Pharmacokinetic Studies On Norfloxacin Lactate In Mandarinfish(Siniperca Chuatsi)

Norfloxacin lactate belongs to the third generation of quinolones, and it had been approved for production and use. It was applied in the treatment of aquatic animal bacterial diseases because of its better water solubility, wider antimicrobial spectrum and weaker cumulative advantages. September 2015, the Ministry of Agriculture announced that prohibiting the use of norfloxacin various salts, esters and their preparations in food animals since December 31, 2015. In order to understand the law of absorption and elimination and analyze the security risk of the drug in the aquatic animals, it is necessary to study the pharmacokinetics of the drug in the aquatic animal.In this study, mandarinfish as the experimental object and HPLC fluorescence detection method was used to compare several extraction effect of extraction solvent on norfloxacin lactate in mandarinfish plasma. The results showed that norfloxacin lactate could not be extracted by acetonitrile in plasma and could not be extracted by ethyl acetate in muscle. Acetonitrile and dichloromethane have certain extraction effect to norfloxacin lactate but the recovery rate was low. 0.025 mol / L phosphate- acetonitrile(87:13) mobile phase has a better recovery effect for norfloxacin lactate, and the maximum recovery rate can up to 92.41% in plasma and 57.378% in the muscle. The phosphoric acid – acetonitrile with different volume ratio was used to extract norfloxacin lactate which exists in mandarinfish plasma and muscle. It showed that the recovery rate was highest of norfloxacin lactate in muscle when ratio of phosphoric acid and acetonitrile was 1: 3. Practice has proved that the reduction of nitrogen blow enrichment step still to achieve a good recovery effect. Final extraction method was determined: Using 1 times volume of the 0.025mol/L phosphate- acetonitrile(87:13) mobile phase as extractant to extract of the drug in plasma, with 10 times the size of 0.025 mol / L phosphate- acetonitrile(1:3) mixed solution for drug on the extraction of muscle. 5 times the volume of acetonitrile saturated hexane was used to remove the fat, and the filtrate was detected on machine after filtering by 0.45μm membrane twice. The method has the advantages of simple operation, rapid extraction, high recovery efficiency for norfloxacin lactate in aquatic product residue detection and other related research.In order to compare and analyze plasma protein binding properties of norfloxacin lactate with tilapia and mandarinfish(siniperca chuatsi), the equilibrium dialysis method and HPLC method were used to determine the drug concentration in vitro. The results indicate that plasma protein binding rate of norfloxacin lactate with two kinds of fish can reach steady state within 48 h, and the plasma protein binding rate would be reduced significantly(P<0.05) as the increase of drug concentration. When the drug concentration in the range of 1~40μg/m L, protein binding rate of norfloxacin lactate with tilapia plasma changes from 0 to 42.987% while it changes from 2.748% to 33.992% with mandarinfish plasma. The rate of protein binding of norfloxacin lactate with mandarinfish was higher at low drug concentration, on the contrary, the rate of the same drug with tilapia was higher at high drug concentration. This study showed that plasma protein binding rate was linear no better tilapia or mandarinfish. There was a moderate protein binding rate of norfloxacin lactate in aquaculture and it has a good drug efficacy.In order to study the metabolism and elimination rule of norfloxacin lactate in mandarinfish(siniperca chuatsi),HPLC method was used to analyze status of drug concentration in plasma and other organizations after a single oral dose of 20 mg·kg-1 body weight at(28±2)℃. The results showed: The peaking time(Tmax) of the drug in plasma, muscle, liver and kidney were 4.333, 6, 3 and 5 h, and the corresponding maximal drug concentration(Cmax) were 3.625, 2.39, 33.089 and 19.375 mg·L-1, respectively. Among them, the drug concentration which absorbed by liver was highest, followed by kidney, plasma and muscle. The elimination half-life(t1/2 z) of norfloxacin lactate in plasma, muscle, liver and kidney were 42.589, 131.652, 16.830 and 30.558 h. Norfloxacin lactate eliminate fastest in liver and slowest in muscle. According to the maximum residue limit(MRL) of 50 μg·kg-1 in muscle, the withdrawal time should not be less than 24 d under this experiment condition.