IN-VITRO MICRODIALYSIS OF HYDROPHILIC AND LIPOPHILIC COMPOUNDS

The feasibility of microdialysis to study both hydrophilic and lipophi lic compounds was investigated. In vitro microdialysis was performed w ith glucose, sodium fusidate, betamethasone dipropionate and calcipotr iol. For all the tested drugs, recovery was dependent on the dialysed compound, the perfusion rate, the length of the membrane, the temperat ure and the stirring rate in the surrounding medium. Recovery was inde pendent of concentration for glucose, betamethasone dipropionate and c alcipotriol, but was dependent on the concentration of sodium fusidate . Loss (delivery) of betamethasone dipropionate was independent of con centration, whereas loss of sodium fusidate was not. The more lipophil ic the compound, the lower the recovery; 74.6%, 41.0%, 36.4% and 31.1% for glucose, sodium fusidate, betamethasone dipropionate and calcipot riol, respectively. A difference in recovery and loss was found for so dium fusidate, betamethasone dipropionate and calcipotriol, whereas gl ucose had the same recovery and loss. Tn vitro calibration was perform ed with glucose and sodium fusidate. The estimated glucose concentrati on was equal to the true concentration in the surrounding medium. A mo dification of the point of no-net-flux method was necessary to estimat e the true concentration of sodium fusidate. Special tubing was needed for the highly lipophilic compounds betamethasone dipropionate and ca lcipotriol. It may be more critical and problematic to use microdialys is for lipophilic compound and the method might be limited to the stud y for hydrophilic compounds in vivo. (C) 1997 Elsevier Science B.V.