What Are PK Related Terminologies
What Is PK (Pharmacokinetic) Related Terminologies?
Here are main PK (Pharmacokinetic) related terminologies as shown in this FDA picture:
Drug Concentration - Drug Concentration is usally measured as the amount of the drug in a unit of blood volumn.
Cmax (maximum concentration) - Cmax is the highest concentration of drug in the blood that is measured after the drug is taken.
Tmax - Tmax is the time to reach the Cmax after the drug is taken.
Cmin (minimum concentration) - Cmin is the lowest concentration of drug in the blood that is measured after the drug is taken.
If the drug is taken as a single dose, the Cmin should be closed to zero.
If the drug is taken as a repeated dose, the Cmin should be the drug concentration right before the next dose.
Cmin is also called "Trough".
AUC (Area Under the Curve) - AUC is the area under the curve of the drug concentration over time. AUC represents the overall amount of drug in the bloodstream after a dose.
Since drug concentrations are measured with some time intervals, not continuously, The AUC is usually calculated with an approximation that simulates the actual the drug concentration curve.
tÂ½ (Half Life) - tÂ½ is the amount of time it takes for the drug concentration in the blood to decline by half. The half-life is among the most important PK measurements for how often a drug has to be dosed (once-a-day or twice-a-day, etc).
SS (Steady State) - SS means that a person has been on a drug for enough time (usually one to two weeks) so that the drug concentration is not building up in the bloodstream anymore.
MTC (Minimum Toxic Concentration) - MTC is the lowest concentration of drug in the blood that toxicity usually occurs.
MEC (Minimum Effective Concentration) - MEC is the lowest concentration of drug in the blood that is required for drug effect.
TW (Therapeutic Window) - TW is the range of drug concentration between the MEC (Minimum Effective Concentration) and the MTC (Minimum Toxic Concentration).
TI (Therapeutic Index) - TI refers to several indices that are used for measuring a drug's safety. Higher TI means a safer drug. Lower TI means a dangerous drug. Two examples of TI are:
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