Mixing drugs — why combinations kill more than any single drug

Here is the number most people never hear: most fatal overdoses involve more than one substance. Mixing is not additive — it is multiplicative. Two depressants together can stop your breathing at doses either one would survive alone. A stimulant masks a downer’s warning signs until it is too late. And medicines mixed without a doctor’s oversight — a friend’s prescription, a pill from a stranger, a drink on top of a sleep aid — are the single most common path into an overdose. These 61 plain-language guides explain exactly why each combination is dangerous, what the mix does to your body, the warning signs of trouble, and what to do in the first minutes.