Histological toxicity study of subcutaneous in situ gel

Materials

Male Wistar rats, normal saline solution, gel formulation, hematoxylin-eosin stain, microtome, paraffin, compound microscope.

Procedure

• Twenty four male Wistar rats weighing between 190-225g are used as test animals. They are divided into two groups.

Group-I:Control Gr:Physiological saline 0.3ml

Group-II:Test Gr:In situ gel formulation 0.3ml

• The formulations are given subcutaneously. The rats are sacrificed at 1st, 7th and 14th day after the begining of the study.
• The subcutaneous tissue at the injection site is separated and fixed by 10% formalin solution for three days. The fixed subcutaneous tissue is embedded in paraffin and sliced into 3micron thin slices.
• To evaluate the inflammatory reaction at the site of injection, the comparison of the numbers of neutrophils, eosinophils and macrophages between Group-I and Group-II is performed. Neutrophils and eosinophils are counted in hematoxylin-eosin stained sections. Macrophages are counted in immunohistolchemical staining sections.

References 

Xin, C., Lihong, W., Qiuyuan, L., Hongzhuo, L., 2014. Injectable long-term control-released in situ gels of hydrochloric thiothixene for the treatment of schizophrenia: Preparation, in vitro and in vivo evaluation. International Journal of Pharmaceutics 469, 23–30.

Dissolution study of polylactic acid based in situ gels

Dissolution study of polylactic acid based in situ gels [prolonged release for 12 days]

In situ gel delivery systems become viscous when the solution is immersed in dissolution medium (or body fluid) at body temperature. The gel may take very long time to get completely dissolved, thus slowly releasing the drug.

Materials

USP Dissolution rate test apparatus, graduated pipette (2ml cap.), phosphate buffer solution (pH 7.4), sodium azide, 

Procedure

• Gel formulation of 10 ml is taken in a small porcelain or glass cup and placed at the bottom of  a USP-2 dissolution rate test apparatus (paddle type). The round bottom jar is filled with 900ml phosphate buffer (pH7.4). Temperature is maintained at 37⁰C. 
• For a prolong released product the time of dissolution may require 12 days or more. In such case, to prevent bacterial growth, sodium azide (final concentration in the 900 ml dissolution medium 0.02%w/v  ) is used.
• The paddle speed is fixed at 50 rpm. Sample (1ml) is collected from the dissolution medium at 1, 3, 6, 9, 12 days interval. After each sampling the round bottom beaker is replenished with 1ml of fresh dissolution medium pre-warmed at 37⁰C.
• The samples are filtered by centrifugation and finally analyzed with HPLC.

References

Xin, C., Lihong, W., Qiuyuan, L., Hongzhuo, L., 2014. Injectable long-term control-released in situ gels of hydrochloric thiothixene for the treatment of schizophrenia: Preparation, in vitro and in vivo evaluation. International Journal of Pharmaceutics 469, 23–30.