PK of Digoxin

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PK of Digoxin
2013-04-13 17:58:46
Dr Cheung

PT II exam III
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  1. therapeutic plasma concentrations for CHF
    0.5 - 0.9 mcg/L
  2. therapeutic plasma concentrations of digoxin in non CHF ptsĀ (AF and ventricular rate control)
    0.5 - 2.0 mcg/L
  3. bioavailability of tablets
    0.7 - 0.8
  4. bioavailability of elixir
  5. bioavailability of soft gelatin capsule
  6. in the two compartment model Vi is
    plasma and rapidly equilibrating tissues (1/10 Vt)
  7. in the two compartment model Vt is
    large and slowly equilibrating tissues including myocardium
  8. how long is the distribution phase to Vt
    at least 6-8 hrs after last dose, regardless of route of administration
  9. what is the avg Vd
    7.3 L/Kg
  10. what is the formula for Vd
    Vd(L) = (3.8 L/Kg)(wt in kg) + (3.1)(ClCr)
  11. what is total clearance equal to
    Clm + Clr
  12. what is Clt formula in pts without CHF
    0.8(wt in kg) + ClCr
  13. what is the Clt formula for pts with CHF
    0.33(wt in kg) + (0.9)(ClCr)
  14. what does hyperthyroidism do to Clt
    increases it
  15. how does hypothyroidism effect Clt
    it reduces Clt
  16. how long is the half life of digoxin
    2 days with normal renal function and longer with renal impairment
  17. time to sample digoxin
    trough levels at steady state
  18. what is the equation for loading dose
  19. how much of the loading dose do you initially give and how much do you follow up with
    give 1/2 of the loading dose initially, followed by 1/4 of the loading dose q 6hrs
  20. dosing for Clcr <30
    start at 0.125 mg every other day
  21. dosing for ClCr 30 - 80
    start at 0.125 mg every day
  22. ClCr 80 - 120 dosing
    start at 0.25 mg alternating with 0.125 mg qd
  23. dosing for ClCr > 120
    start at 0.25 mg qd
  24. drug used for digoxin toxicity
    digoxin immune fab (DigiFab)
  25. indications of digoxin toxicity
    acute digoxin ingestion (>10 ng/ml)

    chronic ingestions (> 6ng/ml in adults, 4ng/ml in children)

    manifestations of digoxin toxicity (life threatening ventricular arrhythmias, progressive bradycardia, heart block not responsive to atropine)
  26. dosing for acute ingestion of unknown amt
    20 vials IV
  27. dosing for acute ingestion of known amt
    calculate total amount ingested (X 0.8 for tablets)

    calculate number of vials needed (total body load/0.5)
  28. what is the dosing for steady state serum digoxin concentration in adults
    (serum digoxin (ng/mL) X wt (kg))/100