Biomedical subjects

C D Melia

Publications and source records attributed to C D Melia.

26 records · Page 2Linked to original sources

PubMed1990

The application of Fourier-transform Raman spectroscopy to the analysis of pharmaceuticals and biomaterials.

Near infrared Fourier-transform (FT) Raman spectroscopy is shown to be a useful spectroscopic tool for the molecular structural analysis of drugs and biomedical polymers. The technique has been applied to the non-invasive investigation of the hydrolytic degradation of a biodegradable polymer in water over a period of 15 days and to the analysis of a drug within a polymer vehicle over a wide drug concentration range. This work demonstrates the potential value of FT Raman spectroscopy in the field of pharmaceutical science.

Anhydrides↗

PubMed1990

Transdermal delivery of theophylline to premature infants using a hydrogel disc system.

1. Preterm infants show incompletely developed skin with reduced barrier function. The possibility of transdermal delivery of theophylline from hydrogel discs swollen with choline theophyllinate has been investigated. 2. Drug loaded hydrogel discs 2 cm2 in area were applied to the abdomen and occluded. Serum theophylline concentrations were measured in twenty-one infants of less than 31 weeks gestation. 3. Therapeutic concentrations were achieved in 18 individuals, and maintained for up to 15 days after repeated application of discs. A correlation between maximum serum drug concentration and transepidermal water loss, gestation and birthweight was demonstrated.

Administration, Cutaneous↗

PubMed1990

Microencapsulation using emulsification/solvent evaporation: an overview of techniques and applications.

This review describes the microencapsulation of pharmaceuticals using the technique of emulsification-solvent evaporation. Guidelines are given for development of encapsulation processes for drugs with either high or low aqueous solubilities. Methods for microsphere characterization and assessment are detailed. The properties of a range of encapsulating polymers are described with examples of drugs encapsulated. The article concludes by speculating the clinical potential of microsphere-based drug delivery systems.

Animals↗

PubMed1989

Review article: mechanisms of drug release from tablets and capsules. I: Disintegration.

Variable drug release from solid oral dosage forms has been an important cause of bioavailability problems in the past, and is a factor now carefully controlled in pharmaceutical products. In two reviews, we describe briefly the composition and manufacture of tablets and capsules, and the two main processes by which they release drugs; disintegration and dissolution. We will explain what is presently understood of the actual mechanisms of drug release and the physico-chemical factors that affect the release process. The strategies adopted by pharmaceutical scientists in designing modern oral solid dose forms to release drugs at reproducible and therapeutically optimal rates will be discussed. Finally, the role of gamma scintigraphy in assessing dosage form performance in vivo will be described.

Biological Availability↗

PubMed1989

Review article: mechanisms of drug release from tablets and capsules. 2. Dissolution.

Optimal drug dissolution is crucial to the success of oral drug therapy. Slow dissolution has frequently been correlated with poor or erratic performance of oral dosage forms in vivo, and drugs of low aqueous solubility provide a major challenge to the designer of modern oral dosage forms. In this second of two reviews, we briefly describe the physical process of dissolution, the principal factors controlling drug dissolution from tablets and capsules, and the strategies that are utilized by pharmaceutical scientists to enhance drug dissolution of orally administered drugs.

Animals↗

PubMed1989

Gastrointestinal transit of Sinemet CR in healthy volunteers.

The gastrointestinal transit and systemic absorption of Sinemet CR (50/200) and standard Sinemet (25/100) have been studied in fasting and "fed" healthy human subjects. Both formulations were labeled with a gamma-emitting radionuclide, and their gastric emptying, colon arrival, and in vivo dissolution profiles were monitored using gamma scintigraphy. The standard dosage forms were found to disperse soon after administration and to empty rapidly from both the fasting and the "fed" stomach. The erosion of the controlled-release (CR) system was independent of food. Dosing after a light breakfast altered the gastric emptying profile of the CR formulation and led to significant differences in the plasma levels of levodopa.

Antiparkinson Agents↗

PubMedDate not supplied

A novel application of NMR microscopy: measurement of water diffusion inside bioadhesive bonds.

The self-diffusion coefficient of water (D) inside bioadhesive bonds formed by dry and prehydrated hydrophilic matrices has been spatially resolved using nuclear magnetic resonance (NMR) microscopy. One-dimensional profiles showing the variation of D inside bioadhesive bonds were calculated from nine diffusion-weighted profiles obtained immediately after bond formation and every 5 min for 30 min. The resulting data indicated that the hydration state of a hydrophilic matrix can significantly and dramatically influence the dynamics of water movement inside a bioadhesive bond.

Dehydration↗

PubMedDate not supplied

Self-diffusion and molecular mobility in PVA-based dissolution-controlled systems for drug delivery.

Nuclear magnetic resonance (NMR) microscopy has been used to monitor the hydration of poly(vinyl alcohol) (PVA) samples of varying molecular weight. One-dimensional profiles weighted to predominantly show the variation of water concentration were acquired every 3 min during the first 30 min of hydration and subsequently at 1 and 2 h. Diffusion-weighted profiles obtained after 30 min and 1 and 2 h were used to calculate the spatial variation of the water self-diffusion coefficient. The resulting data provide supporting evidence for the hypothesis that phenomena such as reptation are important near the glassy/rubbery interface of polymers during dissolution, while the diffusion gradually changes to Zimm type near the rubbery/solvent interface.

Diffusion↗