> 50% of prescription drugs are 3A4 substrates—plenty of fish!
0% of individuals are 3A4 ultrarapid metabolizers. Less than 1% are poor metabolizers.
Conclusion: 3A4 is the workhorse of CYP metabolism, accounting for 30% of hepatic CYP activity and 70% of CYP activity in the gut. Since > 50% of drugs are 3A4 substrates, think twice before prescribing strong 3A4 inhibitors or inducers.