Vd = amount of drug in body / plasma drug concentration.
Amount of drug in body = 80mg
Plasma drug concentration = 4 micrograms/mL = 4mg/L
Vd = 80mg/(4mg/L) = 20L
Distribution half-life is 3 minutes so after 30 min we can assume the drug is maximally distributed. Elimination half-life is 24 hours so we can assume a neglible amount of drug lost
submitted by skinnynomore(7), 2019-05-20T09:54:19Z
They’re giving a lot of confusing extra information here, maybe to trip us up. They just want volume of distribution, simple as that.
Vd = [drug administered] ÷ [plasma drug concentration]
First convert it all to
g/L
because this is how the answer will be:administered:
80 mg = 0.08 g
plasma concentration:4 ug/ml = 0.004 g/L
Thus,
Vd = 0.08 grams ÷ 0.004 g/L = 20 L
Clearance of drug is not a huge factor because the half life is so long that the drug is distributing before significant clearance occurs.