7 Steady State Concentration IV Infusion until reaching Css
8 Steady State Concentration (Css) Theoretical SS is only reached after an infinite infusion timeRate of elimination = kel Cp
9 Steady State Concentration (Css) Rate of Infusion = Rate of Elimination The infusion rate (R) is fixed while therate of elimination steadily increases The time to reach SS is directlyproportional to the half-life After one half-life, the Cp is 50% of the CSS, after 2 half-lives, Cp is 75% of the Css …….
10 Steady State Concentration (Css) In clinical practice, the SS is considered to be reached after five half-lives
11 Increasing the Infusion Rate If a drug is given at a more rapid infusion rate, a higher SS drug concentration is obtained but the time to reach SS is the same.
12 Loading Dose plus IV Infusion DL with IV infusion at the same timeLoading doseIV infusionDL + IV infusion
13 Loading Dose plus IV Infusion DL is used to reach SS rapidly
14 Reaching SS Immediately Let , DL = CssVd But, CssVd = R / kelTherefore, if a DL = R / kel is given SS will be reached immediatelybut
15 Reaching SS Immediately IV DL equal to R /kel is given, followed by IV infusion at a rate R