Hydrophilic gel containing nanocapsules of diclofenac: development, stability study and physico-chemical characterization.

The purpose of this work was to develop and to characterize hydrophilic gels containing nanocapsules (NC) of diclofenac (DIC). Nanocapsules suspension of poly-epsilon-caprolactone containing free acid diclofenac were prepared by nanoprecipitation. The pH value of the nanocapsules suspension was 5.70 +/- 0.03 and the mean sizes of the NC were in the sub 300 nm range. Drug incorporated into the nanocapsules was close to 100% and the encapsulation efficiency was 104.1% +/- 3.5%. Diclofenac nanocapsules suspension (1 mg/mL) was incorporated in a Carbopol gel matrix fournishing a formulation with 0.5 mg of DIC/g. The gel stability was evaluated in terms of the macroscopic and microscopic aspect, rheological properties, pH and drug recoveries. As a result, we obtained a suitable formulation for topical use presenting a non-Newtonian behaviour with plastic properties and with intact nanostructures in the gel matrix after 3 months storage atroom temperature (freeze-fracture electron microscopy).

Analytical methods for measuring urea in pharmaceutical formulations.

Two new methods are described for the routine determination of urea that utilize HPTLC-densitometry and colorimetry. The methods involve derivatization of urea with p-dimethylaminobenzaldehyde to a yellow-coloured compound. Validation of the methods was accomplished with respect to linearity, accuracy, reproducibility and limit of detection/quantification. Both methods were compared with an enzymatic method previously described in the literature and were found to be in close agreement. The proposed methods have the advantages of being simple, rapid and involve a single step sample preparation. Under experimental conditions HPTLC was the most sensitive method.