Download A Primer on Pharmacological Processes

A Primer on Pharmacological Processes
Daniel Kaplin, MA
College of Staten Island
City University of New York
A Primer on Pharmacological Processes
In a change from my traditional writing about the application of pharmacological agents
to psychological disorders, I would like to discuss how psychotropic medications operate in the
brain. I will focus on three important concepts: (a) Pharmacokinetics, (b) Pharmacodynamics,
and (c) Pharmacometrics.
Basic Principles
Pharmacokinetics refers to the movement of a drug through the body (Kalat, Schwartz, &
Jessell, 2000). It is broken down into the following ADME sequence: (a) absorption or
administration, distribution, metabolism, excretion (Guttendorf, 2006). Absorption refers to the
way the drug is entered into the bloodstream. Distribution refers to the how the drug is
transported to its effector site. Metabolism refers to the breakdown of the drug. Lastly, excretion
is the way that the body eliminates waste (Guttendorf, 2006). Of notable interest are ED/LD
curves. ED, or Effective Dose, refers to the amount of a drug needed to have a desired effect.
LD, or Lethal Dose, the amount of a drug needed to cause death. Together, these form the
therapeutic index.
Pharmacodynamics refers to the changes to the brain and body as a result of taking a
pharmacological agent (Kalat et al., 2000). For example, a drug that increases the likelihood of a
neurotransmitter to fire is referred to an agonist. An antagonist, on the other hand, is a chemical
that decreases the likelihood of a neurotransmitter. Other concerns related to pharmacodynamics
are adverse side effects.
Pharmacometrics are ways that we study a drugs response (Kalat et al., 2000). Generally,
one must know the pharmacokinetics and pharmacodynamics of drugs to fully appreciate
pharmacometrics. These help us appreciate variability in responsiveness to a drug
Application to Alcohol
In terms of alcohol, it is general ingested orally, where it is distributed into the blood
stream. It then goes to its site of metabolism, the liver, where it begins to breakdown.
Afterwards, it is generally excreted though urination (Feldman, Meyer, and Quenzer, 1997).
This reflects the movement of alcohol through the body. In terms of pharmacodynamics,
alchohol operates primarily on the inhibitory neurotransmitter called GABA. This results in
inhibition of inhibition, or disinhibition. Once this occurs, the brain regions associated with
speech, motor coordination, and decision making can become adversely effected. In terms of
pharmacometrics, one might ask about how weight, gender, ethnicity and so forth influence the
reaction to alcohol.
References
Feldman, R. S., Meyer, J. S., & Quenzer, L. F. (1997). Principles of neuropharmacology.
Sunderland, MA: Sinauer Associates.
Guttendorf, R. J. (2006). The Emerging Role of A.D.M.E. in Optimizing Drug Discovery and
Design. Retrieved from http://www.netsci.org/Science/Special/feature06.html
Kalat,E. R., Schwartz,J. H., & Jessell, T. M. (2000). Principles of neural science (4th edition),
New York: McGraw Hill