Trough Concentration

Trough concentration (Cmin or Ctrough) is the lowest plasma level a compound reaches between doses — typically just before the next scheduled dose. It is an important pharmacokinetic parameter because it sets the floor of receptor occupancy: if trough drops too low, the receptor may completely unbind between doses and the pulsatile profile may produce inferior outcomes compared to steady-state coverage.

Trough is governed by half-life and dosing interval. For semaglutide (t½ ~7 days, weekly dosing), trough is roughly 50% of Cmax — a stable, well-buffered profile. For ipamorelin (t½ ~2 hours, daily dosing), trough is essentially zero by 12 hours — by design, since pulsatile GH release benefits from the receptor being un-occupied between pulses.

Stack design often involves co-managing the troughs of two compounds: pairing a long-half-life GHRH analog with a short-half-life GHRP, for instance, allows the GHRH side to provide steady tone while the GHRP delivers pulses on top.