Synopsis A new gelification process of vegetable oils was developed using a cellulose derivative in order to obtain transparent oleogels (anhydrous gels based on fatty components) of different consistencies. The study of their structure has been carried out by infra-red spectroscopy, differential thermal analysis and X-ray diffractometry. All these physical tests have demonstrated the gel structure of the formulations. Finally, a rheological study was run to elucidate their specific properties and their stability during storage.

Synopsis A gelling process for glycerides (synthetic or natural) by a cellulose derivative has been developed to obtain transparent oleogels of different consistencies. The present work examines the rheological behaviour of these oleogels. The study was carried out with a Trombomat Viscosity Follower. This measurement system allowed the determination of the gelling time and viscosity changes as a function of temperature.

Synopsis Benzoyl peroxide has been used for over 20 years to treat youthful acne. The aim of this study is to determine its release rate from the vehicle that allows it to reach and treat the skin (topical availability) and its ability to pass through the skin and reach the general circulation (bioavailability), in order to bring about good topical availability, linked to bioavailability or, an 'abioavailability'. Three preparations containing 10% of benzoyl peroxide were administered to the back of shaven New Zealand rabbits. At day 0, day 5, day 12, day 19, day 26 and day 33, the topical effects were measured by cutaneous temperature, degree of erythema and the benzoic acid plasma record card, which shows blood sample results of the metabolism of the drug. The results obtained show that the topical availability of benzoyl peroxide coincides with a decrease in cutaneous temperature, after application in various dosage forms, in spite of the appearance of a marked erythema. The bioavailability is demonstrated by plasma benzoic acid evaluation. Before administration, benzoic acid levels are low but increase half an hour after administration, to reach a maximal level at 3 h. Benzoyl peroxide metabolizes quickly and does not seem to be able to cross the skin without being changed.

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In order to evaluate the influence of food and time of administration on the absorption of diethylamine chromocarbe, a bioavailability study was performed in 8 volunteers by using a new method of plasmatic drug evaluation. The results obtained indicate that lunch has little effect on diethylamine chromocarbe absorption in comparison with the administration 0.5 h before breakfast. The bioavailability parameters Cmax, tmax, and AUC are not statistically different and the two methods of administration can be considered as bioequivalent. The absorption of diethylamine chromocarbe seems to be reduced when the drug is administered before dinner. This delay on absorption may be due to circadian rhythm of tractus gastrointestinal absorption or to the reduction of physiological activity of volunteers.