Studies On Preparation And Efficacy Of Mequindox Nanoemulsion

Objective: Mequindox has good curative effect to yellow and white scour of pigletscaused by Escherichia Coli but few formulations with relative low bioavailability, and isdifficult to be administered to piglets. For these reasons, this research developed mequindoxnanoemulsion (M-NE) as a novel transdermal drug to treat piglets with yellow and whitescour.Methods:(1) Preparation and quality investigation of M-NE: The optimum oil phasewas selected by its soluble ability to mequindox，and the optimum surfactant was determinedby the area of pseudoternary phase diagrams， and the M-NE was prepared by phasetransformation. The structure pattern of M-NE was identified by staining, and the shape anddistribution of M-NE droplets were surveyed by transmission electron microscope, and itspartical size and polydispersity index (PDI) were measured by Zetasizer Nano ZS instrument.(2) Stability investigation of M-NE: The stability of M-NE was evaluated by Zeta potentialwhich was measured by Zetasizer Nano ZS instrument, temperature test, high-speedcentrifugal test and accelerated test. The period of validity of M-NE was determined by long-term test.(3) Safety evaluation of M-NE: The skin acute toxicity and skin irritation wereevaluated by administering M-NE to the hairless skin of rats.(4) Efficacy research of M-NE:The transdermal permeability was determined by test utilizing mice skin in vitro and Franzdiffussion cell. The minimal inhibitory concentration (MIC) and minimum bactericidalconcentration (MBC) of M-NE to Escherichia Coli, Salmonellosen and Shigella dysenteriaewere measured by the double dilution method. The relative bioavailability of M-NE wascalculated by the mequindox concentration in plasma after administering M-NE to the skin ofpiglets. The piglets with white scour were treated by high, medium and low dose of M-NE, bythe results of which the clinical efficacy of M-NE was evaluated.Results:(1) Results of preparation and quality investigation of M-NE. The formula ofM-NE contained30.25%RH40,6.20%cinnamaldehyde,1.24%mequindox and62.31%water. The M-NE was transparent yellow liquid with the structure pattern of O/W. Thedroplets of M-NE were spherical and well distributed with the average particle size of13.9nm and PDI of0.060.(2) Results of stability investigation of M-NE. The Zeta potential of M-NE that had been diluted5times was9.4mV (pH=5.1). The M-NE had fine stability without illumination at normal or low temperature， and its period of validity could be24months.(3)Results of safety evaluation of M-NE. The rats in skin acute toxicity test behaved normallyand no one died，which showed that M-NE had little skin acute toxicity. M-NE had no skinirritation to complete skin, and the average value of irritation of single dosing of M-NE wasless than0.5, which belonged to nonirritant. Multiple dosing of M-NE caused light irritation(0.5~0.7) to the skin in the first5days, and the average value dropped to nonirritant after the5thday.(4) Results of efficacy research of M-NE. The transdermal permeability of M-NE washighly superior to mequindox solution. The accumulation quantity of mequindox of M-NEwas3times more than that of the mequindox solution, and it was not necessary to add azoneas penetration enhancer. The M-NE had very significant anti-bacteria effect compared to themequindox solution, and its MIC to Escherichia Coli, Salmonellosen and Shigella dysenteriaewere4,4and1μg·mL-1, respectively. Its MBC to the three bacteria species were the same asMIC. The bioavailability of M-NE to the piglets was6.94times higher than mequindoxsolution, and the controlled-release effect of M-NE was highly significant. The cure rates topiglets with white scour of M-NE at high and medium dose were both over83%, and theireffective rates were both over95%, which were significantly better than mequindox solutiontransdermal agent, and the medium dose of M-NE was recommended as clinical medicationdose.Conclusion: The M-NE prepared in this research satisfied the requirement ofnanoemulsion formulation and had fine stability, safety and efficacy.