DS-PAMPA

Avdeef, A., Tsinman, O. PAM PA -a drug absorption in vitro model 13. Chemical selectivity due to membrane hydrogen bonding in comho comparisons of HDM-, DOPC-, and DS-PAMPA models. Eur. J. Pharm. Set. 2006, 28, 43-50. 

Composition of the PAM PA membrane varies from a purely organic solvent membrane to a purely phospholipid membrane. At the first international conference of PAM PA in 2002 (www.pampa2002.com/), it was agreed that these variations would be notated as initials or a short adjective at the head of PAMPA (e.g., BM-PAMPA for biomimetic PAMPA). The original PAMPA (Egg-PAMPA) [47], hexadecane membrane PAMPA (HDM-PAMPA) [48], BM-PAMPA [49], double sink PAMPA (DS-PAMPA) and blood-brain barrier PAMPA (BBB-PAMPA) [51] are reviewed elsewhere [3]. 

Falten et al. recently reported that phospholipid membrane vesicles can be con-stmcted on a filter scaffold without any organic solvent [57-60]. In this system, the phospholipid vesicle occupies the filter pores to form a permeation barrier. This is more relevant to the cellular membrane than PAMPA membranes with organic solvent. The membrane can be stored up to two weeks without significant change and is stable at pH 2-8. The Fa% predictability was compared with BM-PAMPA, DS-PAMPA, Caco-2 and immobilized liposome chromatography, resulting in promising predictability. 

Chen et al. reduced the volume of organic solvent (hexadecane) down to 1 j,L per well (usually 4—5 j,L/well) [63]. Phospholipid/hexane solution was applied on both side of the thin hexadecane membrane (40 p,g phospholipid). After the evaporation of hexane, phospholipid/hexadecane/phospholipid tri-layer was formed (according to the original article). With the 2% phospholipid/dodecane membrane (4 p,L/ well) and DS-PAMPA, permeability of some compounds such as caffeine and antipyrine were underestimated, whereas tri-layer PAMPA gave an appropriate estimate. 

Also in the PAMPAmodel, alternatives to BSAhave been explored to improve the biorelevance of the model. To overcome the adsorption and/or absence of sink conditions, different additives that do not require an additional step of sample preparation as compared with the addition of albumin, have been proposed. Recently, the use of Double-Sink PAMPA (DS-PAMPA) was proposed as biorelevant alternative to the classic PAMPA methodology (Avdeef, 2003). In DS-PAMPA, a non-specific binding agent (lipophilic sink) was included in the receiver compartment to create sink conditions. 

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