Microencapsulation of hydroxyzine HCl by thermal phase separation: in vitro release enhancement and in vivo pharmacodynamic evaluation.

The systemic effect of hydroxyzine hydrochloride following its oral administration or topical application is associated with non compliant anticholinergic effect. Subsequently, the present study aims to prepare microcapsules loaded with hydroxyzine hydrochloride enabling its controlled release into the skin and reducing the side effect of its systemic absorption. The microcapsules were prepared by thermal phase separation method using ethyl cellulose/cyclohexane. Optimization of the formulation parameters was carried out by: (1) varying the type and the concentration of the coacervation inducer with microcapsules prepared with three different core: wall ratios, (2) by using ethyl cellulose with two different viscosities, (3) and by the addition of pore inducers such as pregelatinized starch and sucrose in order to enhance the drug release. Microcapsules of 99% encapsulation efficiency were prepared using 1% w/v polyisobutylene, and 1:0.1 core: wall ratio. The highest percent of drug is released after 9 h from microcapsules prepared using 1:0.1 core :wall ratio. Almost 100% drug was released after 3 h, from the same microcapsules prepared with pregelatinized starch that acts as a core coated with the drug. The pharmacodynamic effect of the chosen preparation was tested on the shaved back of histamine sensitized rabbits. Histopathological studies were driven for the detection of the healing of inflamed tissues.

In vitro and in vivo evaluation of hydroxyzine hydrochloride microsponges for topical delivery.

Hydroxyzine HCl is used in oral formulations for the treatment of urticaria and atopic dermatitis. Dizziness, blurred vision, and anticholinergic responses, represent the most common side effects. It has been shown that controlled release of the drug from a delivery system to the skin could reduce the side effects while reducing percutaneous absorption. Therefore, the aim of the present study was to produce an effective drug-loaded dosage form that is able to control the release of hydroxyzine hydrochloride into the skin. The Microsponge Delivery System is a unique technology for the controlled release of topical agents, and it consists of porous polymeric microspheres, typically 10-50 µm in diameter, loaded with active agents. Eudragit RS-100 microsponges of the drug were prepared by the oil in an oil emulsion solvent diffusion method using acetone as dispersing solvent and liquid paraffin as the continuous medium. Magnesium stearate was added to the dispersed phase to prevent flocculation of Eudragit RS-100 microsponges. Pore inducers such as sucrose and pregelatinized starch were used to enhance the rate of drug release. Microsponges of nearly 98% encapsulation efficiency and 60-70% porosity were produced. The pharmacodynamic effect of the chosen preparation was tested on the shaved back of histamine-sensitized rabbits. Histopathological studies were driven for the detection of the healing of inflamed tissues.