Overlay up to four dosing protocols and watch how half-life, interval, and cycle length interact. Useful for questions like “how long until a weekly peptide reaches steady state?” or “does switching from BPC-157 daily to twice-weekly change the peak-to-trough spread?”
Tirzepatide
2.5 × 12 every 168h · half-life 120.0h
~95% of steady state after 21.6 days · SS mean 1.288
BPC-157
0.25 × 28 every 24h · half-life 0.5h
~95% of steady state after 0.1 days · SS mean 0.004
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The chart uses a one-compartment pharmacokinetic model. For each administered dose, the concentration over time follows a rise-then-fall envelope:
C(t) = D · (1 − e^(−k·Δt)) · e^(−k·Δt), where k = ln(2) / t½
Concentration at any time is the sum across every dose administered before that time. The first factor is the absorption rise; the second is the elimination decay. With regular dosing, the curve approaches a plateau — steady state — where each dose's contribution is balanced by the previous doses' decay.
The horizontal dashed line on the chart is the steady-state mean:
C_ss_mean = D / (2·k·τ)
where τ is the dosing interval. A compound reaches ~95% of steady state after about 4.3 half-lives of regular dosing — the classical rule of thumb.
Two compounds with the same weekly dose can produce very different steady-state concentrations if their half-lives differ by 10×. A peptide with a 30-minute half-life dosed once weekly is just a series of pulses that don't talk to each other; a peptide with a 168-hour half-life dosed once weekly smooths into a near-flat plateau after a month or so.
The same math explains why short-half-life peptides are typically dosed 2–4× per day (to keep trough concentrations above threshold) while long-half-life GLP-1s are weekly (because the trough is already high enough after the first four or five doses).