FIGURE 1.

The therapeutic reference range of a drug within which a drug response without major toxic side effects can be expected. (A) Above the maximum therapeutic concentration (MTC), there is an increased risk of toxicity, and below the minimum effective concentration (MEC), there is likely to be a lack of response. The peak concentration C _max is reached a certain time after the dose has been administered, and the trough level C ₀ is when the next dose should be administered. A representative AUC for the first 12 h after dosing (AUC_0–12h) is indicated. (B) Interpatient variability: An example of an interference with drug absorption, leading to a low C _max and low C ₀ (orange curve) compared with the ideal case (blue curve). An example of an interference with drug elimination (red curve), which is commonly caused by either kidney dysfunction or liver dysfunction. C _max is normal, and C ₀ is high after the first dose, and both do gradually increase with subsequent doses