Trough Concentration (Cmin)
Also known as: Cmin
Trough concentration (Cmin) is the lowest drug concentration in the blood, occurring just before the next scheduled dose. It is relevant for multi-dose research protocols to assess whether a compound maintains meaningful exposure between doses.
Overview
Cmin represents the nadir of drug concentration during a multiple-dosing regimen, typically measured just before the next dose is administered. It is the complement of Cmax in characterizing the oscillation of drug concentration over time. If Cmin falls below the threshold needed for biological activity, there are periods within each dosing interval where the compound has no effect — which may or may not be desirable depending on the research goal. For peptides with very short half-lives, the trough may reach near zero before the next dose (more suitable for pulsatile effects). For peptides with long half-lives, concentrations remain relatively stable between doses with minimal peak-to-trough fluctuation. Optimizing dosing frequency requires understanding both Cmax and Cmin in relation to the compound's therapeutic or research window.
Frequently asked questions
When is the trough concentration measured?+
Trough is measured at the end of a dosing interval, just before the next dose — the lowest point concentration reaches during regular dosing.
What happens if trough concentration falls below the effective level?+
If Cmin falls below the threshold for biological activity, there are gaps in the dosing interval where the compound is pharmacologically inactive. More frequent dosing (or a longer-acting formulation) can eliminate this gap.
Why does Cmin matter more for some peptides than others?+
For peptides where sustained receptor occupancy is needed (e.g., continuous GLP-1 receptor activation for glucose control), maintaining Cmin above the effective threshold is critical. For pulsatile effects (GH release), having concentration drop to near-zero between doses may actually be desirable.