Mathematical Modeling of Magnesium Oxide Release from Granules Produced by Laboratory Fluidization

New formulation of in situ gelling Metolose-based liquid suppository

CONTEXT

An in situ gelling liquid suppository is liquid at room temperature but forms a gel at body temperature. In our work, Metolose® SM-4000 (methylcellulose) is studied that basically shows thermal gelation at 68°C (2%, w/w).

OBJECTIVE

The objective was to study the potency of different factors (concentration, pH, additives) to change the value of thermal gelation temperature (T (t)) for Metolose® to form an in situ gelling liquid suppository.

MATERIALS AND METHODS

We studied the effect of Metolose® concentration, pH, and salts (sodium chloride, potassium chloride, sodium hydrogen carbonate, and sodium monohydrogen phosphate) on T (t) by viscosimetry. To choose the appropriate compound, in vitro drug release was examined. Rectal safety test was performed on rats in vivo after 12-hour application.

RESULTS

Increasing the Metolose® concentrations (0.5-4%, w/w), T (t) can be decreased, but it also altered the consistency of gel. pH does not affect the T (t). The water-soluble salts allowed reducing the gelation temperature to 37°C. Sodium monohydrogen phosphate in 4.5% concentration was found to be the most appropriate. The impact of examined factors on in vitro drug release of piroxicam from the in situ-formed gel was characterized according to Fickian diffusion. Metolose® and the chosen salt did not cause any morphological damage on the rectal tissues.

DISCUSSION

According to our study, Metolose® has the physical and chemical potential to be used as base for liquid suppositories.

Study of the theophylline content of single coated particles by gas chromatography/mass spectrometry

The aim of the present study was to determine by gas chromatography/mass spectrometry (GC/MS) the content uniformity of single theophylline microcapsules of different particle size ranges. Microencapsulation was carried out in a laboratory fluidized bed system using Eudragit L30D aqueous dispersion. Scanning electron microscopy was applied for the characterization of the surface morphology of the prepared theophylline microcapsules of two different particle size ranges. The theophylline content of single particles was determined by GC/MS analysis. It was found that the particle size of microcapsules greatly influenced their theophylline content. The GC/MS analysis was successully applied to indicate the changes in the content uniformity and thus the interparticular costing distribution of single theophylline microcapsules in the presence of several excipients.

Mechanistic modeling of drug release from chitosan coated tablets

A mechanistic model for drug release from tablets coated with chitosan was derived, assuming that: (1) core tablets are spherical and the drug dissolution is diffusion dependent. (2) In order for the drug release to occur, dissolution medium penetrates through the coated film and leaches out the drug through the film and the lag-time, t(lag) is set for these processes. (3) The coated film itself dissolves and becomes thinner with time. (4) After the film has completely dissipated and the undissolved core tablet becomes naked, drug release proceeds just as the spherical core tablet. Drug release rate was given as a differential equation. Model adaptation was carried out to the release data of propranolol hydrochloride tablets coated with chitosan and kept in different storage conditions. The goodness-of-fit of our model was better than any other conventional equations tested and estimated model parameters were informative.