http://depa.fquim.unam.mx/amyd/archivero/Modeling-CrusRamirezyVargasPavonyJimenezSolorzano_11276.pdf

Modeling and comparison of dissolution profiles.

Overview of membrane science and technology membrane transport theory membrane and modules concentration polarization reverse osmosis ultrafiltration microfiltration gas separation pervaporation ion exchange membrane processes - electrodialysis carrier facilitated transport medical applications of membranes other membranes processed.

Membrane Technology and Applications

A simple equation for description of solute release I. Fickian and non-fickian release from non-swellable devices in the form of slabs, spheres, cylinders or discs

Modeling of drug release from delivery systems based on hydroxypropyl methylcellulose (HPMC).

Recent advances on chitosan-based micro- and nanoparticles in drug delivery.

There is provided novel and useful pro-drug forms of theophylline having the formula: ##STR1## wherein R represents a member selected from the group consisting of a straight or branched C4 -C20 alkyl group, a straight or branched C14 -C20 alkenyl group, a substituted phenyl group or a substituted or unsubstituted naphthyl group whose substituents are selected from the group consisting of a hydroxy group, a C1 -C4 alkyl group, a C1 -C4 alkoxy group, a C1 -C14 acyloxy group, and a halogen atom (Cl, Br, I), and a substituted or unsubstituted heteroaromatic group whose substituents are selected from the group consisting of a hydroxy group, a C1 -C4 alkyl group, a C1 -C4 alkoxy group, a C1 -C4 acyloxy group, and a halogen atom (Cl, Br, I), and wherein A presents a member selected from the group consistng of a --CO-- group, a --CO--(CH2)n --C-- group, wherein n represents an integer of from 1 to 16, a --CO--CH=CH--CO-- group (cis or trans), ##STR2## AND A ##STR3## group. The compounds of this invention are useful in the treatment of asthma in warm-blooded animals. Upon administration, the compounds of this invention slowly go into solution and subsequently cleave prior to and/or during the absorption process, releasing theophylline in a sustained manner at a non-toxic, therapeutic level; that is, without the large blood level variations normally observed when theophylline per se is administered.

Useful pro-drug forms of theophylline

It has been shown that the interactions between sarcosine anhydride, a cyclic dieptide, and forty-six organic proton donor compounds result in the formation of both soluble and insoluble molecular complexes. The studies illustrate the importance of the aromatic and hydrophobic character of the molecule, as well as the nature of the polar groups and their positions, on complexin activity. The stoichiometry of a large number of insoluble complex species found were determined from analysis of phase diagrams and chemical analysis of the solid materials. Apparent stability constants were determined for the soluble complexes formed in the investigation. It is suggested that many biochemical and drug actions are mediated through formation of complexes of this type.

Complexes formed in aqueous solutions by sarcosine anhydride; interactions with organic acids, phenols, and aromatic alcohols.

Investigation of the complexing reaction between polyethylene glycol and iodine in an iodine-potassium iodide aqueous system has shown that at high triodide ion concentrations and low free iodine concentrations an insoluble complex having a stoichiometric ratio of one mole of potassium triodide to approximately 10 monomeric units of the polymer is reversibly formed. Potassium ion is apparently a prerequisite for formation of this complex. At much higher free iodine concentrations a second insoluble complex containing a considerable amount of iodine per se is reversibly formed from the first. The stoichiometry of the second complex formed appears to be such that one molecule of iodine is taken up by two monomeric units of ethylene oxide in the polymeric chain. The concentration dependencies of both complexing reactions on iodide, potassium ion and free iodine are presented in this report. The interaction in a sodium iodide-iodine system also results in the formation of an insoluble complex. This interaction does not appear to be analagous to that in the potassium iodide-iodine system. Bromine in the presence of bromide ion has also been shown to form a reversible insoluble complex with polyethylene

Study of Possible Complex Formation BetweenMacromolecules and Certain Pharmaceuticals IX: Formation of Iodine-Iodide Complexes with Polyethylene Glycol: Formation of Iodine-Iodi de Complexes with Polyethylene Glycol

The adsorption of sarin from n -heptane solutions by silica gels, alumina, bentonite, and certain carbonaceous adsorbents was studied. The results obtained have been interpreted according to the Langmuir adsorption isotherm. Of the various adsorbents tested, those of a silicaceous nature were found to be superior, exhibiting very strong adsorptive tendencies toward the fluorophosphate ester. A linear relationship was found to exist between the limiting adsorptive capacity and the specific surface area of the adsorbents. The average area occupied by a sarin molecule, furthermore, was found to be approximately 80 A 2 , irrespective of the adsorbent, a value in reasonable agreement with that suggested by a molecular model. Both of these relationships indicate that sarin is adsorbed primarily as a unimolecular layer.

Takeru Higuchi

Papers

Useful pro-drug forms of theophylline

Complexes formed in aqueous solutions by sarcosine anhydride; interactions with organic acids, phenols, and aromatic alcohols.

Study of Possible Complex Formation BetweenMacromolecules and Certain Pharmaceuticals IX: Formation of Iodine-Iodide Complexes with Polyethylene Glycol: Formation of Iodine-Iodi de Complexes with Polyethylene Glycol

Investigation and Development of Protective Ointments III*: Adsorption characteristics of sarin from solutions

Scientific EditionInhibition of Hydrolysis of Esters in Solution Formation of Complexes III.*: Stabilization of Tetracaine with Caffeine