Studies On Pharmacokinetics Of Long-term Cefquinome Microspheres In Pigs

Cefquinome is the first dedicated fourth-generation cephalosporin for animals. It has wide antimicrobial spectrum, strong antibacterial activity, fast absorption and elimination rate,and won’t cause renal toxicity. Now the only dosage form listed is injection generally. CEF is a time dependent drug, with short half-life, so maintaining effective blood drug concentration in animals need increasing the number of treatment. Microspheres is a new drug formulations, which parcel or adsorb into the ball with some biodegradable polymer materials as the carrier. Microspheres transfer the drugs with the specific release rate and dose to the biological parts. The study attempts to make microspheres with gelatin as the carrier, in order to prolong effect-time and decrease the times of clinical medication and improve the sterilization effect of CEF.The first step of microspheres is preparing blank microspheres. Through single factor experiment, choose four main influence factors of microsphere preparation process, including stirring velocity, W/O, concentration of gelatin and concentration of the emulsifier (Span-80). According to the L9(34) orthogonal experiment,we determine the best combination of various factors, and identify the primary and secondary impact of the four factors on the preparation of microspheres:gelatin concentration, stirring velocity, W/O, Span-80concentration.In preparing CEF-GMS, we set the different CEF/gelatin on the basis of optimum blank microspheres preparation process, choose the best CEF/gelatin through these indicators:appearance, size, drug loadings and the encapsulation efficiency of microspheres. The best preparation technology for CEF-GMS:Weighing gelatin0.3g, PEG60000.03g, CEF O.lg, put them into water (3mL), the water temperature is50℃. Put liquid paraffin50mL into round bottom flask, add Span-802mL into the oil phase, puts water phase2.5mL into oil phase with a syringe under the rotate speed1000r/min, emulsifying15min, then turn into the ice bath. When the temperature is1-5℃stable, put glutaraldehyde3mL into the system, add20mL isopropyl alcohol to the system after90min crosslinking. Dehydrate30min, Wash off the oil phase and excessive glutaraldehyde by isopropyl alcohol, ethyl ether, petroleum ether. transfer the microspheres to dryer in Circulating water vacuum pump for24h, store drying CEF-GMS in ampoules.CEF-GMS prepared by the best technology was spherical with microporous structure at microsphere surface, and the mean diameter was (9.15±0.59)μm, drug loading was (37.89±1.34)mg/g, encapsulation efficiency was81.73%±2.10%.In pharmacokinetic study of pigs, in accordance with4.0mg/kg bw for intramuscular injection, Collecting pig plasma at different time, settling protein by10%perchloric acid, centrifugal precipitation, taking supernatant for HPLC analysis. The correlation coefficient of curve is more than0.9999. The average recovery is more than80%from plasma. The intra-day and inter-day coefficient of variations are less than5%、10%. The drug concentration-time curve in the plasma of CEF and CEF-GMS are all fitted two-compartment open models. The curves equation of concentration-time in plasma are C=9.5331e-0.6644t.1314e-0.1495t-11.6645e-2.7525t and C=3.1838e-0.1642t+0.7556e-0.0154t-3.93disposition half-lives(T1/2a) are (1.04±0.27)h and (4.22±0.37) h, respectively. The absorption half-lives(T1/2ka) are (0.25±0.05)h and (1.07±0.14)h, respectively; The elimination half-lives(T1/2p) are (4.64±1.22)h and (45.12±5.60)h, respectively; The maximum concentration(Cmax) are (6.22±1.94)μg/mL and (2.11±0.61)μg/mL, respectively; The peak time(Tp) are (0.74±0.11)h and (3.20±0.98)h, respectively; The areas under the concentration-time curve(AUC) are (24.38±3.65) μg-h/mL and (62.51±7.35)μg-h/mL, respectively; The clearance rate(CLs) are (0.24±0.07) L/(kg-h) and (0.06±0.02)L/(kg-h); The distribution volumes(V/Fc) are (0.51±0.18)(mg/kg)/(μg/mL) and (0.76±0.35)(mg/kg)/(μg/mL), respectively. The results revealed that CEF-GMS has good delayed-release effect compared with active pharmaceutical ingredients.