In medicine and pharmacology, a<unk>  or<unk>  concentration <unk>  is the concentration reached by a drug immediately before the next dose is administered, often used in therapeutic drug monitoring. The name comes from the idea that on a graph of concentration versus time, the line forms a U-shaped<unk>  at the lowest region, before a new dose sends it higher again. The usual criterion is concentration in the blood serum, although in some instances local concentration within tissues is relevant. It is pharmacokinetically normal that over time, the drug molecules are being metabolized or cleared by the body, so the concentration of drug that remains available is dropping. In a medicine that is administered periodically, the<unk>  should be measured just before the administration of the next dose in order to avoid overdosing. A<unk>  is contrasted with a "peak<unk> " (Cmax), which is the highest<unk>  of the medicine in the body, and the "average<unk> ", which is the mean<unk>  over time. It is widely used in clinical trials for newer medicines to investigate therapeutic effectiveness and safety.<unk>  is slightly different from Cmin, the minimum concentration during the time interval between administration of two doses.
Trough level
Fractional kill
Peak-to-trough ratio
Minimum bactericidal concentration
Median lethal dose
Toxic equivalency factor
Equivalent dose
Time-activity curve