acetaminophen antipyrine ^^hydrochlorothiazide


log Kp (octanol-water)

Figure 7.39 Intrinsic permeabilities (iso-pH data analysis) versus octanol-water partition coefficients.

curve is extended to higher pH values. Thus less evidence of membrane-limited transport is visible in the physiological pH range when the soy lecithin system is used. For this reason, correction for the UWL effect is all the more important when devising oral absorption prediction models, which reflect the pH gradient found in the small intestine.

TABLE 7.16 Permeability (10"6 cm/s units) and Retention in 20% wt/vol Soy Lecithin, at Iso-pH 5.0, 6.5, 7.4 with Sink in Acceptor Wells


pH 5.G


pH 6.5


pH 7.4



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