Drug Interactions Flockhart Table ™

This site is dedicated to the memory of a pioneer in clinical pharmacology and pharmacogenetics and the creator of this site/page, Dr. David A. Flockhart, MD, PhD

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Substrates

Substrates: drugs metabolized by the enzyme.

Color-Coded System: indicates the strength of evidence from literature evaluating the drug as a substrate for specific enzyme.

red Strong Evidence: the enzyme is majorly responsible for drug metabolism.
orange Moderate Evidence: the enzyme plays a significant but not exclusive role in drug metabolism or the supporting literature is not extensive.
green Weak Evidence: the enzyme plays minor role in drug metabolism or the available literature is limited.
In-Vitro Evidence: evidence is based solely on in vitro studies.
TBD: the strength of evidence is under review.

1A2
 
2B6
 
2C8
 
2C9
 
2C19
 
2D6
 
2E1
 
3A4/5
 

Inhibitors

Inhibitors compete with other drugs for a particular enzyme thus affecting the optimal level of metabolism of the substrate drug which in many cases affect the individual's response to that particular medication, e.g. making it ineffective.

red A Strong inhibitor is one that causes a ≥ 5-fold increase in the plasma AUC values or more than 80% decrease in clearance.
orange A Moderate inhibitor is one that causes a 2-fold to < 5-fold increase in the plasma AUC values or 50-80% decrease in clearance.
green A Weak inhibitor is one that causes a ≥ 1.25-fold but < 2-fold increase in the plasma AUC values or 20-50% decrease in clearance.
In-Vitro Only In-Vitro Only evidence only.
TBD Inhibitor strength level is under review.

1A2
 
2B6
 
2C8
 
2C9
 
2C19
 
2D6
 
2E1
 
3A4/5
 

Inducers

Inducers increase the amount of enzyme thus increase the rate of matabolism of a substrate drug which in many cases affects the individuals response to a particular medication, for example, making it ineffective.

red A Strong inducer causes an ≥80% reduction in drub (substrate) exposure (UC)
orange A Moderate inducer causes a 50% to < 80% reduction in drug (substrate) exposure (AUC)
green A Weak inducer causes < 50% reduction in drug (substrate) exposure (AUC)
In-Vitro Only In-Vitro Only evidence only.
TBD Inducer strength level is under review.

1A2
 
2B6
 
2C8
 
2C9
 
2C19
 
2D6 2E1
 
3A4/5