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Al-Achi, A.

Campbell University
CU FIND
Pharmacy Pharmacy and Health Sciences, College of
2018
Are Thermodynamic Principles Important to Teach
in Pharmacy Education?
A. Al-Achi
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Part of the Pharmacy and Pharmaceutical Sciences Commons
This Article is brought to you for free and open access by the Pharmacy and Health Sciences, College of at CU FIND. It has been accepted for inclusion
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Recommended Citation
Al-Achi, A., "Are Thermodynamic Principles Important to Teach in Pharmacy Education?" (2018). Pharmacy. 597.
https://cufind.campbell.edu/pharmacy/597
Editorial Open Access
Clinical Pharmacology 
& Biopharmaceutics Clini
ca
l P
ha
rm
aco
logy & Biopharm
aceutics
ISSN: 2167-065X
Al-Achi, Clin Pharmacol Biopharm 2018, 7:1
DOI: 10.4172/2167-065X.1000e130
Volume 7 • Issue 1 • 1000e130Clin Pharmacol Biopharm, an open access journal
ISSN: 2167-065X
Are Thermodynamic Principles Important to Teach in Pharmacy Education?
Antoine Al-Achi*
Campbell University College of Pharmacy & Health Sciences, P.O. Box 1090, Buies Creek, NC 27506, USA
Editorial
Many physical and chemical concepts are highly applicable in 
pharmacy education. Also, biological principles play a significant role 
in understanding the fundamentals of drug action and its absorption, 
distribution, and elimination from the body. Among the physical 
and chemical information that often taught in pharmacy programs 
are those related to thermodynamics. In particular, courses in 
biochemistry, physiology, and pharmaceutics can use thermodynamic 
concepts to explain the various phenomena in these fields of study. For 
example, the diffusion of the drug through a biological membrane is a 
spontaneous process (the word spontaneous implies that the process is 
natural and irreversible). When drug molecules move from an area of 
high drug concentration (e.g., the intestine) to an area with low drug 
concentration (the blood circulation), this pathway is spontaneous. It 
occurs because all natural systems change in such a way so that further 
changes are less possible or not possible at all (i.e., they approach a 
state of equilibrium). These principles can explain the direction of the 
process, and often they are more applicable nearby an equilibrium 
point instead of being far away from it. Also, they are more pertinent 
to isolated closed systems than those encountered in physiological 
processes. So the dilemma that faces a pharmacy educator is that how to 
bring these principles into actual practice. It is perhaps best to explain 
to students about what the various thermodynamic measures mean 
rather than how to calculate them from observed data. For example, 
the enthalpy, as a thermodynamic measure, is defined by the amount 
of heat absorbed or released by a system while the system undergoes 
a change [1]. This is useful to a student-pharmacist who wants to 
understand how drug molecules dissolve in a solvent system. During 
dissolution, the system initially absorbs heat from the environment to 
break down molecular drug aggregates and in the final step the drug 
molecules thus released can be deposited in the free cavitation available 
in the solvent. During that deposition of drug molecules in the cavity of 
the solvent, the system gives up the heat.1,2 Another important measure 
in thermodynamics is the entropy. It is the thermodynamic measure 
for the amount of energy that is not useful to do work. The higher the 
entropy of a system, the closer that system to its point of equilibrium 
and the lower its capacity to do work [1-3]. The pharmacy educator may 
use for example the states of matter to illustrate the concept of entropy 
to his students. In this case, a crystalline solid has the lowest entropy, 
followed by the liquid solute, and then the gaseous/vapor phase of the 
solute where the entropy value is found at its highest [1,2]. Another 
illustration for a thermodynamic measure is the concept of free energy. 
Generally speaking, the free energy of a system is the amount of energy 
available to a system to perform work. This often is accompanied 
initially by the system absorbing heat from the environment. Since the 
free energy is being utilized by the system to do work, it is expected 
therefore that it decreases in value as the system is doing work. Thus, 
the difference in free energy must be negative if the system undergoes 
a spontaneous reaction. If the change in free energy is positive, then 
no spontaneous response can happen. Another pharmaceutical 
application of the free energy is in the interfacial phenomenon. The 
ability of one liquid to spread on the surface of another liquid, when 
this occurs, an amount of free energy is utilized by the system for the 
spreading to occur. This energy loss by the system is quantified by the 
difference between the work of adhesion between the two liquids, and 
the work of cohesion of the fluid which is spreading onto the surface. 
By convention, when the work of adhesion is greater in value than the 
work of cohesion, spreading is possible. 
Instructions in this area may also expand to physiological 
applications where enthalpy, entropy, and free energy can explain 
whether the process is enthalpy-driven or entropy-driven. Assume that 
a researcher measures the concentration of potassium ions outside the 
cell (extracellular fluid) as opposed to that found inside the cell. If the 
initial concentration of potassium in the extracellular fluid was A1 and 
that at a final point (i.e., equilibrium or another time point) was A2, 
then the [2,4] equilibrium constant for this process may be written as
1 2Keq A A=                      (1)
In turn, the equilibrium constant may be calculated at different 
temperatures, and a linear equation may be found between the natural 
logarithm of Keq and the inverse of temperature:
1Hln Keq constant
R T
∆  = − + 
 
