U01.21.005 Maintenance Dose (MD)

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Learning Objective:
Understand and apply the formula for calculating the maintenance dose (MD) required to maintain a target steady-state plasma concentration during repeated or continuous drug administration.

Formula:

$text{Maintenance dose} = frac{C_p times CL times tau}{F}$

Explanation:

$C_p$ = Desired plasma concentration at steady state
$CL$ = Clearance (rate at which the drug is eliminated from the body)
$tau$ = Dosing interval (time between doses)
$F$ = Bioavailability (fraction of the administered dose that reaches systemic circulation; for IV drugs, $F = 1$ )

The formula ensures that the rate of drug administration equals the rate of drug elimination at steady state, maintaining a consistent therapeutic plasma level.

Example:

Given:
$C_p = 10 text{ mg/L}$
$CL = 5 text{ L/h}$
$tau = 12 text{ h}$
$F = 0.8$