The Preparation And Properties Of Solide Dispersion Based On Insoluble Esters Pesticides

Solid dispersion is a highly dispersed solid dispersion system prepared by the mixture of drugs and carriers.In recent years, solid dispersion technique has been used to improve the solubility and dissolution rate of insoluble drug. In this paper,the solid dispersion, solubilization, dissolution behavior of the solid dispersion complex between carrier material polyethyleneglycol (PEG),polyviny lpyrrolidone(PVP)and hard soluble esters pesticides (avermectin,indoxacarb, cyhalothrin)were studied.The aim is to use solid dispersion technology to improve the solubility and dissolution of hard soluble esters pesticides.Firstly, solvent-melting method and solvent method were respectively used to prepare the three technical material PEG solid dispersions and the PVP solid dispersions.The impact on the solubility and dissolution rate of technical materical in the solid dispersions were discussed by the amount of carrier material and technical material,thereby selecting the best drug load ratio.Results the optimal weight ratio of avermectin and PEG(6000,20000),PVP wasl:10;indoxacarb and PEG (6000,20000), PVP was 1:6;cyhalothrin and PEG (6000,20000), PVP was 1:10.Secondly,the structure of solid dispersions was characterized by Ultra Violet spectra(UV), Fourier transform infrared spectroscopy(FTIR),Scanning electron microscope(SEM), X-ray powder diffraction(XRD).The results showed that the technical material was in the amorphous state or molecular in the solid dispersion. This also can confirmed that the technical material and PEG6000, PEG20000 occurred physical effect, which form encapsulated object. The hydrogen bond interaction may occur between technical material and PVP in PVP solid dispersion.Once again,study solubilizing properties on technical material using different solid dispersions.Solubility tests showed that solubility enhencement of technical material in physical mixture and solid dispersion can be achived by using PEG6000,PEG20000,PVP.The solubility of avermectin in solid dispersions(21.7957,24.9970,28.3231 mg/L) was significantly increased than those of avermectin (0.0078 mg/L) and the simple mixture of avermectin with carrier(1.2469,1.4604,3.807mg/L).The solubility of indoxacarb in indoxacarb-PEG6000,PEG20000,PVP solid dispersion was increased by 30,10.6, 45.5 times.In regard to cyhalothrin, the results were 3552,4256,5635 times.Whereby with increasing molecular weight of PEG, the solubility of avermectin and cyhalothrin also increased, while the solubility of indoxacarb is decreased in solid dispersion. Compare PEG with PVP,the solubilization of PVP was the most obvious. The solubilization of PEG was related to the hydrophilic property of the carrier material,with the increase of the molecular weight of the carrier material, the hydrophilicity decreases,the hydrophilicity of the material in descending order was PEG6000, PEG 20000; While the solubilization of the principle of PVP is that the hydrogen bond interaction which occured between technical material and PVP in PVP solid dispersion made technical material highiy dispersed in the carrier to achieve the purpose of solubilization.Then,dissolution behavior of solid dispersions was discussed.Dissolution testing showed that:Compared with the three technical material, the dissolution of the three technical material in PEG,PVP solid dispersion significantly improved.Generally speaking, the dissolution degree increases with the increase of the solubility.Illustrated by the case of avermectin dissolution rate was above 90% after 24 hours in PVP solid dispersion,which increased 3 times.In conclusion,the drug-loaded systems were made into corresponding formulations,toxicity of orresponding formulations were studied.Toxicity tests showed that when the amount of 15g.ai/acres, the avermectin solid dispersion can play insecticidal effect.Compared with conventional avermectin microemulsio,solid dispersion granules showed a superior insecticidal effect microemulsion. When using indoxacarb-PEG granules and indoxacarb-PVP granules in an amount of 15 g.ai/acres, the corn borer mortality was 32.2% and 35.1%,which showed higher insecticidal rate.When the dosage is 15g.ai/acres, the comparison of the insecticidal rate was the cyhalothrin-PVP granules> cyhalothrin-PEG granules> cyhalothrin microemulsion agent.All of the above show that the insecticidal effect in the solid dispersion preparation is superior to the conventional dosage form.