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Flockhart Table™

Indiana University School of Medicine's Cytochrome P450 Drug Interaction Table

The Drug Interaction Flockhart Table™ is designed as a teaching and reference tool for health care providers and researchers interested in drug interactions that are mediated by cytochrome P450 enzymes.

The effective, intelligent management of many problems related to drug interactions in clinical prescribing can be helped by an understanding of how drugs are metabolized. Specifically, if a prescriber is aware of the dominant cytochrome P450 isoform involved in a drug's metabolism, it is possible to anticipate, from the inhibitor and inducer lists for that enzyme, which drugs might cause significant interactions. The Flockhart Table™ is focused on clinically relevant interactions, and is updated at least twice yearly.

The table contains eight columns, one for each of the P450 isoform groups. In each column you will find:

  • Substrates: drugs that are metabolized as substrates by the enzyme
  • Inhibitors: drugs that prevent the enzyme from metabolizing the substrates
  • Inducers: drugs that increase the enzyme's ability to metabolize the substrates

A drug appears in a column if there is published evidence that it is metabolized, at least in part, via that isoform. It does not necessarily follow that the isoform is the principal metabolic pathway in vivo, or that alterations in the rate of the metabolic reaction catalyzed by that isoform will have large effects on the pharmacokinetics of the drug.

The Flockhart Table™ only catalogs drug-drug interactions that are mediated by CYPs. Drug-drug interactions caused via other enzymes (e.g., UGTs) are not included in this table. In addition, some of the drugs listed could be substrates of uptake and efflux drug transporters. However, drug-drug interactions caused by inhibition or induction of drug transporters are not included in the table.

View the drug interaction table

View the drug interaction table

The information presented in the Flockhart Table™ is intended as general health information and as an educational tool. It is not intended as medical advice.

View the table


If you use this site in your work, please acknowledge it by citing the following reference:

Flockhart DA, Thacker, D., McDonald, C., Desta, Z. The Flockhart Cytochrome P450 Drug-Drug Interaction Table. Division of Clinical Pharmacology, Indiana University School of Medicine (Updated 2021). Accessed [date].

Contact Us

Questions or feedback about the Drug Interaction Flockhart Table™? Contact Christine McDonald, Division Administrator and Director of Finance for the Division of Clinical Pharmacology.

Email Christine McDonald