LA PENETRATION PERCUTANEE DES MEDICAMENTS

SCOPUS: cp.jinfo:eu-repo/semantics/publishe

Gastroretentive dosage forms

This article begins with a review of gastric emptying, small intestine transit, and colonic transit of drug delivery systems with special attention paid to the different physiological processes involved in stomach emptying and to the cut-off size of nondigestible solids for passage through the gastroduodenal junction during the digestive phase. Then, the proposed means for prolonging the gastric residence time (GRT) of drug delivery systems are reviewed and analyzed with special emphasis on floating (F) dosage forms. The following means are discussed: the use of passage-delaying agents, large single-unit dosage forms, bioadhesive drug delivery systems, 'heavy' pellets, and buoyant forms. In the section devoted to bioadhesive forms, the influence of the turnover time of the intestinal mucus gel layer on the performance of mucoadhesive preparations is pointed out to explain the poor results obtained in humans with such peroral products. The use of a specifically designed apparatus for measuring the total force acting vertically on an object immersed in a liquid is presented as a methodology for selecting optimized buoyant formations in vitro. Scintigraphic studies are described in nonfasting human volunteers either in upright or in supine posture, who concurrently were given one optimized F and one nonfloating (NF) hydrophilic matrix capsules of the same size, for three different sizes (small, medium, and large). In upright subjects, the F forms stayed continuously above the gastric contents irrespective of their size, whereas the NF ones sank rapidly after administration and never rose back to the surface thereafter. Consequently, the F forms show prolonged and more reproducible GRTs compared to the NF ones. The significance and extent of this prolongation are the most marked for the small size units (p 0.05). Moreover, there is no significant difference between the mean GRTs of the small, medium, and large F units (p >0.05). This indirectly confirms that the intragastric buoyancy of the F forms is the main process determining their prolonged GRT and protecting them from random gastric emptying related to antral peristaltism. Thus, their GRT depends mainly on the occurrence of the end point of digestion. To the contrary, the lasting retention of the NF forms in the stomach is only size dependent. It appeared systematically with the large size units but not with all of the medium size units and never with the small size units (mean GRT small 0.05) because the F forms remain buoyant anywhere between the lesser and greater curvatures of the stomach. This position does not protect them from random emptying when they move distally toward the pylorus. Thus, in supine subjects, the GRTs of the F forms vary according to their size (mean GRT small 0.05) and they still increase with the size of the form (mean GRT small < medium < large units, p <0.05). Drawbacks related to the approach of GRT enhancement based on a size effect are discussed.SCOPUS: re.jinfo:eu-repo/semantics/publishe

BIODISPONIBILITE DES FORMES D'ADMINISTRATION RECTALE

SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe

RECHERCHE ET DEVELOPPEMENT DE FORMES ORALES A LIBERATION CONTROLEE

SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe

Suppositories formulation and drug release

SCOPUS: re.jinfo:eu-repo/semantics/publishe

Factors controlling the buoyancy and gastric retention capabilities of floating matrix capsules: New data for reconsidering the controversy

Optimized floating (F) and non-floating (NF) hydrophilic matrix capsules have been characterized in vitro with regard to their buoyancy or non- buoyancy capabilities and their diametral size evolution with time. The gastric residence times (GRTs) and transit behaviors of these F and NF forms prepared in small, medium, and large sizes were then comparatively examined in fed volunteers remaining either upright or supine. The results show that all the optimized F forms do lastingly float upon the gastric contents, whereas the NF forms sink rapidly after ingestion. In upright subjects, the F forms are consequently protected against postprandial emptying. The GRTs of the NF forms are much more variable and highly dependent on their size (mean GRT small < medium < large units, p < 0.05). The GRT prolongation obtained with the F forms when compared with the NF ones is hence significantly marked for the small and medium size dosage forms (p < 0.05) but not for the large ones (p ≥ 0.05). In supine subjects, a size effect influences the GRT of both the F and NF forms (p < 0.05). The F forms are more often emptied before the NF ones but, size for size, the mean GRTs do not differ in the aggregate. These findings, together with literature data, are used to explain why a number of former investigations have come to contradictory conclusions about the effect of density of an undigestible form on GRT. Uncontrolled factors are hiding from disclosure the GRT enhancement that should be observed when optimized F forms are used within defined conditions.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Influence of additives on the release profile of Nifedipine from poly-(DL-Lactide-co-glycolide) microspheres

info:eu-repo/semantics/publishe

Measuring the resultant-weight of an immersed test material: II. Examples of kinetic determinations applied to monolithic dosage forms

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

In vitro evaluation of the hydrolytic degradation of dispersed and aggregated poly(dl-lactide-co-glycolide) microspheres

info:eu-repo/semantics/publishe

Determination of thermal properties of acrylic polymer aqueous dispersions used for film coating

info:eu-repo/semantics/publishe