Loading Dose Calculator
Calculate the loading dose required to rapidly achieve target drug concentration based on volume of distribution and bioavailability.
Patient & Drug Parameters
mg/L (or mcg/mL)
Desired plasma concentration
%
100% for IV, varies for oral (e.g., 80-90% for many drugs)
Fraction of drug that is active (e.g., 0.8 for phenytoin sodium)
Loading Dose
490.0 mg
7.00 mg/kg
💊Total Loading Dose
490.0 mg
⚖️Per kg Dose
7.00 mg/kg
📊Total Vd
49.0 L
🎯Patient Weight
70.0 kg
Formula
Loading Dose = (Cp × Vd) / (F × S)
Where Cp = target concentration, Vd = volume of distribution, F = bioavailability, S = salt factor
Clinical Note
Loading doses should be given with caution. Consider patient factors such as organ function, age, and drug interactions. Consult drug references for specific recommendations.
Common Drug Parameters
| Drug | Vd (L/kg) | Bioavailability | Salt Factor |
|---|---|---|---|
| Digoxin | 5-7 | 70-80% | 1.0 |
| Phenytoin | 0.6-0.7 | 90% | 0.92 (sodium) |
| Theophylline | 0.5 | 96% | 1.0 |
| Vancomycin | 0.4-1.0 | 100% (IV) | 1.0 |
| Aminoglycosides | 0.25-0.3 | 100% (IV) | 1.0 |