Cytochrome P450
Cytochrome P450 (CYP) enzymes are a family of membrane-bound proteins that carry out much of the body's metabolism of medicines; inhibiting or inducing them is a major mechanism behind drug interactions.
What it means in practice
In humans, almost 80% of oxidative metabolism and approximately 50% of the overall elimination of common clinical drugs can be attributed to CYPs from families 1 to 3, according to a 2021 review [2]. A 2024 review calls them the major catalysts involved in drug metabolism [3].
The names group enzymes into families and subfamilies; the CYP1A subfamily, for example, includes CYP1A1 and CYP1A2 [2]. The drug-metabolizing set includes CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4, and CYP3A4 and CYP2D6 contribute to over 50% of CYP-related drug metabolism [2]. The CYP3A subfamily is responsible for the metabolism of over 30% of drugs used today and is the most abundant CYP in the human body [2].
A substance can bind a CYP as an inhibitor or an inducer, and CYP induction or inhibition is a major mechanism underlying drug-drug interactions [2]. A 2022 systematic review of herbs and medicines on the Indian market observed both activation and inhibition of CYP450 enzymes, and because many medicines are CYP substrates, inhibitors or inducers, an interacting herb could change how a co-administered drug behaves [1]. Activity also differs between people: genetic polymorphisms, epigenetic changes and environmental factors may explain interethnic and interindividual differences in how well drugs work [2].
Why it matters when reading nootropics research
When a monograph cites a CYP finding, check whether it came from cells, enzymes or animals, or from people. A laboratory result shows a possible mechanism. NootropicsWork labels it as mechanism and does not count in vitro CYP data alone toward a safety flag.
Even for medicines, a 2024 review lists predicting drug-drug interactions among the practical problems that continue in drug development [3], so a laboratory signal is a reason to look for human data rather than a verdict. On this site, mentions of CYP3A4, CYP2C9 and CYP1A2 link to this entry.
References
- Sharma AK, Kapoor VK, Kaur G. Herb-drug interactions: a mechanistic approach. Drug Chem Toxicol. 2022.
- Zhao M, Ma J, Li M, et al. Cytochrome P450 Enzymes and Drug Metabolism in Humans. Int J Mol Sci. 2021.
- Guengerich FP. Roles of Individual Human Cytochrome P450 Enzymes in Drug Metabolism. Pharmacol Rev. 2024.