GLP-1 Incretin Pharmacokinetic Plotter
Simulate multi-dose superposition, blood serum decay curves, and steady-state equilibrium for Semaglutide, Tirzepatide, Retatrutide, and custom peptide regimens.
Protocol Configuration
1 CompoundPredicted Active Circulating Mass (mg)
Understanding Incretin Pharmacokinetics: Half-Life, Accumulation, and Steady-State
Long-acting GLP-1 receptor agonists (such as Semaglutide) and dual/triple polyagonists (such as Tirzepatide and Retatrutide) are engineered with lipophilic fatty acid diacid tails that non-covalently associate with endogenous human serum albumin. This reversible bioconjugation shields the peptides from renal clearance and neutral endopeptidase degradation, extending elimination half-lives to 5 to 7 days.
| Compound | Proprietary Brand | Receptor Profile | Elimination Half-Life (t½) | Bioavailability (F) | Peak Window (Tmax) |
|---|---|---|---|---|---|
| Tirzepatide | Mounjaro, Zepbound | Dual GIP / GLP-1 | 5.0 Days (120 hrs) | 80% (Subcutaneous) | 24–48 Hours |
| Semaglutide | Ozempic, Wegovy | GLP-1 Mono-agonist | 7.0 Days (168 hrs) | 89% (Subcutaneous) | 24–36 Hours |
| Retatrutide | LY3437943 (Phase 3) | Triple GIP / GLP-1 / GCG | 6.0 Days (144 hrs) | 80% (Subcutaneous) | 24–48 Hours |
| Cagrilintide | CagriSema Component | Long-Acting Amylin | 7.5 Days (180 hrs) | 85% (Subcutaneous) | 24–48 Hours |
| Survodutide | BI 456906 (Phase 3) | Dual Glucagon / GLP-1 | 6.0 Days (144 hrs) | 80% (Subcutaneous) | 24–36 Hours |
| Liraglutide | Victoza, Saxenda | Daily GLP-1 Mono-agonist | 0.54 Days (13 hrs) | 55% (Subcutaneous) | 8–12 Hours |
| Oral Semaglutide | Rybelsus (SNAC Form) | Oral GLP-1 Mono-agonist | 7.0 Days (168 hrs) | 1.0% (Transcellular) | 1–2 Hours |
Why Does Medication "Stack" in the System?
When a drug is administered at an interval shorter than 4 to 5 half-lives, a substantial fraction of the previous dose remains in circulation when the next dose is introduced. For instance, with Tirzepatide's 5-day half-life, approximately 38% of the preceding weekly injection is still active at Day 7. With each consecutive dose, drug levels stack in an upward stair-step trajectory until the rate of drug elimination equals the rate of drug entry:
STEADY-STATE ACCUMULATION EQUATION
R = 1 / (1 - e^(-ke · τ)) = 1 / (1 - 2^(-τ / t½))
Where τ is the injection frequency (e.g., 7 days) and ke is the elimination rate constant (ln 2 / t½).
At weekly intervals (τ = 7), Tirzepatide achieves an accumulation factor R ≈ 1.61×, meaning steady-state peak levels are approximately 61% higher than after the very first injection. This explains why clinical protocols mandate 4-week titration intervals: it takes 4 to 5 half-lives (~25 to 35 days) for circulating levels to plateau at steady state before escalating dose mass.
The Science of Split Dosing (3.5-Day Interval vs. 7-Day Interval)
A frequent challenge in preclinical and clinical incretin therapy is the Peak-to-Trough Variance. After a large once-weekly injection, serum concentration reaches a sharp maximum (Cmax) between 24 and 48 hours, coinciding with nausea and gastrointestinal adverse events. By Day 6 and 7, concentrations fall toward the trough (Cmin), frequently accompanied by waning appetite suppression.
By partitioning the identical weekly mass into two equal doses every 3.5 days (e.g., Sunday morning and Wednesday evening):
- The peak (Cmax) is blunted by 35% to 45%, markedly attenuating receptor saturation surges.
- The trough (Cmin) is elevated by 20% to 30%, preserving consistent, unbroken receptor engagement.
- Total cumulative exposure (Area Under the Curve, AUC) remains mathematically identical.