Drug Properties

Question 1

Pharmacodynamics

Answer 1

(The study of) mechanisms of action for a drug (its biochemical/physiological effects).

Question 2

Binding Affinity and Binding Efficacy

Answer 2

Binding Affinity: The strength of the drug binding to a receptor.
Binding Efficacy: The ability of the drug bound receptor to produce a response.

Agonists have both efficacy and affinity.
Antagonists have no efficacy, only affinity.
The lower the Kd value, the greater the affinity.

Question 3

Drug Tolerance

Answer 3

A diminished response to a drug after a repeated exposure to said drug.

Question 4

Metabolic Tolerance

Answer 4

Prevents the drug from reaching its site of action.

Eg. Enzymes break a drug down more rapidly (one’s metabolism has adjusted to the drug).

Question 5

Pharmacodynamic Tolerance

Answer 5

Reduces the responsiveness at the drug’s site of action.
Eg. Decreased receptors available for a drug after repeated usage, or the drug may no longer even activate said receptors.

Question 6

Behavioural Tolerance

Answer 6

Also known as context specific tolerance. When tolerance occurs in the same specific environment the drug is being taken.

This is a classical conditioning mechanism.

Question 7

Acute Tolerance

Answer 7

When drug tolerance is built very quickly.

Drugs that one can develop acute tolerance to include nicotine, heroin and LSD.

Question 8

Drug Sensitization

Answer 8

An increased response to a drug after a repeated exposure to said drug.

This can happen with cocaine, for example, and is known as cocaine sensitization.

Question 9

Dependence

Answer 9

Someone is dependent on drug if when the drug is no longer in their system, withdrawals happen.

Not necessarily the same as addiction. For example, going off caffeine can cause withdrawals, but caffeine is not considered addictive.

Question 10

Heroin Rat Study

Answer 10

Showed that rodents dependent on heroin were more likely to overdose if the heroin was administered in a new environment vs an environment the heroin had already been administered in.

Question 11

Pharmacokinetics

Answer 11

How a drug passes through the body.

Question 12

Four Stages of Pharmacokinetics

Answer 12

1. Absorption: The drug is administered, then absorbed into the bloodstream.
2. Distribution: Refers to the passage of drug from the bloodstream into the organs. It must penetrate specific membranes to exert its effect(s) on the brain and/or body.
3. Biotransformation: The drug is broken down into metabolites by enzymes.
4. Elimination: The drug and/or its metabolites are eliminated from the body.

Question 13

Routes of Administration

Oral (PO/Per os)

Answer 13

Oral administration is typically self-administered. Absorption is slow and highly variable.

Question 14

Routes of Administration

Intravenous (IV)

Answer 14

Injection of a drug into a vein. Rapid, and has most accurate blood concentration (dosage can be fine tuned).

Question 15

Routes of Administration

Intramuscular (IM)

Answer 15

Injection of a drug into the muscle. Has a slow and even absorption.

Question 16

Routes of Administration

Subcutaneous (SC)

Answer 16

Injection between the skin and muscle. Slow and prolonged absorption, can be variable.

Question 17

Routes of Administration

Inhalation

Answer 17

Rapid onset drug absorption. Can irritate nasal passages, small particles may damage lungs.

Question 18

Drug pKa and environmental pH

Answer 18

Measure of acidity.

Question 19

Bioavailability

Answer 19

The drug’s ability to reach the brain/site of action.

Small/uncharged/liquid-soluble drugs will usually cross the blood-brain barrier more easily.

Question 20

Blood-brain barrier

Answer 20

A membrane between the blood and inner fluids of the brain.

Question 21

Non-specific binding

Answer 21

A drug that binds to an unintended receptor.

Question 22

First-pass metabolism

Answer 22

When a drug is metabolized in a specific region of the body.

Question 23

Active metabolites

Answer 23

The result when a drug is metabolized into a modified form that has effects within the body.

Question 24

Prodrugs

Answer 24

Drugs that are metabolized into an active form once they enter the body.

The drug does not act on the body directly, until it is metabolized.