Partition behaviour of acids and bases in a phosphatidylcholine liposome–buffer equilibrium dialysis system
1997; Elsevier BV; Volume: 5; Issue: 4 Linguagem: Inglês
10.1016/s0928-0987(97)00278-9
ISSN1879-0720
AutoresCornelia Ottiger, Heidi Wunderli‐Allenspach,
Tópico(s)Surfactants and Colloidal Systems
ResumoApparent partition coefficients (D) of (RS)-[3H]propranolol, 14C-lidocaine, 14C-diazepam, 14C-warfarin, 14C-salicylic acid and 14C-cyclosporine A were determined in a phosphatidylcholine (PhC) liposome–buffer system with equilibrium dialysis (37°C, pH 2 to 11). The resulting pH-dependent partition diagrams represent a superposition of Henderson–Hasselbalch equations for the pKa of drug and PhC. True partition coefficients were calculated for the neutral (Pn) as well as for the ionized (Pi) molecules. For all drugs Pn was higher than Pi. A decrease in D was found at pH values where the phosphate group of PhC was protonated (pH≤2). With extruded liposomes D values were lower than with detergent (cholate) dialysis liposomes, which indicates that the residual cholate (1 molecule per 700 PhC molecules) has an influence on the partition behaviour.
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