Ch 1: Principles of Psychopharm

Question 1

Drugs have biological effects because

Answer 1

They interact with receptors of target tissues

Question 2

Define: Receptor
Define: Ligand

A ligand that are high affinity for the receptor is..

Answer 2

Receptor: large protein molecules located on a cell; INITIAL site of action of all ligands

Ligand: any molecules that binds to a receptor with some selectivity

a ligand that most readily attaches to the receptor

Question 3

Define Antagonist

Answer 3

Capable of binding but produces no physiological change; they ‘block agonist activity” by preventing agonists from binding to the same receptor

ligands with low efficacy

Question 4

Inverse agonists

Answer 4

Binds to a receptor and initiatives a biological response that is opposite of the one produced by the agonist

Question 5

Is binding of a specific ligand to a receptor reversible?

Answer 5

generally, yes

Question 6

What is the number of receptors influenced by?

Answer 6

stimulation

prolonged stimulation - causes down regulation

absences of stimulation - causes up regulation

Question 7

What does a dose-response curve show?

Answer 7

with an increasing dose, the effect also increases in a linear fashion UNTIL maximum effect is reached

Question 8

What is an ED50 dose?

Answer 8

a dose that produces a half-maximal effect (50%)

The MORE potent drug is the one with a lower ED 50

Question 9

What is the TI?

Answer 9

Therapeutic Index

Compares the TD50 (50% toxic dose ) with the ED 50 - provides a measurement for drug safety

Question 10

What effect do competitive receptor antagonists have on the potency of an agonist? What effect does this have on the dose-response curve?

Answer 10

Competitive receptor agonists REDUCE potency of an agonist

Dose-response curve shifts (parallel) to the right, with NO change in maximum effect

Question 11

What effect can biobehavioural interactions of drugs produce?

Answer 11

Physiological antagonism

Additive effects

Potentiation

Question 12

Potential results of chronic drug use:

Answer 12

1) may lead ro a reduction in biobehavioural effects (TOLERANCE)

or sometimes

2) SENSITIZATION

Question 13

What is cross tolerance?

Answer 13

When repeated use of one dru reduced the effectiveness of a second drug

Question 14

Is tolerance reversible? What is this dependent on?

Answer 14

Generally reversible

Dependent on: dose, frequency of use, and drug-taking environment

• not all drugs induce tolerance
• not all effects of a given drug undergo tolerance to the same extent/same rate

Question 15

What is pharmodynamics?

What is pharmodynamic tolerance?

Answer 15

Pharmacodynamics: the study of the physiological and biochemical interaction of drug molecules with target tissue, which is ultimately responsible for drug effects

Tolerance: the adaptation of the nervous system to continued presence of the drug by increasing or decreasing receptors or producing other compensatory intracelluar processes

Question 16

What is behavioural tolerance?

Answer 16

When learning processes and environmental cutes contribute to the reduction in drug effectiveness

e.g. pavlovian conditioning/operant conditioning

Question 17

What is sensitization? How is it difference from tolerance?

Answer 17

Dependent on dose, intervals between treatments and drug-taking environment

Cross-sensitization with other drugs can occur

UNLIKE TOLERANCE:

• sensitization is not readily reversible
• persists long periods of abstinence caused by LONG-TERM physiological changes to the cells.

Question 18

Define: Psychopharmacology

Answer 18

The scientific study of the actions of drugs and their effects on a living organism : specifically the drug-induced changes on mood, thinking and behaviour

Question 19

Define: Phamacokinetics

Answer 19

Interacting Pharamokinetic factors determine HOW MUCH free drug is in the blood (bioavailability)

5 pharmokinetic factors that influence the bioavilability of the drug:

1. method of admin
2. rate of absorption/distribution
3. binding at inactive sites (drug depots) e.g plasma proteins, bone, fat (
4. biotransformation (INACTIVATION - occurs in the liver)
5. excretion

Question 20

What are lipid soluble drugs?

Answer 20

NOT ionized, and readily pass through fatty membranes, through passive diffusion based on concentration gradient (higher to lower concen)

Lipid solubility increases the absoprtion of a drug into the blood and determines readiness for brain entry

ONLY lipid soluble drugs can enter the brain

Question 21

What is the importance of the blood-brain barrier

Answer 21

ONLY lipid soluble drugs can enter the brain

Drug distribution is usually determied by volume of blood flow to the tisues EXCEPT for the brain due to specialized brain capilarries

Question 22

Effect of drugs are determined by:

Answer 22

1) How much of drug reaches target site

2) How quickly the drug reaches that site

Question 23

What factors is absorption dependent on?

Answer 23

Absorption: movement or drug from site of admin to blood circulation; mostly occurs in small intestine

• method of admin
• soluability and ionization of the drug
• individuals differences: age, sex, body size

Question 24

Define Half Life

Answer 24

HALF LIFE: the rate at which a drug is removed from the body
Drug clearance usually occurs by first-order kinetics - where a CONSTANT fraction of the free drug is removed during each time internal (the internal is called the half life)
some drugs have zero-order kinetics : clearance occurs at constant rate regardless of drug concentration

Important because it determines the internals required between doses

Question 25

What is enzymatic drug metabolism/biotransformation?

Answer 25

Occurs in liver - produces chemical change to drug molecule that makes in inactive and more water soluable

Cytochrom P450 family of enzymes is the most important type of liver enzyme for transforming psychotropic drugs

Question 26

Describe the process of drug metabolism

Answer 26

Phase 1: oxidation, reduction or hydrolysis to produce a ionized metabolically that may less, equally or more active that parent drug. (NONSYNTHETIC)

Phase 2: Conguation of drug with a simple molecule provided by the body e.g. glucuronide or sulfate. Products are ALWAYS inactive and more water soluble (SYNTHETIC).

Question 27

Contrast drug action vs drug effects

Answer 27

Drug action: specific molecular changes produced by drug when it binds to a target site/receptor

Drug effects: when molecular change leads to more widespread physiological/psychological effects

Site of drug action may not be the same as site of drug effects

Question 28

Contrast drug action vs drug effects

Answer 28

Drug action: specific molecular changes produced by drug when it binds to a target site/receptor

Drug effects: when molecular change leads to more widespread physiologica/psychological effects

Site of drug action may not be the same as site of drug effects

Question 29

Contrast specific drug effect with non-specific drug effect

Answer 29

Specific: based on physical and biochemical interactions of a drug with target site in living tissue

Nonspecific drug effects: based on unique individual’s background e.g. mood, expectations, attitude et.c

Question 30

What is depot binding? What are the effects?

Answer 30

Binding of a drug to an inactive site e.g. plasma, bone, fat

Has significant effects on the magnitude and the duration of the drug action

• reduces concentration of the drug at action site due to lower concentration of free circulating drug
• onset of drug may be delayed

Can also cause overdose because binding to inactive sites is over nonselective: therefore increasing competition between drugs : may results in a higher blood concentration than anticipated

• cannot be processed by liver