Basic Pharmacology

Question 1

Define drug

Answer 1

Chemical substance that interacts with a receptor to produce a physiological response

Question 2

Define receptor

Answer 2

Region of tissue or a molecule in a cell membrane which responds specifically to a particular neurotransmitter, hormone, antigen or other substance

Question 3

Agonist

Answer 3

A drug that is able to bind to a receptor to mimic the action of a hormone, or of a transmitter and induce a cellular/physiological response

Has affinity for receptor and efficacy
Full or partial

Question 4

Equilibrium will be reached when…

Answer 4

…rate of reaction of drug and receptor coming together and rate of reaction splitting apart will be equal

Question 5

What is simple occupancy theory

Answer 5

The intensity of a response to a drug is proportional to the number of receptors the drug occupies

Question 6

If a drug achieves occupancy as a lower concentration than another dug it is said to have

Answer 6

Higher affinity

Question 7

Affinity

Answer 7

• The strength of the binding between drug and receptor
• High affinity on its own does not necessarily produce a response
• Affinity influences horizontal position of the dose occupancy curve
• Characterised by the equilibrium dissociation constant (Kd) – ratio of rate of constants for reverse and forward reaction between drug and receptor

Question 8

Efficacy

Answer 8

• The maximum effect that the drug is capable of
• Linked to the capability of the drug to elicit a response
• Used to be referred to “intrinsic activity”

Question 9

What does potency mean

Answer 9

Depends on both affinity and efficacy
Dose required to produce a specific intensity of response. ED50 can be a good indicator of potency

So a higher potent drug would be one that can gain the same effect with a lower dosage

Question 10

What does ED50, TD50, LD50 mean

Answer 10

ED50 = Effective dose for 50% of ppl taking the drug
TD50 = dose which causes toxicity in 50% of people taking the drug
LD50 = dose which causes death in 50% of those given the drug

Question 11

How to calculate therapeutic index

Answer 11

TD50 / ED50

Don’t want a narrow theraputic index

Question 12

Antagonist

Answer 12

Block agonist from working
No response in efficacy but high affinity

Effect can be overcome if you increase the agonist concentration

Maximum possible response still possible but now requires greater concentration to produce same response

Question 14

Irreversible antagonist

Answer 14

Permanently deactivates receptor until body resynthesises again

Question 15

What is meant by administration

Answer 15

The path in which the drug enters the body

Question 16

What is Cmax

Answer 16

Amount of drug being placed into the blood stream exceeds the amount of drug which is taken out of the bloodstream again

Question 17

What is tmax

Answer 17

Cmax AKA T max is the amount of time it takes following the drug being administered until it reaches maximum concentration in the plasma

Question 18

What are the types of administration methods

Answer 18

Enteral:
- sublingual
- buccal
- oral
Rectal

Parenteral:
- injections
- Inhalations
- cutaneous

Question 19

Enteral route

Answer 19

Have to pass across epithelium lining the GI tract

Question 20

Parental route

Answer 20

Many cross epithelium e.g. skin, lung or may avoid epithelium if they are injected

Question 21

Enteral route: sublingual

Answer 21

• under the tongue
• allow the drug to enter systemic circulation without first passing through the liver
• rapid means of absorption
• ideal for lipid soluble drugs which would otherwise be metabolised by liver

Question 22

Enteral: buccal

Answer 22

Med placed between the px check and gum and not swallowed
Avoids metabolism by liver like sublingual
Presence of saliva enhances dissolution of the drug so px may not appreciate the taste

Question 23

What is the first pass effect

Answer 23

First pass effect – the concentration of drug which is available to reach the systemic circulation is greatly reduced because of the process of absorption that it goes through in the gut wall and liver.

