Pharmacology & Dosage
Intermediate

Steady-State Concentration

Average plasma drug concentration when intake and elimination are balanced.

Formula

Css=F×DCL×τC_{ss} = \frac{F \times D}{CL \times \tau}

Variables

C_{ss}Steady-state concentration
FBioavailability (fraction absorbed)
DDose per interval
CLClearance
\tauDosing interval

Example

F=1, D=500 mg, CL=5 L/hr, τ=8 hr → Css = 12.5 mg/L

Did You Know?

Steady state is typically reached after about five half-lives of repeated dosing.

pharmacologysteady stateconcentrationdosing

Share this formula

More in Pharmacology & Dosage

View all

Drug Half-Life

Intermediate

Time for the plasma concentration of a drug to fall to half its initial value.

Loading Dose

Intermediate

Initial higher dose to rapidly achieve the desired plasma concentration.

Maintenance Dose

Intermediate

Recurring dose needed to sustain the steady-state concentration.

Volume of Distribution

Basic

Apparent volume into which a drug distributes — a larger Vd means the drug leaves the bloodstream and enters tissues.

Clearance

Intermediate

Volume of plasma completely cleared of a drug per unit time.

Bioavailability

Intermediate

Fraction of an oral dose that reaches systemic circulation compared with an IV dose.