In-vivo monitoring of dosage forms

A review of emerging technologies enabling improved solid oral dosage form manufacturing and processing

Tablets are the most widely utilized solid oral dosage forms because of the advantages of self-administration, stability, ease of handling, transportation, and good patient compliance. Over time, extensive advances have been made in tableting technology. This review aims to provide an insight about the advances in tablet excipients, manufacturing, analytical techniques and deployment of Quality by Design (QbD). Various excipients offering novel functionalities such as solubility enhancement, super-disintegration, taste masking and drug release modifications have been developed. Furthermore, co-processed multifunctional ready-to-use excipients, particularly for tablet dosage forms, have benefitted manufacturing with shorter processing times. Advances in granulation methods, including moist, thermal adhesion, steam, melt, freeze, foam, reverse wet and pneumatic dry granulation, have been proposed to improve product and process performance. Furthermore, methods for particle engineering including hot melt extrusion, extrusion-spheronization, injection molding, spray drying / congealing, co-precipitation and nanotechnology-based approaches have been employed to produce robust tablet formulations. A wide range of tableting technologies including rapidly disintegrating, matrix, tablet-in-tablet, tablet-in-capsule, multilayer tablets and multiparticulate systems have been developed to achieve customized formulation performance. In addition to conventional invasive characterization methods, novel techniques based on laser, tomography, fluorescence, spectroscopy and acoustic approaches have been developed to assess the physical-mechanical attributes of tablet formulations in a non- or minimally invasive manner. Conventional UV-Visible spectroscopy method has been improved (e.g. fiber-optic probes and UV imaging-based approaches) to efficiently record the dissolution profile of tablet formulations. Numerous modifications in tableting presses have also been made to aid machine product changeover, cleaning, and enhance efficiency and productivity. Various process analytical technologies have been employed to track the formulation properties and critical process parameters. These advances will contribute to a strategy for robust tablet dosage forms with excellent performance attributes.

19F MR imaging golden angle-based capsule tracking for intestinal transit and catheter tracking: initial in vivo experience

PURPOSE

To combine fluorine 19 ((19)F) magnetic resonance (MR) imaging and golden angle radial acquisition and to assess the feasibility of (19)F MR imaging golden angle-based tracking for catheter tracking applications and simultaneous three-dimensional (3D) intestinal tracking of ingested (19)F-labeled capsules in vivo.

MATERIALS AND METHODS

Approval from the local ethical committee and informed consent from the subject were obtained. In vitro studies were performed to assess (19)F MR imaging golden angle-based tracking reliability with regard to temporal resolution and different tracking strategies (boundary condition-free tracking, composite image-based tracking, and model-based tracking). In vivo performance of the method was investigated in one healthy volunteer on 2 days. On study day 1, a duodenal catheter incorporating five (19)F-labeled capsules was administered nasally, and its 3D movement was tracked inside the stomach and esophagus. On study day 2, three (19)F-labeled capsules were swallowed, and intestinal movement was tracked.

RESULTS

Simultaneous in vivo 3D tracking of multiple (19)F-labeled capsules was successfully performed without incorporation of boundary conditions at a temporal resolution of 252 msec. Incorporation of boundary conditions with composite image-based tracking and model-based tracking increased tracking reliability and enabled temporal resolution as high as 108 msec.

CONCLUSION

Use of (19)F MR imaging golden angle-based capsule tracking enables in vivo tracking of (19)F-labeled capsules and catheters at high temporal resolution. The presented method is applicable to physioanatomic studies of the gastrointestinal tract and shows potential for real-time tracking in interventional radiology.

Ocular pharmacokinetic study using T₁ mapping and Gd-chelate- labeled polymers

PURPOSE

Recent advances in drug discovery have led to the development of a number of therapeutic macromolecules for treatment of posterior eye diseases. We aimed to investigate the clearance of macromolecular contrast probes (polymers conjugated with Gd-chelate) in the vitreous after intravitreal injections with the recently developed ms-DSEPI-T12 MRI and to examine the degradation of disulfide-containing biodegradable polymers in the vitreous humor in vivo.

