This study describes the in vitro/ex vivo buccal release of chlorhexidine (CHX) from nine mucoadhesive aqueous gels, as well as their physicochemical and mucoadhesive properties: CHX was present at a constant 1% w/v concentration in the chemical form of digluconate salt. The mucoadhesive/gel forming materials were carboxymethyl- (CMC), hydroxypropylmethyl- (HPMC) and hydroxypropyl- (HPC) cellulose, alone (3% w/w) or in binary mixtures (5% w/w); gels were tested for their mucoadhesion using the mucin method at 1, 2 and 3% w/w concentrations. CHX release from different formulations was assessed using a USP method and newly developed apparatus, combining release/permeation process in which porcine mucosa was placed in a Franz cell. The combination of HPMC or HPC with CMC showed slower drug release when compared to each of the individual polymers. All the systems proved suitable for CHX buccal delivery, being able to guarantee both prolonged release and reduced transmucosal permeation. Gels were compared for the release of previously studied tablets that contained Carbopol and HPMC, alone or in mixture. An accurate selection and combination of the materials allow the design of different pharmaceutical forms suitable for different purposes, by simply modifying the formulation compositions.
Abstract. The purpose of this research was the preparation of four formulations containing hydrocortisone acetate (HCA) for topical application, including two aqueous systems (hydrophilic microemulsion and aqueous gel) and two systems with dominant hydrophobicity (hydrophobic microemulsion and ointment). The formulations were tested for the release and permeation of HCA across an animal membrane. The release of HCA was found comparable for the four systems. The two microemulsions promote permeation across an ex-vivo membrane, examined by means of a Franz cell. Hydrophobic microemulsion guarantees the highest solubility (2,370 μg/ml) and flux (133 μg/cm 2 .h) of the drug, since it contains almost 40% Transcutol, a permeation enhancer. Gel and ointment provide lower solubility and flux, being the values, related to the ointment, the lowest ones (562 μg/ml and 0.4 μg/ cm 2 .h). Experimental results allow the conclusion that gel and ointment can be suitable when it is desirable to minimize absorption of topically applied HCA as to keep the drug restricted to the diseased area and prevent side effects of the systemic presence of HCA.
The antimycotic imidazole derivative clotrimazole is employed locally for the treatment of genitourinary tract mycotic infections and is formulated as creams, foams, tablets, gels, irrigations, or pessaries. In this study, a new dosage form was developed by including bioadhesive polymers (polycarbophyl, hydroxypropylmethylcellulose, and hyaluronic sodium salt) into pessaries made of semisynthetic solid triglycerides. These polymers hold the delivery systems in the vaginal tract for a few days without any toxic effects or important physiological modifications, prolonging the permanence of the drug on the vaginal mucosa. Technological controls (compatibility with differential scanning calorimetry [DSC] studies, particle size analysis, and liquefaction time test) and biopharmaceutics studies for the evaluation of the release of the drug from the dosage form and of the bioadhesive properties were carried out. Moreover, a new test for the evaluation of the permanence of the drug in a simulated application site was developed from a modification of the Satnikar and Fantelli method for the evaluation of the liquefaction time of rectal suppositories. This test simulates the physiological vaginal condition and verifies the efficiency of the polymers in prolonging the permanence of the dosage form in the location where it is applied. The technological controls demonstrated that the presence of the polymers did not have an influence on the characteristics of the pessaries. On the other hand, there was an improvement in adhesivity of the pessaries in the in vitro adhesion test and prolonging of the liquefaction time in the liquefaction time test in the presence of mucoadhesive polymers, which increased with increasing polymer concentration. The presence of the mucoadhesive had a large influence on the permanence of the drug in the simulated application site because it modified the distribution of the drug along the simulated application site. In conclusion, the developed new formulations showed good technological and adhesion properties and the capacity of hold the dosage form in the target site. Among the employed bioadhesive polymers, the best behavior in the performed test was by polycarbophyl at its maximum concentration.
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