Pharmaceutical Research

, Volume 27, Issue 8, pp 1644–1658 | Cite as

In Situ Artificial Membrane Permeation Assay under Hydrodynamic Control: Permeability-pH Profiles of Warfarin and Verapamil

Research Paper



To investigate the permeation of two ionisable drug molecules, warfarin and verapamil, across artificial membranes. For the first time since the introduction of the parallel artificial membrane permeation assay (PAMPA) in 1998, in situ permeation-time profiles of drug molecules are studied.


The method employs a rotating-diffusion cell where the donor and acceptor compartments are separated by a lipid-impregnated artificial membrane. The permeation of the solute is investigated under well-defined hydrodynamic conditions with control over the unstirred water layer. The flux of the permeating molecule is analysed in situ using UV spectrophotometry.


In situ permeation-time profiles are obtained under hydrodynamic control and used to determine permeability coefficients. An advanced analytical transport model is derived to account for the membrane retention, two-way flux and pH gradient between the two compartments. Moreover, a numerical permeation model was developed to rationalise the time-dependent permeation profiles. The membrane permeability, intrinsic permeability and unstirred water permeability coefficients of two drug molecules are obtained from two independent methods, hydrodynamic extrapolation and pH profiling, and the results are compared.


Both warfarin and verapamil exhibit high permeability values, which is consistent with the high fraction absorbed in human. Our results demonstrate that a considerable lag-time, varying with the solute lipophilicity and stirring rate, exists in membrane permeation and leads to incorrect compound ranking if it is not treated properly. Comparison of the permeability data as a function of pH and stirring rate suggests that some transport of the ionized molecules occurs, most likely via ion-pairing.


hydrodynamic control in situ permeation PAMPA permeability unstirred water layer 



membrane area


hydrodynamic exponent


bio-mimetic PAMPA


time-dependent solute concentration


colorectal adenocarcinoma cell epithelial line


2-(Cyclohexylamino)ethanesulfonic acid


aqueous diffusion coefficient


membrane diffusion coefficient


dioleoyl phosphatidylcholine


dioleoyl phosphatidylcholine PAMPA


double-sink PAMPA


neutral fraction of the solute


membrane thickness


hexadecane PAMPA


immobilised artificial membrane


time-dependent solute flux


distribution coefficient


octanol/water distribution coefficient


Madin-Darby canine kidney epithelial cell line


(not specified) permeability coefficient


intrinsic permeability coefficient


parallel artificial membrane permeation assay


effective (measured) permeability coefficient


membrane permeability coeffcient




unstirred water layer permeability coefficient


polyvinylidene fluoride


fractional membrane retention




unstirred water layer




unstirred water layer thickness


kinematic viscosity





We thank our industrial collaborator, AstraZeneca, and EPSRC for funding and Dr. J. Matthew Wood (AstraZeneca, Alderley Park) for consultation and training in the industrial PAMPA method.

Supplementary material

11095_2010_150_MOESM1_ESM.doc (1.8 mb)
Appendix (DOC 1812 kb)


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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  1. 1.School of ChemistryUniversity of ManchesterManchesterUK
  2. 2.AstraZeneca, MeresideCheshireUK

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