[The use of cassava starch in the formulation of gelatin capsules]. / L'utilisation de l'amidon de manioc dans la formulation de gélules.

Cassava, corn and potato starch were, after storage at various conditions of temperature and relative humidity, mixed with a model drug phenacetin. The powder mixtures were filled into hard gelatin capsules. The powder beds containing 20% and 50% starch do not disintegrate within 2 hours. The shortest disintegration time was observed for the mixture containing 80% potato starch. The dissolution rate of phenacetin depends on the porosity of the powder bed filled and the kind of starch used. Potato starch improves the availability of the drug. The disintegration action of corn and cassava starch are almost identical.

A comparative rheological study on carbopol viscous solutions and, the evaluation of their suitability as the ophthalmic vehicles and artificial tears.

The rheological behaviours of different types of Carbopol (Carbopol 940, 934, 941 and 910) were investigated in the present work. Viscous solutions of these polymers were prepared in the range of concentration between 0.01-0.25% (w/w). 10% aqueous solution of sodium hydroxide was used for the neutralization procedure. Mannitol, sorbitol, sodium chloride and borate were tested to make the isotonic solutions. The viscosities of the solutions decreased dramatically with sodium chloride and sodium borate. Mannitol had no effect on the pH values of the solutions while sorbitol has showed a small effect. The solution prepared were sterilized by autoclaving and stored at 4 degrees C for 3 months. The pH value, viscosity and osmolality measurements were made after neutralization and sterilization, at the end of 1 and 2 weeks, 1, 2 and 3 months of storage. It could be concluded that four types of Carbopol are suitable for ophthalmic use. The aqueous vehicles of Carbopol 940 had an excellent appearance and clarity when compared with the other types of polymer.

Relationship between precorneal retention of viscous eye drops and tear fluid composition.

The influence of viscolysers on the precorneal residence of a fluorescent tracer was determined, using slit lamp fluorophotometry. The solution acceptability was evaluated by the volunteers by answering a standard questionnaire. The relationship between precorneal retention of viscous eye drops, discomfort and tear fluid composition after instillation of various cellulosic solutions was examined. Irritating hydroxypropylcellulose solution increases the total protein concentration of tears, without change in the ratio of lysozyme to total protein.

Formulation of Carbopol 940 ophthalmic vehicles, and in vitro evaluation of the influence of simulated lacrimal fluid on their physico-chemical properties.

Carbopol 940 ophthalmic vehicles were prepared in order to investigate the interaction between the simulated lacrimal fluid and the polymer, and to examine the influence of sodium fluorescein - a tracer for the fluorophotometric studies - on the physico-chemical properties of the polymer vehicles. Four kinds of vehicles containing mannitol (5%), sodium fluorescein (0.05%) and disodium edetate (0.01%) were formulated. Physicochemical properties of the preparations including pH, osmolality, surface tension and viscosity were measured after neutralization and sterilization, and also after 1 and 2 weeks, 1, 2 and 3 months of storage at 4 degrees C. The viscosity significantly decreased by adding sodium fluorescein and disodium edetate to Carbopol 940 vehicles. It was observed no significant effect of sterilization and storage on the viscosity, pH and osmolality. Significant change in the flow property of the vehicles was observed when the simulated lacrimal fluid was added. Three concentrations of Carbopol 940 vehicles (0.20%, 0.15% and 0.10%) both containing and not containing disodium edetate were proposed for in vivo evaluation.

Influence of the physicochemical properties and concentration of native and modified potato starch on the release of a hydrophobic drug from hard gelatin capsules.

The influence of the physicochemical properties and concentration of potato starch and sodium starch glycolate on the release of phenacetin from hard gelatin capsules is examined. Smaller quantities of sodium starch glycolate are necessary to improve the disintegration of the encapsulated powder mass and the drug release, compared to blends with potato starch. From the ratio of the absolute particle diameter increase to the mean pore diameter of the encapsulated powder mass no prediction about capsule disintegration could be made, contrary to tablets. A better correlation seems to exist between the total volume increase of the starch grains and the disintegration time of the formulation.

Evaluation of sodium hyaluronate as viscous vehicle for eye drops.

The influence of sodium hyaluronate and hydroxyethylcellulose on the elimination of a fluorescent tracer from the precorneal area of human eyes is investigated using a slit lamp fluorophotometer. The rheological characteristics of the equiviscous ophthalmic solutions are examined. Both viscosity enhancing polymers improve significantly the residence of the tracer in the tear film. The high viscous sodium hyaluronate solution is better tolerated than the hydroxyethylcellulose solution.

[The use of preservatives in skin preparations]. / Der Gebrauch von Konservierungsmitteln in Dermatica.

Dermatological preparations may be contaminated during their manufacture and their use. On account of the danger of this contamination, different Pharmacopoeia prescribe the maximal allowable number of microorganisms in the different dermatological preparations. The preservatives used must kill or diminish their number in a period of time equal to the time elapsed between two applications. This time however could be different for each preparation. Therefore the preservatives must have antibacterial activities adapted to the use of the dermatological preparation. The activity can be given by the D-value or the decimal reductiontime. The D-values of the different kinds of dermatological preparations have been calculated with a startcontamination of 10(6) microorganism g. The activity of a preservative must be determined directly in the preparation. Firstly the preparation with a preservative is contaminated with microorganisms, secondly the killing rate is determined and finally the D-value is calculated. After the calculation of the D-value of different samples each containing a different preservative and several concentrations, it is possible to select a preservative and to determine his concentration giving a D-value corresponding to the D-value required by the use of the dermatological preparation.