Time and temperature dependence of disintegration and correlation between dissolution and disintegration rate constants

Granulation by roller compaction and enteric coated tablet formulation of the extract of the seeds of Glinus lotoides loaded on Aeroperl 300 Pharma

The purpose of this research was to improve the hygroscopicity and poor flow properties of the crude dry extract of the seeds of Glinus lotoides and improve the disintegration time of the core-tablets for enteric coated formulation thereof. The liquid crude extract of the plant was adsorbed on granulated colloidal silicon dioxide (Aeroperl 300 Pharma) at 30% w/w and the dry extract preparation (DEP) was dry-granulated with roller-compaction using Micro-Pactor. Hygroscopicity, flow property and disintegration time were improved significantly due to the adsorption and granulation processes. Moreover, the DEP does not become mucilaginous even at higher relative humidity levels (above 65%). Oblong tablets (20 x 8.25 mm) containing 947 mg of the granulated DEP (equivalent to the traditional dose), 363 mg of Avicel PH101 and 90 mg of Ac-di-Sol as disintegrant were formulated using an instrumented eccentric tablet machine at 20 kN. The tablets showed a crushing strength of 195 N, a friability of 0.4% and disintegrated within 9 min. The tablets were then enteric coated using polymethacrylate co-polymers (Eudragit L 100-55 and Kollicoat MAE 100P). The coated tablets resisted disintegration or softening in simulated gastric fluid for a minimum of 2 h and disintegrated within 15 min in intestine simulated fluid at pH 6.8. In addition to controlling the release of the active agents, the enteric coating improved the strength and decreased friability of the core-tablets.

Rational Estimation of the Optimum Amount of Non‐Fibrous Disintegrant Applying Percolation Theory for Binary fast Disintegrating Formulation

The purpose of this study was to propose a method of determining the exact value of disintegrant ratio in a binary drug-disintegrant compacted mixture for a minimum disintegration time in the case of spherical particles. Disintegration is a limiting factor in dissolution process of compact for low water soluble active ingredients. As disintegration time is shortest at a certain ratio of disintegrant, a calculation of this value is important for solid dosage from design to enhance disintegration and dissolution process. According to percolation theory, a minimum disintegration time corresponds to the formation of a continuous water-conducting cluster through the entire tablet. The critical volumetric ratio at which the cluster is formed is named percolation threshold and has the value of 0.16 for random close packed (RCP) sphere systems. RCP systems where chosen as the best model for compacts consisting of spherical particles. Two cases for water diffusion through the tablet were identified, according to geometrical considerations between disintegrant and drug particles. These cases determine if disintegrant particles can have a contact between each other within the compact and thus if porosity and disintegrant volume are included in the continuous cluster. An equation for both cases is presented in the form of piecewise function to determine the minimal disintegrant volumetric ratio for a binary drug/disintegrant compact in order to achieve a minimum disintegration time. Disintegration tests were performed with tablets at different ratios of modified corn starch mixed with caffeine or paracetamol powders. Estimated and experimental optimal ratio were compared showing coefficient R(2) = 0.96.

Correlation and prediction of moisture-mediated dissolution stability for benazepril hydrochloride tablets

PURPOSE

This report investigated dissolution stability of benazepril hydrochloride tablets.

METHODS

Reduction in dissolution rate was observed for benazepril hydrochloride tablets when they were subjected to stressed storage condition (40 degrees C/75% RH) for prolonged periods of time (1-3 months). Moisture contents of initial and stressed tablets were measured by Karl Fischer method. Comparative thermal and physical characterizations of initial and stressed tablets were also performed. A mathematical model that was used to predict possible reduction in dissolution rate was proposed and validated using experimental data.

RESULTS

It was found that there was a direct correlation between moisture content of benazepril hydrochloride tablets and their percentage of dissolution at 10 min. At moisture content below 3.5%, there were no significant changes in dissolution values. Beyond that point, however, a close to linear decrease in dissolution was observed as a function of increase in moisture content. Results from thermal and X-ray analysis have ruled out possible changes in drug substance. Other physical characterization, such as scanning electron microscope and mercury porosimetry measurements, revealed changes in core structure of stressed tablets vs. initial tablets. Based on results from these measurements, "preactivation" of disintegrant was identified as the mechanism for reduction in dissolution rate above critical moisture content. A simple physical model for moisture uptake of benazepril hydrochloride tablets was also proposed for predicting when, based on water vapor transmission and critical moisture content, dissolution rate will decline.

CONCLUSIONS

Physical changes of tablets mediated by moisture were the main cause for reduction in dissolution. Inclusion of desiccant, although beneficial, cannot prevent reduction in dissolution completely. The simple physical model proposed in this report was found to be useful in predicting the dissolution stability of the dosage form.

Effect of lubricant level and applied compressional pressure on surface friction of tablets

A method for measuring friction coefficients of compacted surfaces (tablet surfaces) is described. Frictional coefficient measurements were carried out at various tableting compression forces. The effect of magnesium stearate concentration was found to be a log-linear approach to an asymptote (which would represent a minimum frictional coefficient).

Studies on different dissolution models. IV. Erosion of tablets

A comparative study of the action of erosion on non disintegrating theophylline tablets was performed in the three USP XX dissolution models, the rotating basket, the paddle and the modified disintegration apparatus, as well as in a new (sandwich) model. The results show erosion to be dependent on the mechanical strength of the tablets and to be promoted by the phenomenon of softening of the tablets during the process of dissolution. A considerable and moderate erosion was found for 'soft' tablets in the rotating basket and disintegration apparatus, respectively, whereas no or only slight erosion was observed in the paddle and sandwich models. The phenomenon of dissolution intensified erosion and erosion intensified dissolution is shown to affect the description of the release profiles. The dissolution profiles of the 'hard' tablets in the models preferred to be described by the square root equation, whereas the profiles of the 'soft' tablets in the case of erosion showed a tendency to a better fit with the cube root of mass versus time relation.

Automated dissolution testing of combination drug product using high-pressure liquid chromatography

An automated high-pressure liquid chromatographic (HPLC) system compatible with any standard tablet dissolution apparatus was developed. This system allowed the individual drug concentrations within a product to be determined simultaneously, even when the drugs had similar structures and UV spectra. This automated system permitted unattended sampling and concentration determination at predetermined time intervals. The dissolution medium was pumped continuously through a fixed-volume, microprocessor-controlled injector and returned to the USP rotating-basket dissolution apparatus. No corrections for the changing dissolution medium volume were necessary since each injection onto a reversed-phase HPLC column consumed just 10 microliter of medium. Dissolution tests were performed on three brands of trisulfapyrimidines tablets. Sample injections were made automatically at 5.1-min intervals for approximately 2 hr. Dissolution profiles were determined for each drug in each product. Statistically significant differences were found in the mean concentration-time values between drugs within a drug product and between the drug products.