Table 1.

Intravenous and Oral Alfentanil Pharmacokinetic Parameters.

	Control	Acute Ritonavir/Indinavir	Steady-state Ritonavir/Indinavir
IV alfentanil
Cmax, ng/ml	85 ± 21		72 ± 16
Cmax/dose, ng · ml−1 · mg−1	84 ± 23		107± 21 *
AUC0-∞, ng · h−1 · ml−1	51 ± 16		458± 229 *
AUC0-∞/dose, ng · h−1 · ml−1 · mg−1	50 ± 12		680 ± 323 *
AUC0-∞/dose ratio, ritonavir-indinavir/control			12.7 (8.5–18.9)
CLIV, ml · kg−1 · min−1	5.30 ± 1.47		0.44 ± 0.19 *
Elimination t1/2, h	1.0 ± 0.2		10.8 ± 6.1 *
EH	0.35 ± 0.10		0.03 ± 0.01 *
Oral alfentanil
Cmax, ng/ml	25 ± 8	60 ± 21 *	60 ± 21 *
Cmax/dose, ng · ml−1 · mg−1	9 ± 2	35 ± 5 *	38 ± 14 *
AUC0-∞, ng · h−1 · ml−1	52 ± 25	1130 ± 420 *	834 ± 358 *†
AUC0-∞/dose, ng · h · ml−1 · mg−1	18 ± 7	657 ± 133 *	538 ± 253*
AUC0-∞/dose ratio, ritonavir-indinavir/control		40 (24–66)	30 (18–52)
CL/F, ml · kg−1 · min−1	16.8 ± 7.5	0.4 ± 0.1 *	0.5 ± 0.2 *
Elimination t1/2, h	1.0 ± 0.1	12.2 ± 3.0 *	13.3 ± 6.2 *
Foral	0.34 ± 0.08		0.81 ± 0.08 a
EG	0.48 ± 0.10		0.18 ± 0.10 a

AUC = area under the plasma concentration-time curve; C_max = peak plasma concentration; CL_IV = systemic clearance of IV alfentanil; CL/F = apparent oral clearance of alfentanil; E_H = hepatic extraction; E_G = intestinal extraction; F_oral = bioavailability.

^*Significantly different from control (P < 0.05).

^†Significantly different from acute ritonavir-indinavir (P < 0.05).

Subjects received 15 and 10 μg/kg intravenous (IV) alfentanil and 43 and 23 μg/kg oral alfentanil at the control and ritonavir/indinavir sessions, respectively. Peak plasma concentration (C_max) and area under the concentration-time curve (AUC) are shown normalized to dose. All other variables are not dose adjusted. Results are the arithmetic mean ± SD (n=12), except the AUC_0-∞/dose ratio (ritonavir-indinavir/control), which is the geometric mean (90% confidence interval).