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Biomedical subjects

G E Amidon

Publications and source records attributed to G E Amidon.

7 recordsLinked to original sources
PubMed2001

Novel method to assess gastric emptying in humans: the Pellet Gastric Emptying Test.

To further validate the Pellet Gastric Emptying Test (PGET) as a marker of gastric emptying, a randomized, four-way crossover study was conducted with 12 healthy subjects. The study consisted of oral co-administration of enteric coated caffeine (CAFF) and acetaminophen (APAP) pellets in four treatment phases: Same Size (100 kcal), Fasted, Small Liquid Meal (100 kcal), and Standard Meal (847 kcal). The time of first appearance of measurable drug marker in plasma, t(initial), was taken as the emptying time for the markers. Co-administration of same size enteric coated pellets of CAFF and APAP (0.7 mm in diameter) revealed no statistically significant differences in t(initial) values indicating that emptying was dependent only on size and not on chemical make-up of the pellets. Co-administration of different size pellets indicated that the smaller 0.7-mm diameter (CAFF) pellets were emptied and absorbed significantly earlier than the larger 3.6-mm diameter (APAP) pellets with both the Small Liquid Meal (by 35 min) and the Standard Meal (by 33 min) (P<0.05). The differences in emptying of the pellets were not significant in the Fasted Phase. The results suggest that the pellet gastric emptying test could prove useful in monitoring changes in transit times in the fasted and fed states and their impact on drug absorption.

Acetaminophen↗
PubMed1998

Drug marker absorption in relation to pellet size, gastric motility and viscous meals in humans.

PURPOSE: The objective of this study was to evaluate drug marker absorption in relation to the gastric emptying (GE) of 0.7 mm and 3.6 mm enteric coated pellets as a function of viscosity and the underlying gastric motility. METHODS: Twelve subjects were evaluated in a 3-way crossover study. 0.7 mm caffeine and 3.6 mm acetaminophen enteric coated pellets were concurrently administered with a viscous caloric meal at the levels of 4000, 6000 and 8000 cP. Gastric motility was simultaneously measured with antral manometry and compared to time events in the plasma profiles of the drug markers. RESULTS: Caffeine, from the 0.7 mm pellets, was observed significantly earlier in the plasma than acetaminophen, from the 3.6 mm pellets, at all levels of viscosity. Motility related size differentiated GE was consistently observed at all viscosity levels, however, less variability was observed with the 4000 cP meal. Specifically, the onset of absorption from the of 3.6 mm pellets correlated with the onset of Phase II fasted state contractions (r = 0.929, p < 0.01). CONCLUSIONS: The timeframe of drug marker absorption and the onset of motility events were not altered within the range of viscosities evaluated. Rather, the differences in drug marker profiles from the non-digestible solids were most likely the result of the interaction between viscosity and motility influencing antral flow dynamics. The administration of the two sizes of pellets and a viscous caloric meal with subsequent monitoring of drug marker profiles is useful as a reference to assess the influence of motility patterns on the absorption profile of orally administered agents.

Acetaminophen↗
PubMed1995

The effect of moisture on the mechanical and powder flow properties of microcrystalline cellulose.

PURPOSE: This study determined the effects of moisture on the mechanical and powder flow properties of microcrystalline cellulose. METHODS: A variety of mechanical properties were determined as a function of solid fraction at moisture levels ranging from 0 to 12.2% and included: compaction pressure required to form a compact, dynamic indentation hardness, quasi-static indentation hardness, tensile strength, best case and worst case Bonding Index, Brittle Fracture Index, Strain Index, Compressibility Index and shear cell index. RESULTS: Significant changes were observed as the moisture level of microcrystalline cellulose increased. The compaction pressure required to produce a compact at a solid fraction of 0.6 decreased with increasing moisture content. The permanent deformation pressure and tensile strength of compacts were observed to be relatively independent of moisture content below about 5% moisture and then decrease as the moisture content increased further. The "best case" Bonding Index was also observed to be independent of moisture content below 5% and then increase with increasing moisture. The Brittle Fracture Index and "worst case" Bonding Index, however, did not appear to be affected by changes in moisture content. Powder flow was shown to decrease with increasing moisture content. CONCLUSIONS: These mechanical property data are consistent with the hypothesis that water acts as a plasticizer and influences the mechanical properties of microcrystalline cellulose. At moisture levels above about 5%, the material exhibits significant changes consistent with a transition from the glassy state to the rubbery state.

Cellulose↗
PubMed1992

Microscopic characterization of particle size and shape: an inexpensive and versatile method.

A variety of methods exists for measuring individual particle dimensions as a means of characterizing particle size, size distribution, and shape. The equipment described in this report belongs to the class of semiautomatic non-TV-interfaced analyzers. Unlike many existing image analysis systems, three-dimensional form measurements and texture data for the calculation of particle size and shape parameters can be determined easily and directly from each particle profile using this system. Essentially all data are collected directly from the particle and recorded by the computer with no intermediate steps. Much of the system consists of general-purpose and relatively inexpensive, commercially available hardware and software. Using this method, particle size, size distribution, and qualitative or quantitative shape information can easily and rapidly be obtained simultaneously. Particle length and width characterization, for example, can take less than 15 min. The equipment is versatile and flexible in measurements and calculations. The size and shape parameters to be measured are determined by the researcher and not the instrument. The ease with which this information can be obtained from small samples early in the development process makes it a valuable tool for the formulator.

Chemistry, Pharmaceutical↗
PubMed1982

Theoretical and experimental studies of transport of micelle-solubilized solutes.

A physical model describing the simultaneous diffusion of free solute and micelle-solubilized solute across the aqueous boundary layer, coupled with partitioning and diffusion of free solute through a lipoidal membrane, is derived. In vitro experiments utilizing progesterone and polysorbate 80 showed excellent agreement between theoretical predictions based on independently determined parameters and experimental results. The physical model predicts that micelles can assist the transport of solubilized solute across the aqueous diffusion layer, resulting in a higher solute concentration at the membrane surface than would be predicted if micelle diffusion is neglected. At high surfactant concentrations, the aqueous diffusion layer resistance can be eliminated and the activity of the solute at the membrane can approach the bulk solute activity. This mechanism could explain observed enhanced absorption rates in vivo when both micelle solubilization occurs and the aqueous diffusion layer is an important transport barrier. The importance of determining and defining the thermodynamic activity of the diffusing solute is emphasized.

Biological Transport↗
PubMed1981

Rotary press utilizing a flexible die wall.

A die with a flexible wall was constructed and evaluated on a specially modified instrumented rotary tablet press. The design permits an inward deflection of the die wall by a side punch, which rolls past a side compression roll during compression-decompression. The side compression roll is instrumented to monitor the applied side compression roll forces. On decompression, return of the die wall to its original position permits release of residual die wall pressure. The decreased residual die wall pressure can decrease fracture and capping of tablets for problem formulations. The performance was tested on three experimental formulations. For these formulations, tablets made in a conventional die exhibited severe capping problems. However, most tablets compressed in the special die were superior. With proper adjustment of punch and die wall compression forces, excellent tablets could be manufactured. The merits of the special die and modified tablet machine are substantiated, although this initial design did not provide adequate die wall pressure for all formulations. Further engineering efforts could result in practical production equipment.

Acetaminophen↗