\[LD=(Ct*Vd)/F\]
Variables
LDloading dose (mg)
Cttarget plasma concentration (mg/L)
Vdvolume of distribution (L)
Fbioavailability
Description
What is this formula?
The Loading Dose (LD) calculates the initial amount of drug required to rapidly achieve a desired target plasma concentration.
When to use it
Use this formula when immediate therapeutic drug levels are needed, particularly for drugs with long half-lives.
Example
Data:
Ct = 10 mg/L
Vd = 40 L
F = 0.8
Formula:
LD = (Ct × Vd) / F
Substitution:
LD = (10 × 40) / 0.8
Result:
LD = 500 mg
Applications
- Antibiotic therapy
- Antiarrhythmic drugs
- Antiepileptic medications
- Therapeutic drug monitoring
- Critical care pharmacotherapy