I'm reviewing this question and think you can't find the answer with the information given.

A patient receives 1g of drug X as a single oral dose. Drug X has a half-life of 12 hours and an oral bioavailability of 40%. What mass (in milligrams) of drug X will still be present in the body 24 hours after a 1g dose?

I think the fact that it is an oral dose means the question is more complicated, involving absorption and distribution of the drug, meaning more factors are needed which are provided in the question.

Is it as easy as: $1000mg \times 0.4 \times 0.5 \times 0.5 = 100mg$

Or there is is more it than that as I suspect? Many thanks!

  • $\begingroup$ I'm no pharmacist at all, but I think you have given yourself a red-herring. The bioavailability surely means that this is the proportion absorbed? $\endgroup$
    – bob1
    May 22 at 21:36
  • $\begingroup$ @bob1 It does but it doesn't tell you over what time-scale the drug is absorbed. You could answer what mass of drug in total will make it into and out of the body (400mg) but not how much at a specific time point (24 hours). $\endgroup$
    – Tom
    May 23 at 11:00

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