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Biomedical subjects

M T Sheu

Publications and source records attributed to M T Sheu.

25 records · Page 2Linked to original sources
PubMed1995

Papaverine and prostaglandin E1 gel applications for impotence.

The transdermal permeability of papaverine and prostaglandin E1 (PGE1) could be determined in vitro. A chemical scheme of passive delivery or with enhancer, as well as a physical iontophoretic transdermal delivery system were designed in the laboratory. Clinically, up to 20% papaverine base gel and 500 micrograms PGE1 were applied onto the genital area without any side effect. Only vascular response could be detected by ultrasound. However, immediate erection could not be obtained at the present dosage. Further research on the combination of skin absorption enhancers, the different chemical derivatives of PGE1 or a different administration route is warranted.

Administration, Cutaneous↗
PubMed1994

The influence of cosolvents on the in-vitro percutaneous penetration of diclofenac sodium from a gel system.

The influence of cosolovents on the in-vitro percutaneous penetration of diclofenac sodium from a gel system was studied using a simplex lattice experimental design. Gel formulations were prepared by gelling the vehicle mixture of water, alcohol and propylene glycol with Carbomer 940. The synthetic membrane Durapore and hairless mouse skin were employed as barriers in a Franz-type diffusion cell. It was found that the penetration through the synthetic membrane was well described by the Higuchi model. There existed a better inverse relationship between the penetration rate and the drug solubility in the respective vehicle. It appeared to be a membrane-controlled mechanism when using hairless mouse skin as the barrier. The penetration rates in steady-state for nine formulations were fitted to a polynomial equation based on this simplex lattice method. A three-dimensional plot was constructed in this simplex surface studied. The maximal penetration rate was found to be from the vehicle containing water and ethanol in an exact volume ratio of 3:1 and the minimal penetration rate was observed from the vehicle containing water only.

Acrylic Resins↗
PubMed1991

Prolongation of drug release by covalent bonding of drugs to serum albumin microbeads.

Reaction conditions for the covalent bonding of 5'-deoxy-5-fluorouridine to serum albumin microbeads by means of a water-soluble carbodiimide were studied. Optimum coupling of dFUR to the microbeads occurred when pure water was used as solvent. There was no significant difference in the bonding efficiency for microbeads prepared at different stirring speeds, and there was a limit to the amount of dFUR that could be bound with increasing reaction time. Yields were low possibly because of competing coupling reactions involving carbodiimide and other reactive groups in the protein. The release of dFUR from dFUR-bound microbeads was slow and biexponential. The fraction of dFUR bound in the interior of the microbeads increased with increasing reaction time.

Delayed-Action Preparations↗
PubMed1990

Drug release from glutaraldehyde-treated fibrin gels.

Glutaraldehyde treatment of dexamethasone-containing cylindrical fibrin gels (obtained by the thrombin-induced polymerization of fibrinogen in the presence of the drug) causes cross-linking of the gels and modification of the pore structure. The effect on the release of dexamethasone was assessed by measuring the diffusion coefficient of the drug across treated and untreated gels; diffusion across the treated gels was significantly decreased as compared with untreated gels, but was little affected by the concentration of glutaraldehyde used in the treatment. In biodegradable tests, the treated gels (all concentrations of glutaraldehyde) were resistant to digestion even in the presence of plasmin, but untreated gels were digested, and the digestion rate was accelerated by plasmin. The volume of the gels was progressively reduced as the concentration of glutaraldehyde was increased or the amount of fibrinogen was decreased, but the extent of the reduction did not correlate with the changes in the diffusion coefficient.

Biotransformation↗
PubMedDate not supplied

Fibrin based drug delivery systems.

Fibrinogen is the natural substrate for thrombin, the final proteolytic enzyme of the blood coagulation cascade. Following reaction with thrombin, fibrinogen is converted into fibrin monomers which then spontaneously polymerize into fibrin threads forming the fibrin matrix. This biochemical reaction between fibrinogen and thrombin has been used to produce natural, biodegradable, biocompatible systems for sustained drug delivery. Three potential delivery systems have been explored: 1) fibrin microparticles with drug entrapped are produced by an emulsion process, 2) reaction between fibrinogen adsorbed on suspended drug and thrombin in solution results in the formation of fibrin-coated drug particulates, and 3) fibrin sheets suitable as implants have been cast with drug entrapped. The drug release behavior of both small and large molecular weight substances from these systems was evaluated.

Delayed-Action Preparations↗