A
drug interaction is a situation in which a substance (usually another drug) affects the activity of a
drug when both are administered together. This action can be
synergistic (when the drug's effect is increased) or
antagonistic (when the drug's effect is decreased) or a new effect can be produced that neither produces on its own. Typically, interactions between drugs come to mind (drug-drug interaction). However, interactions may also exist between drugs and foods (drug-food interactions), as well as drugs and
medicinal plants or
herbs (
drug-plant interactions). People taking
antidepressant drugs such as
monoamine oxidase inhibitors should not take food containing
tyramine as hypertensive crisis may occur (an example of a drug-food interaction). These interactions may occur out of accidental misuse or due to lack of knowledge about the
active ingredients involved in the relevant substances.