Figure 5.

Propranolol acts as an MBI of CYP2D6 in human liver microsomes in vitro. In (a), pooled human liver microsomes (0.1 mg·ml⁻¹) were preincubated with propranolol (0–30 μM) for 5 min before dextromethorphan (5 μM) was added. The difference in dextrorphan (DOR) formation between propranolol preincubation with and without NADPH, before dextromethorphan was added, suggests that propranolol acts as an MBI of CYP2D6 in liver microsomes from humans. In (b), propranolol (0–10 μM) inhibition of dextrorphan formation velocity by pooled human liver microsomes (0.1 mg*ml̂ ‐1) was preincubation time and dose‐dependent. In (c), the rate of inactivation of CYP2D6 (K_obs) by each propranolol concentration was plotted to determine k_inactivation and K_I