Interactions

What must not be mixed, and the mechanism that makes it dangerous. Combinations belong here whether the other substance is recreational, prescribed, over the counter or a food: additive respiratory depression when depressants are stacked, serotonin syndrome where two serotonergic drugs meet, hypertensive crisis with an MAOI, QT prolongation from two drugs that each prolong it a little, and the quiet kind — an enzyme inhibitor that does nothing itself while raising the blood level of everything metabolised through it.

This is the default page on every molecule because combination risk is the most consequential thing a reference like this can get right or wrong. Read it as incomplete: no list of pairs is exhaustive, most combinations have never been studied in a person, and an absence of a warning here means nobody has looked rather than that a pair is fine. Prescribed medicines count, and so does timing — some interactions outlast the drug that caused them.