Interaction
An interaction is a change in how a supplement or medicine acts when it is combined with another, either in how much reaches the body or in the combined effect, and it can raise the risk of adverse events.
What it means in practice
Reviews sort interactions by how they happen. A 2012 systematic review of documented interactions between herbs or dietary supplements and medicines found 882 interactions with a described mechanism and severity [1]. Of these, 42.3% were due to altered pharmacokinetics, a change in how much of a medicine reaches and stays in the body [1]. The review described 240 of them as major [1]. Other interactions act on the combined effect, which a 2022 systematic review of herbs and medicines on the Indian market describes as synergistic or antagonistic [2].
The 2012 review counted 1,491 unique supplement-drug pairs, involving 213 herb and supplement entities and 509 medications, drawn from 85 primary publications, six books and two websites [1]. Products containing St. John's Wort, magnesium, calcium, iron and ginkgo had the most documented interactions, and warfarin, insulin, aspirin, digoxin and ticlopidine had the most reported interactions with supplements [1]. The interactions concentrated in a relatively small subset of commonly used medicines and supplements [1].
Another route runs through drug-metabolizing enzymes. The 2022 review 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 [2].
Why it matters when reading nootropics research
An interaction listed on a compound page can rest on very different evidence: a human pharmacokinetic study, a trial, a case report or a laboratory experiment. NootropicsWork counts a human interaction study, or a reference that names a medicine with a narrow safe range, toward a compound's safety flag. Laboratory data alone, or a single case report alone, do not count.
A compound page that lists no interaction with a medicine means its sources reported none, not that the combination was tested and found free of problems. The 2012 review's authors wrote that their summary would help health-care professionals communicate documented interactions to patients [1]. Each monograph lists the interactions its sources report and refers readers who take any of the named medicines to a doctor or pharmacist.
References
- Tsai HH, Lin HW, Simon Pickard A, et al. Evaluation of documented drug interactions and contraindications associated with herbs and dietary supplements: a systematic literature review. Int J Clin Pract. 2012.
- Sharma AK, Kapoor VK, Kaur G. Herb-drug interactions: a mechanistic approach. Drug Chem Toxicol. 2022.