Plasma Concentration Plotter

How the Plasma Concentration Model Works

This tool uses a one-compartment first-order elimination model — the standard framework for subcutaneous peptide pharmacokinetics. For each dose at time t₀, remaining concentration follows: C(t) = Dose × e^(−0.693 × t / t½). For repeated dosing, concentrations from all previous doses are summed at each time point.

Steady-State Accumulation

With weekly GLP-1 agents like tirzepatide (t½ = 5 days) or semaglutide (t½ = 7 days), plasma levels accumulate over 4–5 weeks before reaching steady state. The trough level at steady state is approximately Dose / (e^(λτ) − 1) where λ = ln(2)/t½ and τ is the dosing interval. This tool visualizes exactly when your levels plateau and what your peak-to-trough ratio will be.

Why This Matters Clinically

Understanding steady-state timing helps explain why GLP-1 side effects (nausea, satiety) often peak in weeks 3–5 as levels accumulate — not week 1. For repair peptides with short half-lives (BPC-157 at 4 hours), daily dosing produces sawtooth peaks rather than accumulation, which informs split-dosing decisions.

Model Limitations

This is a simplified single-compartment model assuming uniform bioavailability and linear kinetics. Actual plasma levels vary based on injection site, body composition, binding proteins, and metabolic differences. Volume of distribution is normalized. Use for educational and planning purposes only.