A good antimicrobial follows the rule of selective toxicity: harm the microbe, spare the patient. In practice that means dosing into a narrow band — high enough to work, low enough to be safe. Slide the dose and watch it cross from too low, into the window, and up to toxic. Then switch drugs to see how the window widens or narrows.
Slide the dose
MEC = minimum effective concentration; MTC = minimum toxic concentration. The green band between them is the therapeutic window. Dose is on a relative 0–100 scale, since real serum levels differ for every drug.
The therapeutic windowpick a drug, then slide the dose