Cyclosporin solution preparation

Cyclosporine D, ascomycin, and desmethoxyrapamycin were used as internal standards. A stock solution containing 200 /tg/niL cyclosporine D, 20 /tg/mL ascomycin, and 20 /ig/mL desmethoxyrapamycin was prepared in methanol and diluted 1 1000 with methanol/zinc sulfate (50 g/L) aqueous solution (4 1 v/v) before use. 

Sample The standards are created with a plasma originally possessing no cyclosporin. Six different solutions are prepared by adding the necessary quantities of cyclosporin A to each in order to create solutions of 50 ng/ml, 100 ng/ml, 200 ng/ml, 400 ng/ml, 800 ng/ml, and 1000 ng/ml. 1 ml from each of these solutions is subjected to the same extraction sequence following the addition of 250 ng of cyclosporin D to each, as above. 

In aqueous alcoholic solutions, it very readily solubilizes essential oils. Aqueous solutions of hydrophobic drugs (e.g. miconazole, hexetidine, clotrimazole, benzocaine) can also be prepared with Cremophor EL. Cremophor EL has also been used as a solubilizing agent for drugs like cyclosporin A, paclitaxel, and cisplatin. Cremophor LLP is manufactured by purifying Cremophor EL and is therefore suitable for parenteral applications, e.g. Taxol preparations. In oral formulations, the taste of polyoxyl 35 castor oil (Cremophor EL) can be masked by a banana flavor. 

Chen X, Young TJ, Sarkari M, Williams RO, Johnston KP. Preparation of cyclosporine A nanoparticles by evaporation precipitation into aqueous solution. Int J Pharm 2002 242 3-14. 

In a similar fashion, it has been possible to isolate different conformations of the immunosuppressive drug, cyclosporin A. By preparing anhydrous THF solutions of CsA, with and without 0.4 M LiCl, it was possible to restrict the peptide ring system conformation in CsA to trans and cis conformers. Addition of these conformers separately to the assay buffer enabled the dissociation constants of both the cis and trans amide bond conformers in CsA for inhibition of PPIase to be determined. The trans conformer (2337t) is very active the cis conformer (23.37c) is not, and these plus other data were used to show that CsA adopts a conformation in water that is very close to the enzyme-bound CsA conformation. Subsequently, Wenger and coworkers at Sandoz (now Novartis) showed by NMR experiments that a 3-substituted CsA derivative, e.g. (23.38) (Fig. 23.8) adopts a conformation in water that is essentially identical... 

Primary stock cyclosporine D solution, 1 mg/mL (Toronto Research, North York, Canada). Prepare working internal standard solution by diluting stock solution 4x in methanol, to a concentration of250 pg/mL. The solution is stable for 1 year at -20°C. 

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