Blood-brain barrier permeation: molecular parameters governing passive diffusion

J Membr Biol. 1998 Oct 1;165(3):201-11. doi: 10.1007/s002329900434.


53 compounds with clinically established ability to cross or not to cross the blood-brain barrier by passive diffusion were characterized by means of surface activity measurements in terms of three parameters, i.e., the air-water partition coefficient, Kaw, the critical micelle concentration, CMCD, and the cross-sectional area, AD. A three-dimensional plot in which the surface area, AD, is plotted as a function of K-1aw and CMCD shows essentially three groups of compounds: (i) very hydrophobic compounds with large air-water partition coefficients and large cross-sectional areas, AD > 80 A2 which do not cross the blood-brain barrier, (ii) compounds with lower air-water partition coefficients and an average cross-sectional area, AD congruent with 50 A2 which easily cross the blood-brain barrier, and (iii) hydrophilic compounds with low air-water partition coefficients (AD < 50 A2) which cross the blood-brain barrier only if applied at high concentrations. It was shown that the lipid membrane-water partition coefficient, Klw, measured previously, can be correlated with the air-water partition coefficient if the additional work against the internal lateral bilayer pressure, pibi = 34 +/- 4 mN/m is taken into account. The partitioning into anisotropic lipid membranes decreases exponentially with increasing cross-sectional areas, AD, according to Klw = const. Kaw exp(-ADpibi/kT) where kT is the thermal energy. The cross-sectional area of the molecule oriented at a hydrophilic-hydrophobic interface is thus the main determinant for membrane permeation provided the molecule is surface active and has a pKa > 4 for acids and a pKa < 10 for bases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism
  • Air
  • Amiodarone / pharmacokinetics
  • Animals
  • Blood-Brain Barrier*
  • Brain / metabolism*
  • Butyrophenones / pharmacokinetics
  • Diffusion
  • Domperidone / pharmacokinetics
  • Histamine H1 Antagonists / pharmacokinetics
  • Humans
  • Kinetics
  • Loperamide / pharmacokinetics
  • Micelles
  • Models, Biological
  • Piperidines / pharmacokinetics
  • Surface Properties
  • Thermodynamics
  • Water


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Butyrophenones
  • Histamine H1 Antagonists
  • Micelles
  • Piperidines
  • Water
  • Domperidone
  • Loperamide
  • carebastine
  • Amiodarone
  • ebastine