Increase of plasma nonesterified fatty acid concentration and decrease of albumin binding affinity after intravenous injection of glycocholate-lecithin mixed micelles.

Lipophilic drugs intended for intravenous use can be solubilized by mixed-micellar systems containing glycoholic acid and lecithin (MM). Our present studies determined the influence of such MM preparations on albumin binding of monoacetyldiaminodiphenyl sulfone (MADDS), a deputy ligand for bilirubin. After intravenous administration of MMs to healthy male and female adult volunteers, concentration-time profiles of bile acid and nonesterified (NEFA) and esterified fatty acids were obtained as well. In vitro experiments with blood from adults and from neonatal cords indicated a modest reduction in reserve albumin for binding of MADDS after addition of MMs, resulting from glycocholic acid in the micellar preparation. After injection of MM preparations with up to 530 mg glycocholic acid, a rapid decrease of the reserve albumin was observed. The effect was more pronounced in men than in women and resulted in different areas under the time curve for the decrease (p = 0.049). At their maximum (3 to 10 minutes after MM doses) the decreases averaged (+/- SD) 68% +/- 14% in men and 45% +/- 8.5% in women. Low reserve albumin concentrations were maintained over 20 minutes despite rapidly declining bile acid concentrations. Injection of MM caused a drastic increase of NEFA in the serum samples with a more pronounced effect in men (average +/- SD increase: 473% +/- 93%) than in women (148% +/- 91%) (p = 0.01). The changes in NEFA concentrations ran reciprocal to the changes of reserve albumin for binding MADDS. In all subjects the increase in NEFA was accompanied by a decrease in reserve albumin for palmitate. Fatty acid binding to albumin was well restored within 1 hour. Thus, before drugs incorporated in MM can be prescribed to neonates who are at risk for having kernicterus, the impact of intravenous MM on bilirubin binding and NEFA levels must be investigated in that patient population.