Loading Dose (LD) and Maintenance Dose (MD)

Feature

Loading Dose

Maintenance Dose

Purpose

To quickly achieve therapeutic
drug levels

To maintain drug levels within
the therapeutic range

Timing

Given at the beginning of
therapy

Given throughout treatment
at regular intervals

Amount

Usually higher than the
maintenance dose

Lower and consistent

Used For

• Drugs with long half-life 

or delayed onset

• During emergency

All long-term therapies

Formula

(intra venous)

LD (i/v) = (Target conc. × Vd)

MD (i/v) = (Target concentration × CL)

Dependence

Depends on
Volume of Distribution (Vd)

[PYQ: NEET PG 2024]

Depends on Clearance (CL)

Risk

Higher risk of toxicity if overdosed

Safer, but may lead to accumulation
if not adjusted