TABLE 5

Kinetic characteristics of nifedipine biotransformation in vitro by HLMs, rCYP3A4, and rCYP3A5, and IC50 values with ketoconazole by HLMs, rCYP3A4, and rCYP3A5 Results are expressed as mean ± S.E.



Oxidized Nifedipine

HLMs (n = 4)
rCYP3A4
rCYP3A5
V max a 20.4 ± 8.3 9.9 10
Km (μ M) 25.3 ± 9 4.5 25.8
Vmax/Kmb 767 ± 77 2200 388
IC50 for ketoconazole (μ M)
0.15 ± 0.1
0.024
0.19
  • a Units are nmol/min/mg protein for HLMs and nmol/min/pmol P450 for rCYP3A4 and rCYP3A5.

  • b For clearance (Vmax/Km ratio), units are μl/min/mg protein for HLMs and μl/min/pmol P450 for rCYP3A4 and rCYP3A5.