Development and in-vitro evaluation of sustained-release meclofenamic acid microspheres

Preparation and control-release kinetics of isosorbide dinitrate microspheres

Microcapsules for sustained release of poorly soluble isosorbide dinitrate (ISDN) were prepared based on ethylcellulose (EC) and/or blended with appropriate amounts of relatively hydrophilic hydroxypropyl cellulose (HPC) as matrix materials using the oil-in-oil emulsion evaporation method. The microspheres studied had three-mode sizes (100-150, 250-300 and 400-450 microm) and four polymer compositions (1, 0.833, 0.67 and 0.5 weight fraction EC). The microspheres were observed to contain essentially no drug crystalline domain and were of a porous morphology. The cumulative amounts of ISDN releasing from the microspheres as functions of mode fractions size and polymer compositions were measured in vitro. It was observed that the microspheres' size influenced the release behaviour of drug more obviously than the polymer composition. The smaller size and the higher hydrophilic HPC content show the faster release rate of drug and the smaller amount of drug residue. The kinetics of drug release depends on the size and polymer composition. The microspheres with 100-150 microm, of all polymer compositions, present one-stage diffusion kinetic with a lag period for drug release. On the other hand, the microspheres with the other two sizes exhibit two-stage diffusion kinetic with a lag period. According to the kinetic model, the microspheres obtained are surmised to have a core-shell like drug concentration distribution and/or a core-shell morphology.

Formulation and pharmacodynamic evaluation of captopril sustained release microparticles

Cellulose propionate (CP) microparticles containing captopril (CAP) were prepared by solvent evaporation technique. The effects of polymer molecular weight, polymer composition and drug:polymer ratios on the particle size, flow properties, morphology, surface properties and release characteristics of the prepared captopril microparticles were examined. The anti-hypertensive effect of the selected CAP formulation in comparison with aqueous drug solution was also evaluated in vivo using hypertensive rats. The formulation containing drug:polymer blend ratio 1:1.5 (1:1 low:high molecular weight CP), namely F7, was chosen as the selected formulation with regard to the encapsulation efficiency (75.1%), flow properties (theta=24 degrees, Carr index=5%, Hausner ratio=1.1, packing rate=0.535) and release characteristics. Initial burst effect was observed in the release profile of all examined formulations. DSC and SEM results indicated that the initial burst effect could be attributed to dissolution of CAP crystals present on the surface or embedded in the superficial layer of the matrix. The release kinetics of CAP from most microparticle formulations followed diffusion mechanism. After oral administration of the selected microparticle formulation (F7) to hypertensive rats, systolic blood pressure decreased gradually over 24 h compared to reference drug solution. These results may suggest the potential application of cellulose propionate microparticles as a suitable sustained release drug delivery system for captopril.

Combined effect of oleic acid and polyethylene glycol 200 on buccal permeation of [D-ala2, D-leu5]enkephalin from a cubic phase of glyceryl monooleate

The combined use of the lipophilic permeation enhancer, oleic acid together with polyethylene glycol 200 (PEG 200) as a co-enhancer and incorporated into the cubic liquid crystalline phase of glyceryl monooleate was investigated in the ex vivo buccal permeation of [D-Ala2, D-Leu5]enkephalin (DADLE) through porcine buccal mucosa mounted in a Franz cell. The addition of oleic acid (1%) and PEG 200 (1-10%) did not change the intact appearance of the cubic phase. PEG 200 increased the aqueous solubility of oleic acid incorporated into the cubic phase and hence promoted the transport of oleic acid into the porcine buccal mucosa. The solubilising effect of PEG 200 on oleic acid incorporated into the cubic phase was dependent on the PEG 200 concentration but was non-linear. The buccal permeation flux of DADLE significantly increased when 5% (P<0.01) or 10% (P<0.001) of PEG 200 was co-administered with 1% oleic acid compared with the cubic phase containing 1% oleic acid alone. The present results suggest that PEG 200 enhances the action of the lipophilic permeation enhancer oleic acid and that the combination of oleic acid and PEG 200 as a co-enhancer can be a useful tool to improve the membrane permeability in the buccal delivery of peptide drugs using a cubic liquid crystalline phase of glyceryl monooleate and water.