METHODS

Intravitreal injections of model contrast agents poly[N-(2-hydroxypropyl)methacrylamide]-GG-1,6-hexanediamine-(Gd-DO3A), biodegradable (Gd-DTPA)-cystine copolymers, and MultiHance were performed in rabbits; their distribution and elimination from the vitreous after injections were determined by MRI.

RESULTS

Times for macromolecular contrast agents to decrease to half their initial concentrations in the vitreous ranged from 0.4-1.3 days post-injection. Non-biodegradable polymers demonstrated slower vitreal clearance than those of disulfide-biodegradable polymers. Biodegradable polymers had similar clearance as MultiHance.

CONCLUSIONS

Usefulness of T(1) mapping and ms-DSEPI-T12 MRI to study ocular pharmacokinetics was demonstrated. Results suggest an enzymatic degradation mechanism for the disulfide linkage in polymers in the vitreous leading to breakup of polymers in vitreous humor over time.

MRI in ocular drug delivery

Conventional pharmacokinetic methods for studying ocular drug delivery are invasive and cannot be conveniently applied to humans. The advancement of MRI technology has provided new opportunities in ocular drug-delivery research. MRI provides a means to non-invasively and continuously monitor ocular drug-delivery systems with a contrast agent or compound labeled with a contrast agent. It is a useful technique in pharmacokinetic studies, evaluation of drug-delivery methods, and drug-delivery device testing. Although the current status of the technology presents some major challenges to pharmaceutical research using MRI, it has a lot of potential. In the past decade, MRI has been used to examine ocular drug delivery via the subconjunctival route, intravitreal injection, intrascleral injection to the suprachoroidal space, episcleral and intravitreal implants, periocular injections, and ocular iontophoresis. In this review, the advantages and limitations of MRI in the study of ocular drug delivery are discussed. Different MR contrast agents and MRI techniques for ocular drug-delivery research are compared. Ocular drug-delivery studies using MRI are reviewed.

Gastrointestinal transit and disintegration of enteric coated magnetic tablets assessed by ac biosusceptometry

The oral administration is a common route in the drug therapy and the solid pharmaceutical forms are widely used. Although much about the performance of these formulations can be learned from in vitro studies using conventional methods, evaluation in vivo is essential in product development. The knowledge of the gastrointestinal transit and how the physiological variables can interfere with the disintegration and drug absorption is a prerequisite for development of dosage forms. The aim of this work was to employing the ac biosusceptometry (ACB) to monitoring magnetic tablets in the human gastrointestinal tract and to obtain the magnetic images of the disintegration process in the colonic region. The ac biosusceptometry showed accuracy in the quantification of the gastric residence time, the intestinal transit time and the disintegration time (DT) of the magnetic formulations in the human gastrointestinal tract. Moreover, ac biosusceptometry is a non-invasive technique, radiation-free and harmless to the volunteers, as well as an important research tool in the pharmaceutical, pharmacological and physiological investigations.

Analysis of the meal-dependent intragastric performance of a gastric-retentive tablet assessed by magnetic resonance imaging

BACKGROUND

Modern medical imaging modalities can trace labelled oral drug dosage forms in the gastrointestinal tract, and thus represent important tools for the evaluation of their in vivo performance. The application of gastric-retentive drug delivery systems to improve bioavailability and to avoid unwanted plasma peak concentrations of orally administered drugs is of special interest in clinical and pharmaceutical research.

AIM

To determine the influence of meal composition and timing of tablet administration on the intragastric performance of a gastric-retentive floating tablet using magnetic resonance imaging in the sitting position.

METHODS

A tablet formulation was labelled with iron oxide particles as negative magnetic resonance contrast marker to allow the monitoring of the tablet position in the food-filled human stomach. Labelled tablet was administered, together with three different solid meals, to volunteers seated in a 0.5-T open-configuration magnetic resonance system. Volunteers were followed over a 4-h period.

RESULTS

Labelled tablet was detectable in all subjects throughout the entire study. The tablet showed persistent good intragastric floating performance independent of meal composition. Unfavourable timing of tablet administration had a minor effect on the intragastric tablet residence time and floating performance.

CONCLUSION

Magnetic resonance imaging can reliably monitor and analyse the in vivo performance of labelled gastric-retentive tablets in the human stomach.

