Accelerated stability of Ibuprofen-Eudragit RSPM sustained release tablets, IR and DSC solid stability testing.

Preformulated Ibuprofen-Eudragit RSPM sustained release tablets were subjected to accelerated stability testing at 25, 37 and 45 degrees C for 6 months. The stored tablets were evaluated for the intact drug in the formula, drug-polymer interaction and compatibility of the drug with the formulated excipients using infra red spectroscopy (IR) and differential scanning calorimetry (DSC). The IR spectrum of Ibuprofen in the tablets prepared by 15% w/v Eudragit RSPM as a granulating agent and containing 23% w/v Avicel pH 102 as an excipient is similar to the IR of standard Ibuprofen. There is no change in the IR spectra of the tablet components before and after storage of those tablets at the different investigated temperatures for 1, 3 and 6 months. The DSC thermograms of the Ibuprofen stored tablets show that the drug was still in the highly pure (> 98%) crystalline form and there was no significant degradation after storage indicating the stability of the drug on storage. In detecting Ibuprofen purity in the stored tablets, plotting of the sample temperature versus the reciprocal of the fraction of Ibuprofen melted showed deviation from Van 't Hoff linear plot.

Effect of dimethyl-beta-cyclodextrin on nitrazepam stability.

Nitrazepam was found to form an inclusion complex with heptakis; 2,6 di-O-methyl-beta-cyclodextrin (DM-beta-CD) in solution. The phase solubility diagram was found to be AL type with no precipitation of the inclusion complex formed. The kinetic studies of nitrazepam hydrolysis in DM-beta-CD solution at 30, 40 and 50 degrees C was followed spectrophotometrically, as the degradation products of the drug did not interfere with such assay. It was found that the degradation of nitrazepam in acidic media followed the first order reaction kinetics at the temperatures studied. Inclusion complexation of nitrazepam in DM-beta-CD resulted in a relatively improved stability of the drug in solution at 30 degrees C. On the other hand, no appreciable stabilization was achieved at higher temperatures (40 and 50 degrees C).

Effect of various disintegrants on the availability of directly compressed sulphadimidine tablets.

Sulphadimidine tablets were prepared using 50% w/w of the following vehicles, Celutab, anhydrous lactose and Avicel. Various disintegrants 5% w/w were also incorporated e.g. Primojel, Veegum F, Amberlite, STA-Rx, Meprogat and Alginate YZ. It was found that the disintegration time of the various tablets containing different disintegrants was considerably decreased. The disintegrants increased also the dissolution rate of the various tablet formulations containing sulphadimidine by different extent. The variations in the dissolution rate among the various tablet formulations may be due to the difference in the nature of the disintegrants and their mechanism of action and possibly their interactions with the drug or the vehicle.

Formulation and bioavailability of directly compressed oxytetracycline hydrochloride tablets.

Different tablet formulations containing various vehicles were selected for this study. These tablets were prepared using different proportions of either single or binary vehicles, and were found to possess different disintegration times. A significant correlation was obtained between the dissolution time (T50) and the urinary excretion data as well as their disintegration time. The dissolution rate of the produced tablets therefore can affect their physiological availability which in turn was dependent upon the type of vehicle used and its actual concentration in the formula. Other factors such as the type and concentration of the lubricant(s), hardness values of the tablets prepared, solubility of the drug as well as interactions between the drug and vehicles used may also play a part.

The prolonged release of oxytetracycline hydrochloride from ethylcellulose microcapsules.

Oxytetracycline hydrochloride microcapsules were prepared by separation of ethylcellulose from cyclohexane solution following cooling. Incomplete release was found when testing the dissolution rate in water. Interaction of the polymer with oxytetracycline was elucidated by IR spectroscopy. More release of the drug in water agreed with the diffusional model, but in acid it was more complex.

A study on the release of prednisone from new ointment bases containing various additives.

The effect of various additives on the release of prednisone from new ointment bases, was investigated. It was found that the rate of release of prednisone was greater from the oil in water emulsion ointment base that both the water in oil or oleagenous bases. The incorporation of water in the water in oil emulsion base decreased the rate of diffusion of prednisone than any of the other additives used. It was also concluded that the best release of prednisone was obtained from the bases which were of similar nature to the diffusion medium. Other factors such as the characteristics of bases and the additives as well as their effect upon the solubility of the drug in the mixture may play a part.