Characterization of pirenzepine interaction with cytochrome P-450

Abstract

1. Pirenzepine interacts with the haem iron of cytochrome P-450 from rat- and pig-liver microsomes, to give absorption spectra with max. at 424–429 nm, and min. at 391–399 nm. Binding to cytochrome P-450 was not detected with human-liver microsomes

2. Inhibition of 7-ethoxycoumarin dealkylation by pirenzepine using rat-liver microsomes gave values of I₅₀ = 5mM and K_is=0.53mM.

3. E.p.r. spectra showed that pirenzepine probably interacts with the haem iron through the pirenzepine N-4¹ tertiary amine group.