[Studies on gelatin microsphere loaded ligustrazine hydrochloride for lung targeting]

The effect of ligustrazine hydrochloride (LTH) on depressing pulmonary artery hypertension has been proved in recent studies. In an attempt to prepare a lung targeting dosage form, ligustrazine hydrochloride gelatin microspheres (LTH-GMS) were prepared by the method of emulsion process, using 2:1 as the weight ratio of LTH to gelatin. The preparation technique was optimized and the appearance, particle size and size distribution, LTH content, in vitro release, stability, and in vivo distribution of LTH-GMS were studied. The results showed that the mean diameter of LTH-GMS measured by Coulter counter was 12.65 microns, 87.5% of the microspheres ranging from 5 to 24.9 microns. The average content of LTH in LTH-GMS was 16.49% +/- 0.49% (n = 3) with an average extent of entrapment of about 89% and the LTH-GMS were stable for three months when stored in refrigerator or at room temperature. The release profile in vitro (pH 7.8-8.0 phosphate buffer) can be described by first-order kinetic equation. The release t1/2 of LTH when given LTH-GMS was about 6 times as much as that of original LTH. The relative distribution percentage of LTH-GMS in lung when determined 20 min after iv administration to mice was significantly higher than those of LTH-GMS in other tissues and blood, and was about 6 times as much as that of the LTH solution control group in lung under the same conditions.