The diverse nature of drugs and receptors

Question 1

Physicochemical drugs

Answer 1

Drugs which produce their effects not by binding to a receptor, but due to their physicochemical properties:
-antacids
-laxatives
-heavy metal antidotes
-osmotic diuretics
-general anaesthetics
-alcohol
These tend to need high concentrations to produce their effects, which are rather non-specific.

Question 2

Potency

Answer 2

An expression of the activity of a drug, in terms of the concentration or amount needed to produce a defined effect.

Question 3

Specificity

Answer 3

The capacity of a drug to manifest only one type of action. Can be biological (relating to the receptor) or chemical (relating to the drug).

Question 4

Selectivity

Answer 4

The capacity of a drug to affect one cell population in preference to others.

Question 5

Drug classification

Answer 5

Drugs can be classified in terms of the:

• chemical nature of the drug
• symptoms or diseases in which they are used
• organ system affected
• receptor
• duration of action
• generations
• route of administration

Question 6

Multiple target drugs

Answer 6

One drug does not always just bind to one site-it may have many targets eg. aspirin, steroid hormones, quetiapine. Their effects often result from the interplay of two or more mechanisms. Different doses will bind to different receptors, therefore they may produce different effects.

Question 7

Receptors

Answer 7

In pharmacology, anything that causes a physiological effect when interacting with a drug is a receptor.

Question 8

Types of drug receptor

Answer 8

• enzymes
• ion channels
• transporters (pumps, transport proteins)
• physiological receptors

Question 9

Mechanisms of drug action

Answer 9

• substrates, metabolites and proteins
• DNA/RNA and the ribosome
• various physicochemical mechanisms
• targets of monoclonal antibodies
• many are still unknown…

Question 10

Law of mass action

Answer 10

Also known as Le Chatelier’s Principle/the Equilibrium Law:

A+R↔AR

Question 11

Dissociation constant

Answer 11

Kd=[A][R]/[AR]

Question 12

Agonist/response curve

Answer 12

The relationship between drug concentration and response is:

• continuous, even linear at the beginning
• saturating
• exhibits a threshold

Question 13

Models for drug action

Answer 13

• tissue culture
• organoids
• live animals
• healthy volunteers
• trial patients

Question 14

Stages of drug development

Answer 14

1) Drug discovery
2) Pre-clinical phase
3) Clinical trials
4) Regulatory approval