Table 1. The physical properties and permeability characteristic of model drugs.

Compound	Molecular formula	Mw	Water solubility (mg/)a	pK a b	%FAc	P e(10−6 cm/s)d
						C8	C10	C12
Amoxicillin	C16H25N3O8S	419.46	3430	2.6, 7.31, 9.53	93	4.6±0.4	5.3±0.3	5.7±0.4
Atenolol	C14H22N2O3	266.39	1.33×104	9.54	54	3.8±0.4	5.2±0.4	5.9±0.5
Chloroamphenicol	C11H12Cl2N2O5	323.13	2500	4.3	90	8.8±0.2	9.8±0.3	14.6±0.3
Cimetidine	C10H16N6S	252.34	9380	7.23	85	2.6±0.4	2.8±0.3	3.2±0.3
Famotidine	C8H15N7O2S3	337.45	1000	7.24, 11.19	40	2.7±0.3	2.8±0.2	3.2±0.4
Ibuprofen	C13H18O2	206.28	21	4.59	95	13.9±0.5	14.5±0.5	16.7±0.4
Metformin Hydrochloride	C4H11N5·HCl	165.63	Freely soluble	12.4	55	2.4±0.4	2.9±0.3	3.4±0.2
Metoprolol Tartrate	(C15H25NO3)2·C4H6O6	682.82	1.69×104	9.56	95	9.2±0.6	10.3±0.5	11.7±0.5
Norfloxacin	C15H18N3O3F	319.34	1.78×105	6.26, 8.63	35	0.9±0.1	1.0±0.1	1.0±0.1
Ranitidine	C13H24N4O3S·	314.37	24.7	8.2	55	1.2±0.1	1.4±0.1	1.5±0.1

^a Data come from DrugBank database

^b Data collected from Chinese Pharmacopoeia, 2005 edition and references [15,27,38]

^c %FA data obtained from references [16,40]

^d Incubation time is 16h