Rat to Human Equivalent Dose Calculator

Rat to Human Equivalent Dose (HED) Calculator

Based on FDA Body Surface Area (BSA) Normalization Guidelines

Calculation Results

Human Equivalent Dose (HED): mg/kg

Total Suggested Human Dose: mg

*Results are calculated using the standard Km ratio (6/37) for adult humans.*

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How to Convert Rat Dose to Human Equivalent Dose (HED)

In pharmacological research and clinical trial design, converting a dose used in animal studies (like rats) to a safe starting dose for humans is critical. This process is not a simple 1:1 ratio based on weight. Instead, it relies on Body Surface Area (BSA) normalization, which accounts for differences in metabolic rates and physiological processes between species.

The FDA BSA Formula

The standard formula used by the FDA for dose conversion is:

HED (mg/kg) = Animal Dose (mg/kg) × (Animal Km / Human Km)

Key Conversion Constants (Km)

The Km factor represents the ratio of body weight (kg) to surface area (m²). For converting from rats to adult humans, the following constants are typically used:

• Rat Km: 6
• Human Adult (60kg) Km: 37

To find the multiplier, we divide the animal Km by the human Km: 6 ÷ 37 ≈ 0.162. This means the human dose in mg/kg is approximately 16.2% of the rat dose in mg/kg.

Real-World Example

Suppose a study finds that a specific supplement has beneficial effects in rats at a dose of 50 mg/kg. To find the HED for a 70 kg human:

1. Calculate mg/kg: 50 mg/kg × 0.162 = 8.1 mg/kg.
2. Calculate Total Dose: 8.1 mg/kg × 70 kg = 567 mg.

Therefore, the equivalent dose for a 70 kg human would be approximately 567 mg per day.

Disclaimer: This calculator is for educational and informational purposes only. It is intended to assist in understanding the mathematical relationship between species-specific dosages. Always consult with a medical professional or toxicologist before applying animal data to human consumption or clinical applications.

function calculateHED() { var ratDose = document.getElementById('ratDose').value; var humanWeight = document.getElementById('humanWeight').value; var resultsArea = document.getElementById('resultsArea'); if (ratDose === "" || humanWeight === "" || ratDose <= 0 || humanWeight <= 0) { alert("Please enter valid positive numbers for both the Rat Dose and Human Weight."); return; } // Constants var ratKm = 6; var humanKm = 37; // Formula: HED (mg/kg) = Animal Dose * (Animal Km / Human Km) var conversionFactor = ratKm / humanKm; var hedMgKg = ratDose * conversionFactor; // Total Dose: mg/kg * total human kg var totalMg = hedMgKg * humanWeight; // Display Results document.getElementById('hedMgKgResult').innerHTML = hedMgKg.toFixed(3); document.getElementById('totalMgResult').innerHTML = Math.round(totalMg).toLocaleString(); resultsArea.style.display = 'block'; // Smooth scroll to result resultsArea.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }