrystalline cellulose (MCC) as an excipient. Different levels of grinding were applied during the tablet formulation to intentionally cause the structural variation of the MCC. The moisture absorbability of tablets showed obvious variation depending on the grinding time, and the corresponding change in near-infrared spectra was readily captured. The detailed analysis of the variation of the band frequencies (i.e., wavenumber) revealed that the grinding process substantially disintegrates the crystalline and generates a glassy amorphous structure of MCC, which is a requirement to absorb water molecules. Consequently, it is very likely that the change of the moisture absorbability of the tablets is closely related to the development of the amorphous structure. These results indicate that the pharmaceutical product performances can be influenced by the physical properties of the excipient, which in turn can be controlled by the grinding process.

Development of a gastric retentive system as a sustained-release formulation of pranlukast hydrate and its subsequent in vivo verification in human studies

Pranlukast hydrate was demonstrated in a human site-of-absorption study to have extremely poor absorption properties in the lower gastrointestinal tract. The ratios of AUC0-24 in the distal small bowel and colon compared to stomach delivery were approximately 1/7 and 1/70, respectively. As a consequence, a gastroretentive double-layered tablet formulation (gastric swelling system; GSS), consisting of a swelling layer and a drug release layer, was developed for once-daily dosing. To study the gastric retention of the optimized GSS, an in vivo gamma scintigraphic study was carried out in nine healthy volunteers. The transit profiles demonstrated that the GSS was retained in the stomach for more than 10h. The plasma profile was prolonged, especially following administration after an evening meal. The human data validated the design concept and suggest that GSS could be a promising approach for the development of sustained-release formulation for drugs with a limited absorption window in the upper small bowel.

Evaluation of different screening methods to understand the dissolution behaviors of amorphous solid dispersions

OBJECTIVE

The objectives of the current study were to understand the dissolution behaviors of amorphous solid dispersions (ASD) using different screening methods and their correlation to the dissolution of formulated products.

MATERIALS AND METHODS

A poorly soluble compound, compound E, was used as a model compound. ASDs were prepared with HPMC, Kollidon VA64 and Eudragit EPO using hot-melt extrusion. Different techniques including precipitation, powder, capsule and compact dissolution and the dissolution of formulated products were conducted in USP simulated gastric fluid using a USP II dissolution apparatus.

RESULTS AND DISCUSSIONS

It was found that a precipitation study could generally predict powder, capsule and compact dissolution. Yet, it was recommended to run the dissolution at a higher paddle speed or for a longer duration to improve the predictability. It was also recommended to run powder, capsule and compact dissolution at both slow and high speeds to gain insights into wetting, dispersion and the dissolution of a system. Sometimes, capsule or compact dissolution could not be predicted by precipitation or powder dissolution due to plug formation. In this case, properly designed dosage forms were needed to break up this plug to optimize the dissolution profiles. On the contrary, formulations and dissolution conditions would have minimal effects on the dissolution profiles of a fast-dissolving solid dispersion.

CONCLUSIONS

Different techniques are available to select the right polymers to optimize dissolution behaviors. However, it is important to understand the merits and limitations of each technique in order to optimize the formulations for amorphous solid dispersions.

A Critical Review of Gastric Retentive Controlled Drug Delivery

The promise of gastric retentive drug delivery systems has propagated numerous investigations and the formation of a number of companies. Three technologies have involved a substantial number of human clinical trials: mucoadhesion, density modification, and expansion. Standard, nondisintegrating controlled-release tablets can display significant gastric retention times, with that retention time being proportional to the calorie intake. When these data for standard tablets are factored in, gastric retention technologies do not appear to offer significant additional retention times. Although the goal remains valuable, the promise of gastric retentive drug delivery systems remains unfulfilled at this time.

Floating drug delivery systems: a review

The purpose of writing this review on floating drug delivery systems (FDDS) was to compile the recent literature with special focus on the principal mechanism of floatation to achieve gastric retention. The recent developments of FDDS including the physiological and formulation variables affecting gastric retention, approaches to design single-unit and multiple-unit floating systems, and their classification and formulation aspects are covered in detail. This review also summarizes the in vitro techniques, in vivo studies to evaluate the performance and application of floating systems, and applications of these systems. These systems are useful to several problems encountered during the development of a pharmaceutical dosage form.

Investigation of prandial effects on hydrophilic matrix tablets

The prolonged release of drug from hydrophilic matrix tablets can be greatly affected by administration in connection with the intake of food. Changes of the tablet erosion are one of the main components of this effect. The aim of the present study was to identify the postprandial factors responsible for changes in tablet erosion and to develop predictive in vitro tests. Two formulations, one sensitive and the other robust to prandial effects in vivo, were investigated in vitro (a) in a complex physiological media simulating fasting and fed conditions; (b) according to a factorial experimental design that included agitation and pH concentrations of salt, surface-active agent, and nonionic solute as factors; and (c) at varying agitation intensities in three different sets of dissolution apparatus. Of the studied factors, only increased agitation enhanced the erosion of tablets in accordance with the in vivo effects of a meal. The other factors retarded erosion or had only minor effects. The hydrodynamic mechanical stress was thus considered to be the main factor responsible for postprandial effects on tablet erosion. The influence of changes in agitation and the opportunity to discriminate between sensitive and robust formulations differed among the three sets of dissolution apparatus. The modified USP II apparatus, operated at speeds of 50 and 100 rpm, is proposed as a discriminatory test.