- To determine the effects of albumin (BSA) concentration in perfusion medium on digoxin transfer in isolated perfused human placental cotyledon. Isolated placental cotyledons from 13 normal human placentas were dually perfused after cannulating artery and vein of the chorionic plate and piercing 4 catheters through the corresponding basal plate with M199 medium enriched with BSA and glucose. Flow rates were 12 and 6 ml/min in the maternal and fetal circuits, respectively. Digoxin was added to the maternal reservoir at a final concentration of 5.51 +/- 1.00 ng/ml. BSA in maternal and fetal perfusate was kept at 3 concentrations: 1, 3 and 5 mg/ml (Groups I, II, III). Transplacental passage of digoxin was calculated from repeated fetal and maternal perfusate samples collected over 3 hours in the 3 groups. Digoxin levels were measured by FPIA (TDx, Abbott). There was no transfer of digoxin from the maternal to fetal compartment when the concentration of BSA was 1 mg/ml. Increasing the concentration of BSA led to a substantial increase in the transfer of digoxin to the fetal compartment. Steady state levels of digoxin in the fetal compartment were 0.61 +/- 0.19 ng/ml at 3 mg/ml of BSA. Maternal and fetal serum concentration of BSA affect digoxin transfer in isolated perfused human placentas. Three mg/ml are considered to be the optimal albumin concentration.