TABLE 5

Predictions of F_G and Q_Gut using the Q_Gut model from in vitro clearance and permeability data for 25 drugs

Data are predicted values ± S.D.

Substrate	F_G		Q_Gut Estimated
Substrate	Predicted^{^a}	Observed	Q_Gut Estimated
			l/h
Alfentanil	0.82 ± 0.06	0.60	16.6
Alprazolam	0.99 ± 0.01	0.94	16.4
Atorvastatin	0.90 ± 0.04	0.24	12.7
Buspirone	0.68 ± 0.04	0.21	16.4
Cisapride	0.65 ± 0.06	0.55	16.6
Cyclosporine	0.82 ± 0.07^{^b}	0.44	8.6^{^b}
Felodipine	0.20 ± 0.07	0.45	14.5
Indinavir	0.25 ± 0.07	0.93	5.7^{^c}
Lovastatin	0.10 ± 0.04	0.07	15.4
Methadone	0.97 ± 0.01	0.78	16.2
Midazolam	0.54 ± 0.14	0.51	16.6
Nifedipine	0.66 ± 0.03	0.74	16.3
Nisoldipine	0.08 ± 0.03	0.11	16.3
Quinidine	0.99 ± 0.001	0.90	13.9^{^c}
Repaglinide	0.84 ± 0.05	0.89	16.3
Rifabutin	0.87 ± 0.03	0.21	14.3^{^c}
Saquinavir	0.01 ± 0.003	0.18^{^d}	2.4^{^c}
Sildenafil	0.78 ± 0.02	0.54	16.4
Simvastatin	0.06 ± 0.02	0.14	13.2
Tacrolimus	0.34 ± 0.16	0.14	15.1
Terfenadine	0.11 ± 0.02	0.40	11.9
Trazodone	0.91 ± 0.03	0.83	16.3
Triazolam	0.95 ± 0.04	0.75	16.5
Verapamil	0.67 ± 0.07^{^b}	0.65	15.2^{^b}
Zolpidem	0.98 ± 0.01	0.79	16.6

↵a F_G predictions based on the Q_Gut model (eq. 2) using Caco-2 P_app (A-B) data.
↵b Estimates based on available human P_eff data: cyclosporine 1.65 ± 0.53 μm/s and verapamil 6.8 ± 2.9 μm/s (Lennernäs, 2007).
↵c Indinavir, quinidine, rifabutin, and saquinavir Q_Gut values were 13.8, 16.4, 15.9, and 13.5 l/h, respectively, if no additional contribution of P-gp was assumed (passive permeability only).
↵d F_G data were determined from saquinavir (Invirase); no data were available for saquinavir (Fortovase).