Drug-drug interactions can lead to changes in systemic exposure (e.g., maximum concentration (Cmax), area under the concentration time curve (AUC), average steady state concentration (Cpss)) potentially resulting in adverse reactions (higher drug exposure) or loss of efficacy (lower drug exposure).
Cytochrome P-450 (CYP) enzymes are responsible for the metabolism of many drugs, and transporter systems allow for movement of many drugs across cell membranes. Thus, these enzymes and systems are often implicated in drug-drug interactions because of their effect on a drug’s pharmacokinetics (e.g., drug exposure).
Table 1 provides examples of drugs that interact with CYP enzymes and transporter systems. Table 1 also includes five other substances that interact with CYP enzymes and transporter systems (i.e., St. John’s wort (a dietary supplement), curcumin (a supplement), diosmin (a supplement), tobacco (smoking) and grapefruit juice (a food)). These examples were evaluated and compiled by FDA as an optional resource for healthcare professionals to consult when reviewing information in the DRUG INTERACTIONS section of the approved U.S. Prescribing Information (PI) in clinical practice. Table 2 provides definitions of substrates, inhibitors, and inducers for CYP-based metabolism and Table 3 provides definitions of inhibitors and substrates for drug transporter systems.
The field of metabolic and transporter pharmacology is rapidly evolving, thus the examples in Table 1 are a guide and not considered a comprehensive list of all possible drugs and other substances (e.g., foods, including dietary supplements) that fit these categories. This website contains examples of drugs with CYP enzyme-based and transporter-based interactions but does not include drugs with other mechanisms leading to drug interactions (such as certain interactions affecting drug absorption (e.g., chelating agents, resin-based binders, and drugs that change gut pH), interactions affecting drug plasma protein binding, or pharmacodynamic interactions).
This website contains examples of drugs with CYP enzyme-based and transporter-based interactions but does not include drugs with other mechanisms leading to drug interactions (such as certain interactions affecting drug absorption (e.g., chelating agents, resin-based binders, and drugs that change gut pH), interactions affecting drug plasma protein binding, or pharmacodynamic interactions)
To refine your search for interacting examples of drugs* in CYP-based metabolic- and transporter system-based drug interaction classes, use the filters (in the box below) and/or the search box (located below the filters and above the table of examples).
When using the search box, include the name of the drug substance rather than the name of the drug product or the proprietary name. For example, search for “atorvastatin” instead of “atorvastatin calcium tablets” or “LIPITOR.” The search ignores the following symbols: ., (, ), ‘, -, and /. Thus, when searching for “St. John’s wort,” you will obtain the correct results by typing “St. John’s wort” or “St. John s wort”, but not St. Johns wort”. If you are not sure of the spelling of the drug name, use Browse by Drug Name on the Drugs@FDA home page to find drug names in alphabetical order.
The filters and search box operate using an “and” function. This means the use of two or more filters or the combination of filters with the search box returns results that meet both criteria. For example, if you are searching for strong 2C19 inhibitors (use the CYP strong inhibitor filter and select “2C19” in the drop-down menu) and weak CYP 2B6 inhibitors (use the CYP weak inhibitor filter and select “2B6” in the drop-down menu) the results will:
Thus, if you are searching for strong 2C19 inhibitors OR weak CYP 2B6 inhibitors, conduct your search for each separately.
* Although this website focuses on examples of drugs in CYP-based metabolic- and transporter system-based drug interaction classes, St. John’s wort (a dietary supplement), curcumin (a supplement), diosmin (a supplement), smoking tobacco, and grapefruit juice (a food) are also included in this listing .
Use filters in this box or use the search box (“Search”) that is directly below to refine the results.
CYP strong inhibitor
CYP moderate inhibitor
CYP weak inhibitor
CYP strong inducer
CYP moderator inducer
CYP weak inducer
CYP sensitive substrate
CYP moderate sensitive substrate