Posted: May 16th, 2016

Draw a diagram of a compartmental model that describes the plasma disposition of the drug and indicate any relevant rate constants.

5.    Drug X is administered as an IV bolus dose of 100mg and the following plasma concentrations were obtained with time:
Time (h)    0.25    0.5    1.0    3.0    5.0    7.0    10.0
Plasma Concentration (mg/L)    2.6    2.4    2.1    1.2    0.75    0.45    0.2
Calculate the volume of distribution, plasma half-life and clearance of X.
X was subsequently administered via the oral route at a dose of 200mg as both an aqueous solution and as a formulated product. The measured areas under the plasma concentration time curves were 14.3 mg/L.h and 12.6 mg/L.h for the solution dose and formulated product respectively.

Using this data calculate the relative and absolute bioavailability of X.
6.    Drug W on IV administration to an experimental animal at a dose of 10mg/kg (animal weight 2.3kg) gave the following plasma concentrations with time:
Time (h)    0.1    0.25    0.5    0.75    1.0    1,5    2.0    3.0    4.0
Plasma Concentration
(mg/L)    4.2    3.2    2.3    1.8    1.5    1.2    1.09    0.88    0.71

Using the above data:
(a)    Draw a diagram of a compartmental model that describes the plasma disposition of the drug and indicate any relevant rate constants.
(b)    Write an equation describing the plasma concentration versus time curve (use numbers rather than symbols as much as possible).
(c)    Calculate the values of the rate constants you have indicated in part (a).
(d)    What is the terminal half-life of drug W?
(e)    What is the volume of distribution of W and what is the initial dilution volume (volume of the central compartment)?
(f)    Calculate the area under the plasma concentration versus time curve and compare this value with that obtained using the trapezoidal method.