Biological Psychology of Mental Health Reading One
Reading Information
Biological Psychology of Mental Health Week 1: Chapter 4 Pharmacology
Week: 1
Read: 11/08/21
Book: Physiology of Mental Health
Chapter: 4, Pharmacology
Reference: Carlson, N. R., & Birkett, M. A. (2016). Physiology of behavior, global edition. ProQuest
Ebook Central https://ebookcentral.proquest.com
Principles of Psychopharmacology
● Drug: an exogenous chemical not necessary for normal cellular functioning that
significantly alters the functions of certain cells of the body when taken in relatively low
doses
● Exogenous: produced from outside the body
● Drug effects: the changes we observe in an individual;s physiological processes and
behaviour
● The sites of action of drugs: points at which molecules of drugs interact with molecules
located on or in cells of the body, thus affecting some biochemical processes of these
cells
Pharmacokinetics
, ● Pharmacokinetics includes the steps by which drugs are (1) absorbed, (2) distributed
within the body, (3) metabolized, and (4) excreted.
● Most drug metabolizing enzymes are located in the liver
● Absorption: Routes of administration:
○ Intravenous (IV) injection: injection into a vein. Drug is absorbed and distributed
immediately, reaching the brain within a few seconds. Disadvantages: increased
care and skill. If a person is sensitive to a drug, there is little time to counteract
the effects with another drug
○ Intraperitoneal (IP) injection: rapid but not as rapid as IV. Injected through the
abdominal wall into the peritoneal cavity. IP injection is a common method on
small animals.
○ Intramuscular (IM) injection: absorbed in bloodstream through capillaries that
supply the muscle
○ Oral administration
Distribution
● Most important factor that determines the rate at which a drug reaches site of action
within the brain is lipid solubility, or the ability of fat-based molecules to pass through cell
membranes
Metabolism and excretion
● Drugs do not remain in the body indefinitely. Many are metabolized and deactivated by
enzymes, and are all eventually excreted, primarily by the kidneys.
Drug Effectiveness
● To measure the effectiveness of a drug is to plot a dose-response curve
● To do this, individuals are given various doses of a drug, usually defined as milligrams of
drug per kilogram of an individual’s body weight, and the effects of the drug are plotted
● Most drugs have more than one effect
● One measure of a drug’s margin of safety is its therapeutic index. This measure is
obtained by administering varying doses of the drug to a group of laboratory animals or
human volunteers.
● Why do drugs vary in their effectiveness? There are two reasons: sites of action and the
affinity of a drug with its site of action.
● Drugs vary widely in their affinity—the readiness with which the two molecules join
together—for the sites to which they attach. A drug with a high affinity will produce
effects at a relatively low concentration, whereas a drug with a low affinity must be
administered in higher doses. Thus, even two drugs with identical sites of action can
vary widely in their effectiveness if they have different affinities for their binding site
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