What does MEC stand for?

• A. Maximum effective concentration
• B. Minimum effective concentration
• C. Mean effective concentration
• D. Minimum toxic concentration

Answer: (B)

Minimum effective concentration is the lowest concentration in plasma or at the site of action that produces the desired therapeutic effect. This threshold helps define the level above which the drug is expected to work, and dosing aims to keep blood levels above this point to maintain efficacy. The therapeutic window is the range between the MEC and the minimum toxic concentration (MTC); staying above MEC ensures effectiveness, while staying below MTC minimizes toxicity. The other options don’t fit: “maximum effective concentration” isn’t a standard term for efficacy, “mean effective concentration” isn’t used in pharmacology, and “minimum toxic concentration” refers to the onset of toxicity, not the desired effect.