To reduce florfenicol (FFC) administration frequency in veterinary use, the drug was currently developed into in situ forming gel. Twelve pigs were randomly divided into two groups (six pigs per group). A single i.m. dose of 40 mg/kg body weight (b.w.) was given to pigs, group one was given FFC in situ forming gel, and group two was given FFC conventional injection. High-performance liquid chromatography (HPLC) was used to determine FFC plasma concentrations. There were significant differences (P < 0.01) between FFC in situ forming gel and conventional injection, in pharmacokinetic parameters MRT (mean retention time) (57.79 ± 2.88) h versus (15.94 ± 1.29) h, AUC (area under the concentration-time curve) (421.54 ± 8.97) μg·h/mL versus (168.16 ± 4.59) μg·h/mL, tmax (time of occurrence of cmax ) (9.00 ± 2.68) h versus (4.33 ± 0.82) h, cmax (maximum plasma concentration) (6.87 ± 0.66) μg/mL versus (12.01 ± 0.66) μg/mL, t1/2λz (terminal elimination half-life) (38.04 ± 2.20) h versus (9.15 ± 2.71) h. The results demonstrated that the in situ forming gel system could shorten dosing interval of FFC and thus achieved less frequent administration during long-term treatment.

Two linear polyethylene fractions (Mη, 11,260 and 100,000) and mixtures of these fractions have been isothermally crystallized from the melt under pressures up to 3000 atm. Characterization of individually crystallized fractions with transmission electron microscopy indicates that pressure can be used to produce a crystallite whose thickness is a measure of the chain length within it. Although the high molecular weight fraction yields spherulites containing individually varying lamellae thicknesses, the maximum thickness of each lamella is a measure of the chain length within it. Both electron micrographs and differential thermal analysis results show that crystallization of homogeneous mixtures of the high and low molecular weight fractions under high pressure results in a distinct fractionation and segregation according to molecular weight.

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