A liposome preparation that is amenable to receptor-mediated endocytosis has been developed to enhance the oral bioavailability of poorly absorbable peptidomimetic drugs by use of folic acid as the mediator of liposomal uptake.
A high-performance liquid chromatographic method with ultraviolet (UV) detection was developed for measuring cefotaxime in rat and human plasma. The method used direct injection of the plasma supernatant after deproteinization with 70% perchloric acid. Degradation of cefotaxime in acidic medium was retarded by adding phosphate buffer before centrifuging the sample. The mobile phase was 0.05 M aqueous ammonium acetate-acetonitrile-tetrahydrofuran (87:11:2, v/v) adjusted to pH 5.5. Analysis was run at a flow-rate of 1.0 ml/min, and a detection wavelength of 254 nm was used. The method has a quantification limit of 0.20 microgram/ml. The within- and between-day coefficients of variation and accuracy values were less than 8% and +/-3%, respectively, while the recovery values were greater than 87% over the concentration range tested (0.20-50 microgram/ml). The speed, sensitivity, specificity and reproducibility of this method make it particularly suitable for the routine determination of cefotaxime in human plasma. Moreover, only a relatively small sample plasma volume (100 microliter) is required, allowing this method to be applied to samples taken from neonates.
A liposome system was evaluated for oral delivery of a poorly bioavailable hydrophilic drug. The system was prepared from proliposome, which consisted of negatively charged phosphatidylcholine, whereas cefotaxime was chosen as the model drug. An in vivo study was carried out on nine rats according to a three-way crossover design to compare the oral bioavailability of cefotaxime from the liposomal formulation with that of an aqueous drug solution and a physical mixture of cefotaxime with blank liposomes. The results indicated that the extent of bioavailability of cefotaxime was increased approximately 2.7 and 2.3 times compared with that of the aqueous solution and the physical mixture, respectively. In a separate study, simultaneous determination of cefotaxime in intestinal lymph (collected from the mesenteric lymph duct) and in plasma (collected from the tail vein) revealed that its concentration was consistently higher in the lymph than in the plasma when administered via the liposomal formulation, whereas the reverse was observed with the aqueous solution. Thus, the results indicated that the liposomes system has the potential of increasing the oral bioavailability of poorly bioavailable hydrophilic drugs and also promote their lymphatic transport in the intestinal lymph.