Pharmacokinetic tool
Half-Life & Dosing Interval Calculator
Simulate the steady-state concentration curve for any research peptide, with a clear view of the accumulation factor that drives interval selection.
Inputs
Half-life: 168 h
Time to steady state: ~35 days
Accumulation factor: ×2.00
Avg steady-state level: 1000 mcg
Steady-state concentration curve
Single-compartment first-order elimination model. Each spike represents an administration; the decay between is exponential with the peptide's half-life.
The arithmetic
The simulator uses a single-compartment first-order elimination model. The elimination rate constant k is derived from the peptide's half-life: k = ln(2) ÷ t½. The accumulation factor at a given interval τ is 1 ÷ (1 − e−kτ) — the multiplier applied to a single-dose concentration to obtain the steady-state average. Practical steady state is generally reached after five half-lives.
Why interval matters
A peptide with a 168-hour half-life such as Semaglutide reaches steady state in roughly 35 days, and its accumulation factor on a weekly schedule is around 2.0 — meaning the average steady-state concentration is double the single-dose peak. By contrast, a peptide with a 30-minute half-life such as Tesamorelinachieves no measurable accumulation; each dose acts independently.
Supporting research
- Knudsen LB et al., Mechanism of GLP-1 receptor agonist pharmacokinetics, Diabetes Obes Metab, 2010.
- Falutz J et al., Long-term safety and effects of tesamorelin, Clin Endocrinol, 2010.
- Rowland M, Tozer TN, Clinical Pharmacokinetics and Pharmacodynamics (4th ed), Lippincott, 2011.