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    Single intravenous dosing

    When a drug is administered by an intravenous injection, all the drug enters the systemic circulation. It is possible to determine how much drug is necessary to reach a desired serum concentration.

     

     

    For example: for the administration of digoxin to a 70 kg patient. What intravenous loading dose should be given to reach an initial target plasma concentration of 1,5 ng/ml?

    Population parameters of digoxin are: Vd = 7,3 L/kg; (Note Therapeutic plasma level = 0,8-2 ng/ml).

    Hint: besides using formulas, the PK-simulator (see below) with sliders can also be used.

     

    Solution:

    Dose / Vd = Cmax     or     Dose = Cmax · Vd

    Vd = 7,3 L/Kg x 70 Kg = 511 L

    Dose = 1,5 ng/ml x 511 L = 0,766 mg

    See how dosing variations give different concentration-time curves here (module 1 for intravenous dosing).

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    What is the inital plasma concentration (C0) when 10 mg of a drug (Volume of Distribution = 3 L/kg) is administered to a 70 kg patient?

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