How does melatonin interact with medications or food?

Tell your doctor about all the medicines, supplements, or vitamins that you take (prescription or over-the-counter). Use of melatonin may make antidepressants, blood pressure medicines, beta-blockers, blood-thinning medicines, steroids, and immunosuppressant drugs less effective. NSAIDs (non-steroidal anti-inflammatory drugs, like Motrin and Advil), caffeine, tobacco, and alcohol all may lower the body's levels of melatonin.
Some drug interactions with melatonin are positive. Some antipsychotic medications worked better when paired with melatonin. The same is true for benzodiazepines and interleukin-2 (a cancer drug). Also, the combination of melatonin and tamoxifen, another cancer drug, proved beneficial in preliminary research.