Study On The Nanosuspensions Of A Long-acting Derivative Of Riboflavin

The problem of poor solubility is very common among 40% of drug candidates at present and the poor solubility would like to cause the low bioavailability of drugs. This also leads to the R&D failure of many efficient drug candidates. Development of delivery systems of drugs with poor solubility is a large challenge to the pharmaceutical research. As a paradiam of solutions of the problem mentioned above, long-acting derivative of riboflavine was selected as the model drug and its nanosuspension injection was studied in this paper. The physical-chemical characteristics of long-acting derivative of riboflavine were investigated, and it was found that it had poor solubility. The whole study was decribed as follows in details.1. Study before the formulationThe content of long-acting derivative of riboflavine was determined by ultraviolet spectrophotometry. Its solubility and oil/water partition coefficient were also determined. The results showed that its oil/water partition coefficient was large. It meant that long-acting derivative of riboflavine was amphipathic and more liposolubility. As a result, long-acting derivative of riboflavine was appropriate to be prepared as nanosuspensions.2. Formulation screening and technology optimizationAfter the formulation screening and technology optimization, the solvent injection was selected as the preparation method. The nanoparticles structrures of long-acting derivative of riboflavine was nanotubes, the size 280nm and the zeta potential -24.5mv. Freezing and freeze drying didn't destroy the structure. After freeze drying, the long-acting derivative of riboflavine nanosuspensions were yellow powder and dispersed with water to form uniform, stable nanosuspensions before injection.3. Establishment of analysis methodThe sensitive and accurate in vitro and in vivo HPLC methods of long-acting derivative of riboflavine and riboflavin were established respectively. The in vitro HPLC method of long-acting derivative of riboflavine was as follows: the mobile phase methanol:water=87:13(V/V), flow rate 1.0ml/min, t_R=6.66min, detection wavelength 269nm. The in vitro HPLC method of riboflavin was as follows: the mobile phase methanol:1.0%HAc=45:55(V/V), detection wavelength 267nm. The in vivo HPLC method of long-acting derivative of riboflavine was as follows: the mobile phase methanol:water=84:16(V/V), flow rate 1.0ml/min, detection wavelength 269nm. The in vivo HPLC method of riboflavin was as follows: the mobile phase methanol: 1.0%HAc=40:60(V/V), detection wavelength 267nm.4. Physical and chemical characteristicsThe size distribution of nanoparticles wasn't affected by high speed centrifugalization, animals' plasma and Co⁶⁰ irradiation. Buffer and boiling sterilization influenced the nanoparticles size easily. Sterilization with high pressure destroyed the structure of nanoparticles thoroughly and influenced the stability. Long-acting derivative of riboflavine nanosuspensions was stable in neutral conditions (pH7.4), and degraded into riboflavin easily in acid and alky conditions. The degradation rates in different biological systems, such as enzymes and plasma, wre higher than that in buffer systems. The degradation t_1/2 in healthy adult plasma was 286.17h.5. StabilityThe influence factors of long-acting derivative of riboflavine nanosuspensions were studied. The freeze drying powder was sealed into the brown glass bottle. Then rubber bung and aluminium can was packaged. Till now, the accelerated test and the long time test showed that long-acting derivative of riboflavine nanosuspensions powder was stable.6. PharmacodynamicsThere were two model animals in the pharmacodynamic. The methotrexat (MTX) was used to determine the prevention effect of long-acting derivative of riboflavine. The result showed that long-acting derivative of riboflavine was preventive to the angular cheilitis caused by injection of high dose MTX. Riboflavin deficiency feeds was prepared and the riboflavin deficiency model rats was established to determine the cure effect of long-acting derivative of riboflavine. The result showed that long-acting derivative of riboflavine had obvious long time effect. Single injection could sustain for more than 30 days. Every monitoring index of cure group was better than that of riboflavin deficiency group. It showed that long-acting derivative of riboflavine had good therapeutic effect.The long-acting derivative of riboflavine nanosuspensions of high concentration was prepared successfully by novel nanotechnology and stable physically and chemically. It could degraded into riboflavin easily in vitro. Moreover, it could be dispersed with water and freeze dried. This solved the problems of traditional preparations.