Formulation and preparation of a nitrendipine submicron emulsion

The aim of the present study was to enhance the solubility and develop stable parenteral submicron emulsion for the delivery of nitrendipine (NTD). The nitrendipine submicron emulsion (NTDSE) was prepared using egg lecithin, soybean oil, medium-chain triglyceride and oleic acid. They were mixed evenly and processed by homogenization. The influence of formulation variables, such as the change of the proportion of MCT and LCT, amount of emulsifiers and pH, were studied and optimized formulations were developed. Factors affecting preparation procedures including homogenization and thermal sterilization were fully investigated. Particle size of the submicron emulsion was evaluated by laser diffraction and ζ-potential was measured by Zeta potential analyzer. The stability studies were conducted at 25 ± 2˚C and 6 ± 2˚C. The optimum formulation consists of NTD 0.1% (w/v), MCT 5% (w/v), LCT 5% (w/v), egg lecithin 1.2% (w/v), F68 0.3% (w/v), oleic acid 0.03% (w/v) and glycerol 2.5% (w/v). NTDSE was prepared by a piston-gap homogenizer with homogenization pressure at 1000 bar for 6 cycles. The product can resist steam sterilization at 121˚C for 15 min. Results showed that stable NTDSE was developed with a mean size of 154 ± 21 nm and a Zeta potential of –26.35 mV. The submicron emulsion can maintain stable for at least 6 months at 25˚C and 9 months at 6˚C. The study demonstrated that NTDSE was successfully prepared with stable physicochemical properties. In addition, the submicron emulsion can undergo at least 9 months stored at 6˚C without light.