Double-sink PAMPA

TABLE 7.22 In Vitro Double-Sink PAMPA Models for GIT and BBB Targets... 

Avdeef A, Artursson P, Neuhoff S, Lazorova L, Grasjo J, Tavelin S (2005) Caco-2 permeability of weakly basic drugs predicted with the double-sink PAMPA pA /l ux method. Eur J Pharm Sci 24 333-349. 

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]. 

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. 

These automated assays can be used for high-throughput ADME screening in early drug discovery. The double-sink PAMPA permeability assay mimics in vivo conditions by the use of a chemical sink in the acceptor wells and pH gradient in the donor wells. The use of the pION gut-box integrated on the deck has shortened the PAMPA assay incubation time to 30 minutes. The permeability coefficient and rank order correlate well with data obtained using the in vitro Caco-2 assay and in vivo permeability properties measured in rat intestinal perfusions. 

Suen Y, Tsinman K, Zhu Z, Threadgill G. Automation of a double-sink PAMPA permeability assay on the Biomek EX Laboratory Automation Workstation. Pharm Discov 2005a, 1 June xx. 

Recently, the double-sink PAMPA assay was introduced to circumvent this problem and to further improve the predictiveness of the method for estimating absorption. The double-sink method involves dosing the test compound into the donor compartment at pH 5... 

Avdeee, A. Artursson, P. Neuhoff, S. Lazorova, L. Grasio, j. Taveun, S. Caco-2 permeabiUty of weakly basic drugs predicted with the double-sink PAMPA pKafflux) method. Eur. J. Pharm. Sci. 2005, 24, 333-349. 

In the BBB-PAMPA lipid formulation illustrated in Fig. 3.4, the diff values, defined as the difference log Pq-log Pi, range from 2.9 (morphine) to 4.2 (warfarin), somewhat similar to the values observed in the octanol-water system. However, it is premature to propose a pdiffi-A approximation, given the limited amount of data reported. With other lipid formulations, larger differences are usually observed. In Double-Sink PAM PA, and especially in hexadecane-PAMPA, transport of ionized drugs has not been reported [84]. 

Figure 7.62 Correlation between human jejunal permeabilities [vs. PAMPA (double-sink)] and soy lecithin models under gradient pH conditions.

Figure 7.67 Human intestinal absorption compared to (a) pION s double-sink sum-P, PAMPA GIT model and (b) human jejunal permeabilities [56],...

In conclusion, the double-sink su m-P, PAMPA in vitro GIT assay seems to predict human absorption as well as in vivo human permeability measurements (see Figs. 7.66a,b) and in vitro Caco-2 permeability measurements (see Figs. 7.60 and 7.63), but at a lower cost and higher speed. 

The lengthy permeability chapter (Chapter 7) recounts the study of many different artificial membrane formulations, comparing transport results of each to human jejunal permeabilities. A very promising in vitro screening system was described the double-sink sum-Pe PAMPA GIT model. It is most applicable to molecules that are classified as soluble in the BCS scheme. 

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