                  (2)
The constant of integration may be estimated from:
G H T S∆ = ∆ − ∆                  (3)
Where, ∆G is the change in free energy, ∆H is the enthalpy, and 
∆S is the entropy. The temperature, T, in the equations above must be 
stated in Kelvin and R is the gas constant.
Also, the change in free energy and Keq are related by the following 
expression:
G nRTInKeq∆ = −                                             (4)
From equations (3) and (4) above and for one mole of the substance 
(n = 1), we can write,
nRTInKeq H T S− = ∆ − ∆                 (5)
1H DSInKeq
R T R
∆  = − + 
 
                                      (6)
*Corresponding author: Antoine Al-Achi, Campbell University College of Pharmacy 
& Health Sciences, P.O. Box 1090, Buies Creek, NC 27506, USA, Tel: (910) 893-1703 
x1703; E-mail: alachi@campbell.edu 
Received January 25, 2018; Accepted February 02, 2018; Published February 
05, 2018
Citation: Al-Achi A (2018) Are Thermodynamic Principles Important to Teach in Pharmacy 
Education? Clin Pharmacol Biopharm 7: e130. doi: 10.4172/2167-065X.1000e130
Copyright: © 2018 Al-Achi A. This is an open-access article distributed under the 
terms of the Creative Commons Attribution License, which permits unrestricted 
use, distribution, and reproduction in any medium, provided the original author and 
source are credited.
Citation: Al-Achi A (2018) Are Thermodynamic Principles Important to Teach in Pharmacy Education? Clin Pharmacol Biopharm 7: e130. doi: 
10.4172/2167-065X.1000e130
Page 2 of 2
Volume 7 • Issue 1 • 1000e130Clin Pharmacol Biopharm, an open access journal
ISSN: 2167-065X
Thus, the constant of integration is obtained from the y-intercept 
of the straight line between ln Keq vs. (1/T). Therefore, by studying Keq 
value at different temperatures, the values for ∆H and ∆S will be readily 
available. Replacing these values in equation (3) above would estimate 
the change in free energy at a given temperature, T. From equation (3), 
a higher positive value for S and a higher negative value for H allow 
the value of ∆G to be more negative, and thus a spontaneous reaction.
The principles of thermodynamics may be introduced in a 
pharmacy program at many points of the curriculum. Courses such 
as biochemistry, pharmaceutics, and physiology are all candidates 
where these concepts may be taught. Emphasis on understanding the 
measures and how they relate to each other is more important than to 
show actual calculations for these measures. Perhaps the instructions 
may be supplemented with scientific articles where students can read 
how these thermodynamic measures helped in delineating a particular 
pharmaceutical process (e.g., distinguishing between the various 
polymorphic forms of a medicinal substance) [3].
References
1. Amiji MM, Sandmann JB (2003) Applied Physical Pharmacy. 
2. Martin M, Swarbrick J, Cammarata A (1983) Physical Pharmacy. 
3. Al-Achi A, Gupta M, Stagner W (2013) Integrated Pharmaceutics.
4. Raffa BR (1999) Minireview: (Extra) Thermodynamics of the Drug-Receptor 
Interaction. Life Sciences 65: 967-980.


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