Question

A drug that fully saturates the intestinal transporters required for its absorption necessitates 2.5 hours to be completely absorbed after administering a 100mg dose orally to a volunteer. Once absorbed, the drug has rapid distribution in the body. A 50 mg dose of the drug administered by IV bolus to the same volunteer (in a separate research session) results in plasma concentrations of 1800 ug/L at time 0 hr and 1150 ug/L at time 3.0 hr. If a patient with similar PK parameters took a 250 mg dose of the drug orally, what plasma concentration would you expect at the time 8.0 hours after administration?

Answer 1

Here the body is considered as a single compartment.In which way whenever the drug is administered the drug is only eliminated through the blood only

We can calculate the the plasma concentration of the drug by Vd = D / Co

Where D is the dose of the drug administered and Co is the plasma concentration at the zero hour that means it directly corresponds to the amount of blood contained in the body means V blood

then Vd and V blood are equal

For a human body V blood is 0.08 L/kg

When the time is going on the area of clearance of drug also is increasing

For a drug that is 50 mg at the zero hour the plasma concentration is 1800 ug/L

and during the 3 rd hour it is about 1150ug/L that means eah and every 3 hr 650 ug/L of drug is clearing from the body through the blood

Then we can say that the plasma concentration of 250 mg of drug at 8th hour is

= 2410 - (1950 - 325)

=1625ug/L