Section F · Interactive Tool
PepGuide Steady-State Calculator
Select a peptide to auto-load published human PK, then estimate accumulation and the steady-state concentration envelope under a repeated fixed-dose regimen.
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Educational kinetics tool: not medical or dosing advice. Estimates use a simple one-compartment model; investigational and gray-market values carry real uncertainty, and a molecule’s steady state is not the same as the steady state of its biological effect.
Inputs
Semaglutide▾
mg▾
days▾
days▾
mL
Steady-State Output
≈ 4.3 half-lives to 95% SSAccumulation factor (R)iAccumulation factor (R). How much higher the steady-state level is than after a single dose. R = 1 means no buildup; R = 2 means levels roughly double with repeated dosing.
1.98×
Time to 95% steady stateiTime to 95% steady state. How long of continuous dosing until levels plateau near their final value, about 4.3 half-lives. Until then, concentrations are still climbing.
29.7days
Cₛₛ,avgiAverage steady-state concentration (Cₛₛ,avg). The modeled interval mean at plateau. It requires route/formulation-compatible Vd plus F, or apparent Vd/F; unsupported estimates stay disabled.
0.113mg/L
Cₛₛ peak → troughiPeak and trough. The highest level just after a dose and the lowest just before the next one, at steady state. A wide gap means levels swing a lot between doses.
0.16 → 0.08mg/L
Reading the model: Cₛₛ peak assumes instantaneous input: the full dose appears at time zero, then decays. Real subcutaneous peaks arrive later and may be lower. Absolute concentration is shown only with route/formulation-compatible PK; an apparent Vd/F already includes bioavailability, so F is not applied a second time.
kₑiElimination rate constant (kₑ). The fraction of drug cleared per unit time. Derived from the half-life: kₑ = ln(2) / t½. Larger kₑ means faster clearance. = ln(2) / t½ · R = 1 / (1 − e−kₑτ) · t95% = −ln(0.05) / kₑ ·
Cₛₛ,avg = (F · Dose) / (kₑ · Vd · τ), or Dose / (kₑ · [Vd/F] · τ) with apparent Vd/F
Excluded Peptides
Adamax: No published human pharmacokinetic data.
Adipotide (FTPP): A steady-state target isn’t useful: the intended biology is adipose vascular apoptosis, while the risk (renal toxicity) is exposure/safety-driven. No human PK.
AHK-Cu: Topical/local copper tripeptide; systemic human half-life not established.
ARA-290 (cibinetide): Plasma exposure is a few minutes to ~20 min, but the repair signal outlasts plasma; not a meaningful concentration steady-state target.
BPC-157: No validated human PK for oral/SC/IM use; reviews cite <30 min metabolism but nothing route-specific. Gastric stability is not a dosing target.
Cerebrolysin: A mixture of peptide fragments, not a single PK entity, so no single half-life applies.
Dermorphin: Potent opioid peptide; no routine human PK and steady-state framing is unsafe outside controlled settings.
Dihexa: No validated human half-life or route-specific human PK; effect-duration claims are speculative.
Epithalon (Epitalon): Reliable human PK not established; 30–60 min claims are secondary, not route-specific. Longevity claims are pharmacodynamic hypotheses.
FOXO4 / FOXO4-DRI: No reliable human PK; preclinical senolytic concept where steady state is the wrong endpoint.
GHK-Cu: Short plasma persistence reported, but no consistent systemic human PK for topical/injectable use. Local exposure matters more than steady state.
Glutathione (oral/topical): Oral GSH is poorly bioavailable; even IV (included) is only a teaching estimate, not a true steady state.
HGH Fragment 176-191: Reliable human half-life not established. Don’t borrow AOD-9604 or hGH PK values for it.
hMG (menotropin): FSH component ~11–13 h (Menopur label), but follicular/spermatogenic response takes far longer than PK steady state and needs endocrine monitoring.
IGF-1 LR3: Commonly cited 20–30 h, but not from an FDA-approved human label; as a potent growth-factor analog this is not a validated dosing model.
KPV: Human PK not established across oral/topical/nanoparticle/SC; route and formulation dominate exposure.
MOTS-c: Human injection PK not established; metabolic effects are signaling questions, not a guessable steady state.
NAD+: Endogenous coenzyme with rapid extracellular metabolism; intracellular pool dynamics do not map onto a plasma steady-state model.
Pinealon: Reliable human PK not established; bioregulator claims should stay preliminary.
Selank: Reliable human PK not established for intranasal use; anxiolytic/nootropic effects are pharmacodynamic.
Semax: Very short systemic exposure described but reliable human PK is limited; CNS-effect claims are pharmacodynamic, not a stable plasma target.
SS-31 (elamipretide): FORZINITY label gives daily SC PK with minimal accumulation but no simple half-life-based steady-state estimate; follow the label for approved use.
TB-500 / Thymosin Beta-4: Product identity varies (full-length Tβ4 vs LKKTETQ fragment vs vendor product); don’t generalize one PK to every vial. No label-grade human PK.
These were left out because steady-state math requires a real elimination half-life (and, for concentrations, a volume of distribution) measured in humans. Plugging in numbers that don’t exist would produce confident-looking but meaningless output.
Note: For many GH-axis peptides (tesamorelin, sermorelin, GHRPs, CJC-1295) the pharmacological effect, a downstream GH/IGF-1 pulse, long outlasts the peptide’s plasma half-life, so “steady state” of the molecule is not the same as steady state of the effect. Investigational/gray-market values carry real uncertainty. This is an educational kinetics tool, not medical advice.