This document describes an experiment to calculate various pharmacokinetic parameters from blood concentration data collected after an intravenous bolus injection of ceftriaxone in a newborn infant. A semilogarithmic plot of concentration versus time was constructed to determine the drug elimination half-life. The area under the curve, volume of distribution, and total clearance were then calculated using standard pharmacokinetic equations. The results provide insight into how ceftriaxone is absorbed, distributed, and eliminated in the newborn's body.

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Calculation of Various Pharmacokinetics Parameters after IV Bolus Injection
Experiment Findings · April 2023
DOI: 10.13140/RG.2.2.19815.52645
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2. Biopharmaceutics and Pharmacokinetics Practical
NIMS University Jaipur, Rajasthan 1
Calculation of Various Pharmacokinetics Parameters after IV Bolus Injection
Rahul Pal*1, Prachi Pandey2 (M. Pharm) Pharmaceutics
Department of Pharmaceutics, NIMS Institute of Pharmacy, NIMS University, Jaipur
Rajasthan India
Aim/Object: To calculate various pharmacokinetics parameters from given blood data of IV Bolus
injection (one compartment model).
Objectives: To understand calculation od various pharmacokinetics parameters after one compartment
IV bolus administration following first order elimination.
Requirement: Regular graph paper, semilog graph paper, calculator and pencil etc.
Given Data: Plasma data obtained after a bolus dose of 184 mg of ceftriaxone, a semi synthetic
cephalosporin antibiotic, in a newborn infant is summarized below:
Time (Hr.) 1 6 12 24 48 72 96 144
Conc. (mg/l) 137 120 103 76 42 23 12 3.7
a. Prepare a semilogarithmic plot and estimate the half life of the drug medicament.
b. Estimate the total AUC.
c. Calculate volume of distribution (Vd).
d. Calculate total clearance.
Solution:
Note: if the graph of concentration versus time is plotted on regular graph, the curvilinear plot is
obtained which makes it difficult to calculate slope and hence the semilog plot is used which gives the
linearity and makes it easy and accurate to calculate the pharmacokinetics parameters (Figure. 01).
01. Semilog Plot:
- Plot the graph on semi logarithmic graph paper as the elimination data follows first order
kinetics.
- According to the given data select number of cycles on semilog paper.
- Plot concentration on Y-axis and time on X-axis.
- Mark concentration for respective time on the graph paper.
- Draw a straight lien in such a way that is covers maximum elimination phase points up to
Y-Axis.
- Y-Intercept is the Co concentration.
- Determine slope of the line and calculate elimination rate constant.

3. Biopharmaceutics and Pharmacokinetics Practical
NIMS University Jaipur, Rajasthan 2
02. Elimination Half-life:
- On Y axis near to elimination phase select initial concentration as (C, 20), from that point
draw a straight line which intersects plotted line (Figure. 02). This point would be the first
point of intersection. From intersected draw perpendicular straight line on X axis which
gives the time (t1).
- On Y axis draw a second straight line from half concentration of initial (C/1, 10) which
intersects plotted line. This will be the second point of intersection. From that point
perpendicular on x-axis which gives the time (t2).
- Calculate half-life by subtracting t2 from t1.
01. Elimination rate constant: Calculate elimination rate constant by using slope of line.
Slope =
𝐥𝐨𝐠 𝐂𝟐−𝐥𝐨𝐠 𝐂𝟏
𝐭𝟐−𝐭𝟏
K= -(Slope x 2.303)
02. Elimination half-life: Calculate elimination half life by using following formula:
𝒕𝟏/𝟐=
𝟎.𝟔𝟗𝟑
𝑲
Alternatively, half-life can be determined graphically.
03. Area under curve (AUC): By using concentration at zero-time AUC can be calculated from
following equation (Y intercept is C0 concentration):
AUC0-∞ =
C0
𝐊
04. Clearance: Calculate clearance by using following equation:
Cl = KV

4. Biopharmaceutics and Pharmacokinetics Practical
NIMS University Jaipur, Rajasthan 3
Result: The various pharmacokinetics parameters calculated from given plasma data of ceftriaxone
are given in table below:
Sr. No. Parameters Results
01. Biological half life
02. Elimination rate constant
03. Total AUC
04. Volume of distribution
05. Clearance
Applications:
01. Various pharmacokinetics parameter can be estimated.
02. Pharmacokinetics parameters are very useful in calculating the dose of new drug.
03. Bioequivalence study can be undertaken based on plasma data of various brands.
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