When use of black market heroin laced with fentanyl started killing drug users, news reports blamed fentanyl's higher "potency." A recent headline warns that sufentanil is even "stronger" than fentanyl. But neither potency nor strength makes one drug more dangerous than another.
In fact, potency just refers to numbers. It means that .05 mg of one drug may have the same effect as 500 mg of another drug. We call the maximum clinical effect of a drug efficacy, roughly synonymous with strength. A small syringe of heroin can contain a lethal dose, but drinking a quart of (much less potent) vodka might kill you just as dead.
The absence of regulated labeling informing the user of what the product contains and how much contributes to harm from drugs purchased on the black market.
If we want to minimize harm from drug use, including overdose, rather than attention-grabbing headlines misusing sensationalistic terms, we need policies that assure that those who use the drugs know what and how much they contain and what risks go along with that use.