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Pharm Question

Discussion in 'Medical Students - MD' started by Pythagoras, Dec 4, 2005.

  1. Pythagoras

    Pythagoras Senior Member
    7+ Year Member

    May 13, 2003
    Likes Received:
    I've been trying to figure this out for a while and i feel like an idiot for not being able to get the right answer, any help would be appreciated.

    A new aminoglycoside antibiotic (5mg/kg) was infused IV over 30 min to a 70kg volunteer. The plasma concentration of the drug was measured at various times after the end of the infusion, as recorded below.

    Time after dosing stopped (hr) Plasma concentration (ug/mL)
    0.0 18.0
    0.5 10.0
    1.0 5.8
    2.0 4.6
    3.0 3.7
    4.0 3.0
    5.0 2.4
    6.0 1.9
    8.0 1.3

    The elimination half life is ~3.5 hrs

    The apparent volume of distribution is approximately?

    The total body clearance is approximately?

    any help would be appreciated. thanks
  2. tupac_don

    tupac_don Senior Member
    5+ Year Member

    May 16, 2004
    Likes Received:

    This is what you do, find ke (ke=ln(5.8/1.3)/t8 - t1 Use values for 1hr after infusion and 8 hrs after end of infusion.

    When you have ke you can double check t1/2=.693/k

    Cmax=5.8/e-ke * t1 (0.5), then Cmin=Cmax (e-(ke*T-t (use 7.5))

    For Vd= Dose/Cmax - Cmin

    CrCl= Vd * ke * 1000/60

    Good luck.

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