A novel pH- and time-dependent system for colonic drug delivery

A novel pH- and time-dependent delivery system was developed for delivering drugs to the colon. In vitro studies showed that this novel system could release the drug at a predetermined time, which was mainly controlled by the coating layers of the system. The delayed time of the press-coating layer was controlled by its erosion rate, which followed Hixson-Crowell equation. A proper selection of such factors as the viscosity grade of HPMC and tablet hardness, etc., can help reproduce the drug release profile as expected. The transit profiles in two healthy volunteers by gamma scintigraphy demonstrated that the tablets were able to pass through the stomach and small intestine intact and could safely reach the distal end of the small intestine, where the system began to release the drug contained in the core tablet. For both of the volunteers, disintegration of the tablets occurred in the ascending colon, which had highlighted the potential of this system for colonic drug delivery.

Study on of bioadhesive property of carbomer934 by a gamma camera in vivo

AIM: To study the bioadhesive property of carbomer934 in dog alimentary tract.

METHODS: Carbomer934 and ethylcellulose were radiolabelled with technetium-99 m; and Gastrointestinal emptying rate of materials was measured using the technique of gamma scintigraphy.

RESULTS: After oral administration, the maximum intestinal radioactivity of non-bioadhesive granules and bioadhesive granules were observed in the second hour and the sixth hour respectively. Constants of stomach emptying rate of nonadhesive granules, bioadhesive granulesI and bioadhesive granulesII were 0.774 h^-1,0.265 h^-1 and 0.321 h^-1 respectively on the base of gastric residual amount. Compared to nonadhesive material (ethylcellulose), the migration rate of adhesive material(carbomer934) was remarkably slower in dog alimentary canal.

CONCLUSION: It is concluded that, in the dog, interactions between gastrointestinal mucus layer and adhesive material or nonadhesive material were significantly different. Carbomer934 had stronger in vivo bioadhesive property than ethylcellulose.

Effects of meal consistency and ingested fluid volume on the intragastric distribution of a drug model in humans--a magnetic resonance imaging study

BACKGROUND

Controlled delivery of drugs to the small intestine in relation to emptying of an ingested meal is important in various pathophysiological conditions. We investigated the effects of different food consistencies and the amount of co-ingested liquid on the intragastric distribution of a contrast marker.

METHODS

Five healthy subjects received four meals (each 650 kcal: A, mashed potato with 100 mL water; B, rice with 100 mL water; C, hamburger meal with 100 mL water; D, hamburger meal with 300 mL water). A capsule filled with gadolinium tetra-azacyclododecane tetra-acetic acid solution (as contrast marker) was ingested following meal termination, and its intragastric distribution was assessed by magnetic resonance imaging.

RESULTS

Initially, marker distribution was confined to the fundus, and subsequently extended along the inner curvature of the stomach. The maximum distribution volume of the marker was lower in meal A than in meal B (P < 0.05). No differences in marker distribution were observed when the hamburger meal was given with 100 or 300 mL water.

CONCLUSIONS

The intragastric distribution kinetics of the marker gadolinium tetra-azacyclododecane tetra-acetic acid appeared to depend on meal consistency, but not on the amount of water co-ingested. Three-dimensional magnetic resonance imaging allows detailed analysis of the intragastric distribution of a drug model in relation to meal emptying and intragastric meal distribution.

Magnetic marker monitoring of disintegrating capsules

Magnetic marker monitoring was studied for its applicability to investigate the in vivo fate and behavior of disintegrating magnetically marked dosage forms. As a model, hard gelatin capsules were filled with an effervescent mixture of lactose, ascorbic acid and sodium hydrogen carbonate containing 1.3 mg black iron oxide as a magnetic label. The accuracy of the localization procedure whilst calculating all parameters of the dipole in one fitting procedure was checked in phantom experiments where the capsules were moved in well-defined paths with respect to the measurement device. The calculated position coordinates of the capsules deviated between less than 2 mm up to 8 mm from the expected position values depending on the distance between the sensor area and the capsule's path. Further experiments on the in vitro disintegration of the capsules showed that the value of the magnetic moment of the capsules can serve as a measure for their disintegration behavior. In vivo monitoring of the capsules was performed in eight experiments where a healthy volunteer swallowed each time one of the capsules. It was found that the in vivo disintegration behavior of the capsules corresponds well to their disintegration observed in water of about 37 degrees C.