7Steady State Concentration IV Infusion until reaching Css
8Steady State Concentration (Css) Theoretical SS is only reached after an infinite infusion timeRate of elimination = kel Cp
9Steady 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 …….
10Steady State Concentration (Css) In clinical practice, the SS is considered to be reached after five half-lives
11Increasing 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.
12Loading Dose plus IV Infusion DL with IV infusion at the same timeLoading doseIV infusionDL + IV infusion
13Loading Dose plus IV Infusion DL is used to reach SS rapidly
14Reaching SS Immediately Let , DL = CssVd But, CssVd = R / kelTherefore, if a DL = R / kel is given SS will be reached immediatelybut
15Reaching SS Immediately IV DL equal to R /kel is given, followed by IV infusion at a rate R