Entrapment of Phenytoin into Microspheres of Oleaginous Materials: Process Development and in Vitro Evaluation of Drug Release

Effect of hexacosanol on the characteristics of novel sustained-release allopurinol solid lipospheres (SLS): factorial design application and product evaluation

This investigation involved the evaluation of the effect of hexacosanol (HC, ceryl alcohol), a new hydrophobic wax modifier (WM) in comparison with conventional modifiers, on the development of sustained-release allopurinol (AP) solid lipospheres (SLS) intended for use in a suspension formulation and other oral dosage forms. Various beeswax (BW)/WM blends (composition ratio 1:1) were thus used to prepare SLS by a modified oil-in-water emulsion meltable disperse-phase (MDP) encapsulation method without using organic solvents and the influence of these blends on the drug encapsulation efficiency (EE), size distribution and the time for 50% of the drug to be released (t50%) was investigated. Results indicated that incorporation of HC in wall matrix of SLS provided the means to enhance the EE of AP and to modulate the rate of drug release into dissolution media (simulated gastric fluid (S.G.F.: pH 1.2) and simulated intestinal fluid (S.I.F.: pH 7.4). The effects of the process variables; HC concentration, dispersant (pluronic F-68: PF-68) concentration and drug:wax ratio were also studied on the properties of AP-loaded SLS by a 2(3) factorial design. The EE values were in the range of 80.8-92.67%. The only significant parameter affecting (P<0.01) the size and size distribution of the SLS formulations was the amount of the PF-68, whereas the factor with the biggest influence (P<0.05) on the drug EE was the initial loading of AP (in terms of the drug:wax ratio). The amount of HC blended with wax and the initial drug loading significantly (P<0.01) affected the t50% values of all of the formulations. The release of AP was more extended (t50% values (S.I.F.; pH 7.4)=9.91-25.36 h, depending on the drug:wax ratio) and surface morphology of SLS was improved with higher HC content (15%, w/w) formulations. The release patterns fitted the Baker-Lonsdale dissolution kinetics for spherical matrices. A significant decrease of plasma uric acid levels (P<0.05) and hepatic impairment in male rats was observed after oral administration of a SLS (mean size: 120 microm) suspensions of the optimum formulation, compared to suspensions of pure AP.

A new delivery system of clobetasol-17-propionate (lipid-loaded microspheres 0.025%) compared with a conventional formulation (lipophilic ointment in a hydrophilic phase 0.025%) in topical treatment of atrophic/erosive oral lichen planus. A Phase IV, randomized, observer-blinded, parallel group clinical trial

BACKGROUND

Topical application of clobetasol-17-propionate has been diffusely reported as an efficacious therapy in atrophic/erosive oral lichen planus (OLP), without exposing the patient to systemic side-effects. However, prolonged contact and respective topical effects on the oral mucosa should be avoided.

OBJECTIVES

The aim of the present study was to evaluate efficacy and compliance of new lipid microspheres loaded with 0.025% of clobetasol propionate (formulation A) compared with a commonly used formulation (a sort of dispersion of a lipophilic ointment in a hydrophilic phase) with the same amount of drug (formulation B) in the topical treatment of OLP.

PATIENTS AND METHODS

Fifty patients with symptomatic OLP were enrolled in a controlled single-blind phase IV clinical trial. After a dropout of five patients, a total of 45 patients [12 males and 33 females; mean age 61.1 years (+/- 12.3 SD; range 25-82)] were treated (17 with formulation A and 28 with formulation B, matched for gender and age; P > 0.2) with the same dosage regimen. At times T0, T1 and T2 we evaluated the following parameters: (i) pain score (by linear visual analogue scale; 0-100); (ii) clinical score; (iii) clinical resolution; and (iv) patient compliance. Statistical analysis was calculated using S-Plus 4.0 and SPSS 9.0 (Student's t-test, chi(2), Kolmogorov-Smirnow, Friedman, Student-Newman-Keuls, Mann-Whitney U-test and Spearman tests).

RESULTS

Both formulations were found to be similar for parameters ii, iii and iv, although with a better general trend for formulation A; a significant difference was registered for formulation A in terms of a reduction in painful symptoms (parameter i) at time T2 (P = 0.02).

CONCLUSIONS

Our results suggest that the new topical drug delivery system (formulation A) may enhance, at least in terms of symptom remission and compliance, the effectiveness of clobetasol propionate at a dose of 0.025% in OLP therapy.

Trehalose-hydroxyethylcellulose microspheres containing vancomycin for topical drug delivery

A new formulation, in which vancomycin is entrapped into trehalose and hydroxyethylcellulose (Natrosol) spherical matrices, is described. Microspheres were produced by the solvent evaporation method. The entrapped drug was fully recovered following microspheres dissolution. Differential scanning calorimetry analyses proved that Natrosol maintains trehalose in its amorphous form. The stabilizing effects of trehalose on vancomycin were evaluated even after long storage and heating of microspheres. Calorimetric data indicated no decomposition of the entrapped drug. In vitro drug release, already performed by using a general two-compartment linear time-invariant open model, suggests that the new delivery system is suitable for topical application on extensive and purulent or burn wounds, when the skin is heavily damaged and the barrier disrupted. The system activation is determined by osmotic phenomena. The prepared new delivery system seems to have characteristics suitable for topical applications on extensive and purulent wounds. The system is able to take away serous exudates from wounds, thus letting the matrix to swell and form a viscous gel-like dispersion that, in turn, enables drug diffusion.