Buccal or sublingual methods avoid first passing through as don’t require being swallowed

Question 24

If a drug does undergo first passing through effect then…

Answer 24

…a higher dose will be needed compared to if administered differently

Question 25

Capsules

Answer 25

Can be made hard like gelatine with dry powder inside or contents is an oil and capsule is soft

Question 26

What’s an enteric coating

Answer 26

Barrier applied to tablet to help protect it from acidity of stomach. Will break down rapidly in other environments

Question 27

Enteral: rectal

Answer 27

Useful for px who vomits Absorption in slow and unreliable ad there is no microvilli

Question 28

Parenteral: Intravenous injection (fastest and most certain route)

Answer 28

(fastest and most certain route) - infusion of liquid substances directly into vein - dose reaches systemic circulation immediately Desirable when rapid response is required Disadvantages: may be difficult to find suitable vein to inject into, requires training to be able to administer. Can be expensive because procedures ensuring sterility need to be adhered and can increase cost of preparation, transport and storage of medication.

Question 29

Parenteral: subcutaneous injection

Answer 29

Administered into subcutis (layer of skin beneath the dermis and epidermis) Yellow/pale area Used to administer vaccine and meds such as insulin and morphine Px can administer themselves Slow absorption

Question 30

Intramuscular injection

Answer 30

Deeper injections than subcutaneous Made directly into muscle Faster rate of absorption Trained personnel only

Question 31

Parenteral: inhalation

Answer 31

- inhale the drug - delivers to lungs - large surface area and good blood supply - Rapid absorption - bypasses liver so avoids first pass metabolism E.g. salbutamol

Question 32

What is meant by absorption

Answer 32

Transfer of the drug from site of administration into bloodstream

Question 33

How is oral med absorbed and how is intravenously med absorbed

Answer 33

Dissolved and then absorbed Intravenous - cross several semipermeable membranes to reach bloodstream

Question 34

What kind of drug is able to have a pharmacological effect

Answer 34

Only FREE drug molecules are able to have a pharmacological effect So when molecule is bound unable to have any effect Drugs that are bound to the proteins act as a reservoir/ storage facility for drug molecules. No metabolise or excretion just remain in bloodstream

Question 35

Amount of drug which is free compared to amount that is bound influenced by:

Answer 35

• Concentration of drug • Availability of plasma proteins • Presence of any other drugs trying to bind to same proteins

Question 36

What’s the formula to work out volume of distribution

Answer 36

Total amount of drug in the body/ drug blood plasma concentration

Question 37

What type of drugs are difficult to excrete

Answer 37

Lipid soluble

Question 38

What are the sites of metabolism

Answer 38

- walls of intestine Lungs Kidney Plasma Main site = liver

Question 39

Metabolism can be divided into what 2 phases

Answer 39

Functionalisation - oxidation, reduction or hydrolysis of drugs - increases hydrophilicity Conjugations - metabolites conjugated with a charged species which increases the hydrophilicity

Question 40

What are factors that affect metabolism

Answer 40

Type of drug Enzyme inhibitor Age - slower in babies/elderly Nutrition Liver diseases - reduced blood flow to liver Genetic variation - px not able to produce the enzyme

Question 41

What are prodrugs

Answer 41

- inactive when administered until metabolised - Converted into active metabolite

Question 42

Why give a drug in the form of a prodrug?

Answer 42

Rapidly metabolised and u wanna slow that down Want to make sure duration is enhanced Adjust polarity and lipophicility of drug in order to influence way it is absorbed

Question 43

Enzyme induction

Answer 43

- increased activity of drug metabolising enzymes - reduces amount of un-metabolised drug - reduces plasma conc and decrease efficacy - can increase or decrease drug toxicity depending on toxicity or metabolites

Question 44

Enzyme inhibition

Answer 44

Decreased activity of drug metabolising enzymes Can prolong effect of drug Increased drug conc may lead to adverse reactions

Question 45

What is the major route of excretion of drugs

Answer 45

Via kidney also build/intestine Other routes: pulmonary excretion involving lungs, saliva, breast milk

Question 47

What makes excretion of drugs difficult

Answer 47

- weight off drug - if drug highly lipid soluble harder - plasma protein bound - larger molecule - age - kidney diseases - dehydration - decrease in blood volume so dose of drug would be altered until px was rehydrated