Plasma protein binding of liquiritin (2 μg mL⁻¹) plus metoprolol in BSA (x̄ ± s, n = 3).

Drug	C total (μg mL−1)	C free (μg mL−1)	Plasma protein binding (%) (with liquiritin)	Plasma protein binding (%) (without liquiritin)
Metoprolol	0.50 ± 0.02	0.37 ± 0.01	26.01 ± 2.37a	28.15 ± 2.02
	1.00 ± 0.03	0.71 ± 0.03	29.19 ± 2.66a	29.67 ± 2.42
	1.99 ± 0.04	1.39 ± 0.03	29.95 ± 1.60a	28.36 ± 1.65

^a p > 0.05, vs. metoprolol without liquiritin.