TABLE 2.

Pharmacokinetic parameters for each isoniazid preparation according to the number of “wild-type” high-activity (NAT2*4) and low-activity (NAT2*X) alleles^a

Dose (mg)	No. of NAT2*4 alleles (n)b	AUC/dose (h/liter)	Cmax/dose (1/liter)	tmax (h)	t1/2 (h)	Bioavailability (%)	Vdss (liters)
100, oral	0 (13)	0.091 (0.067-0.132)**	0.021 (0.015-0.037)*	0.50 (0.33-1.00)	3.58 (1.70-10.40)	90.5 (79.2-113.3)
	1 (2)	0.048**	0.017*	1.25	2.20	87.4
		0.048**	0.009*	0.50	6.02	92.8
	2 (3)	0.031 (0.027-0.037)**	0.012 (0.0117-0.015)	0.33	3.82 (2.55-4.75)	78.4 (74.7-89.3)
300, oral	0 (13)	0.107 (0.077-0.154)**	0.026 (0.015-0.039)	0.50 (0.33-2.50)	4.40 (2.44-5.86)	107.2 (91.8-115.9)
	1 (2)	0.066**	0.026	0.50	2.52	118.8
		0.048**	0.015	0.33	6.57	92.0
	2 (3)	0.041 (0.036-0.042)**	0.018 (0.017-0.027)	0.33 (0.33-0.50)	3.39 (2.46-3.93)	100.1 (98.2-105.9)
200, i.v.	0 (13)	0.102 (0.066-0.138)**	0.034 (0.019-0.041)		4.18 (2.08-5.02)		51.8 (30.0-71.1)
	1 (2)	0.055**	0.031		1.96		43.6
		0.051**	0.029		5.32		98.2
	2 (3)	0.040 (0.036-0.042)**	0.026 (0.019-0.029)		4.27 (2.76-4.38)		77.5 (77.1-109)

^aThe parameters were derived directly from the data using the standard noncompartmental approach. AUC, area under the concentration-time curve; C_max, maximal plasma concentration; t_max, time of occurrence of C_max; t_1/2, apparent elimination half-life; V_dss, volume of distribution at steady state; i.v., intravenous. The 300-mg isoniazid dose was administered in combination with 60 mg vitamin B₆. *, P < 0.05; **, P < 0.01 in the Kruskal-Wallis test comparing genotypes. For all other parameters, there was no significant difference. Values are medians (range).

^bFor n = 2, both values are shown.