Pharmacodynamic Emax Model Calculator | PharmacyFreak.com

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Pharmacodynamic Emax Model Calculator

Model drug effect using stimulatory, sigmoid, and inhibitory Emax/Imax equations

PharmacyFreak.com · Educational Tool

Model Inputs

Active Formula

E(C) = E0 + (Emax × C) / (EC50 + C)

Conc:

Effect:

µM ↔ mg/L Conversion

Mol. Weight (g/mol)

µM value

Core Parameters

Baseline Effect (E0) iEffect in the absence of drug. The starting point of the E-C curve. %

Max Effect (Emax) iMaximum additional effect above baseline. For inhibitory: maximum possible inhibition. %

EC50 iConcentration producing 50% of Emax. Lower EC50 = more potent drug. ng/mL

Hill Coefficient (γ) iControls steepness of E-C curve. γ=1: hyperbolic. γ>1: sigmoidal. γ=2 doubles steepness.

Single-Point Calculation

Concentration (C) iDrug concentration at which to evaluate the model. ng/mL

💊 Dose → Concentration Helper

Simplified estimate: C₀ = (Dose × F) / Vd — not a full PK model.

Dose (mg)

Vd (L)

F (0–1)

Enter dose, Vd, and F to estimate concentration.

Results

Live

E(C) — Predicted Effect

—

% of Emax Achieved

—

E0 (Baseline)

—

ΔE (Change from Baseline)

—

Detailed Calculation ▶

Enter values to see breakdown.

🔁 Reverse Solver — Find C for Target Effect

Target Effect (E_target) %

Enter a target effect above.

Effect–Concentration Curve

Curve Generator

C min

C max

Points (N)

C (ng/mL)	E(C) (%)

Understanding the Parameters

E0 — Baseline effect without any drug. This anchors the curve.

Emax / Imax — The maximum possible drug effect (or inhibition). Represents the ceiling of drug action.

EC50 / IC50 — Potency parameter. The concentration at which 50% of maximum effect is achieved. Lower = more potent.

Hill coefficient (γ) — Shape parameter. γ = 1 gives a simple hyperbola. γ > 1 creates a steeper sigmoidal curve. γ < 1 flattens it. Clinically, γ values of 1–3 are common.

Note: These are simplified equilibrium models. They don't account for time-dependence, active metabolites, or receptor kinetics.

⚠ Educational tool only. Validate all results with clinical context and pharmacometric modeling standards.

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com