Biomedical Engineering Reference
In-Depth Information
(b) Write the equation describing the disposition kinetics of the tracer.
(c) Calculate the biological half-life of the tracer elimination, the overall
elimination rate constant, the apparent volume distribution, the coefficient
of distribution, and the duration of action in the tissue.
(d) Comment on the extent of tracer distribution in the body.
10.11 After an intravenous injection of a single 100-mg dose of phenobarbital in a
70-kg patient, the following plasma concentrations were obtained:
t (h)
2
4
6
8
10
12
24
48
72
96
C (mg/L)
1.63 1.30
1.17
1.04
0.94
0.86 0.68
0.54
0.44
0.36
(a) Plot the phenobarbital plasma concentrations versus time.
(b) Determine the number of compartments involved in the disposition of this
drug. Draw a compartmental scheme describing the disposition of this
drug.
(c) Calculate the biological half-life and the volume of distribution.
10.12 Okusanya et al.
[3] reported the compartmental pharmacokinetic analysis of
amprenavir (APV) protease inhibitor using compartmental model. Many po-
tent antiretroviral therapy regimens utilize human immunodeficiency virus
type 1 protease inhibitors as a backbone of HIV therapy. Retrieve [3] and
simulate the model. Discuss the pitfalls in the model.
10.13 Peritoneal dialysis works on the same principle as hemodialysis, but the ex-
change of waste products between the blood and dialysate fluid takes place
inside the body rather than in a machine. The abdomen contains a peritoneal
cavity, which is lined by a thin membrane called the peritoneum. The peri-
toneum is a natural membrane that serves the same purpose in dialysis as
the artificial membrane in a dialysis machine. To accomplish this, the peri-
toneal cavity in the abdomen is filled with dialysis fluid that enters the body
through a permanently implanted tube or catheter. Excess water and wastes
pass though the peritoneum into the dialysis fluid. After a while, this fluid
is drained from the body through the catheter and discarded. Consider the
dialysate fluid and the body to be two well-mixed compartments of volumes
V
D
and
V
B
, respectively. The flux of species
i
across the membrane is
N
i
=
K
i
(
C
bi
C
Di
) where
C
Bi
and
C
Di
refer to solute concentrations in the blood and
dialysate fluid for species
i
, respectively, and
K
i
is an overall mass transfer co-
efficient for species
i
.
−
Suppose that
V
B
is 50L,
V
D
is 2L, the initial solute concentrations in the
dialysate are zero, and the peritoneal membrane area
A
is 2 m
2
. Find the con-
centrations in the dialysate fluid as a function of time for the solutes listed
in the following table with their mass transfer coefficients. Plot your results.
Assume that the blood solute concentrations remain constant and that water
ultrafiltration across the membrane is negligible.
