Basic Pharmacology

Question 1

Evaluate the 2 routes of drug administration- enteral and parental routes (20)

Answer 1

Enteral routes of administration involves drugs being absorbed via the gastrointestinal tract such as oral and rectal routes. For example, oral ingestion involves a low risk of infection as the gastrointestinal tract has many barriers to infection that are already present. However, drugs need to have a special coating so that it reaches the gut undamaged by the harsh acidic environment in the stomach. Also, a large proportion of the drug is lost through first pass metabolism.

On the other hand, parental routes are where the drug doesn’t get absorbed via the gut. For example, topical creams have local effects and are suitable to long period administration. There is limited first pass metabolism and usually a low infection risk. However, there can be skin irritation, the drug must be lipid soluble, and the drug must have a small molecular size. Injections are also a parental route. This completely avoids first pass metabolism and it causes the drug to have rapid bioavailability. But, there is a risk of infection because we are breaking the surface of the skin.

Question 2

What is the enteral administration route

Answer 2

Enteral routes of administration involves drugs being absorbed via the gastrointestinal tract such as oral and rectal routes. For example, oral ingestion involves a low risk of infection as the gastrointestinal tract has many barriers to infection that are already present. However, drugs need to have a special coating so that it reaches the gut undamaged by the harsh acidic environment in the stomach. Also, a large proportion of the drug is lost through first pass metabolism.

Question 3

What is the parental administration route

Answer 3

parental routes are where the drug doesn’t get absorbed via the gut. For example, topical creams have local effects and are suitable to long period administration. There is limited first pass metabolism and usually a low infection risk. However, there can be skin irritation, the drug must be lipid soluble, and the drug must have a small molecular size. Injections are also a parental route. This completely avoids first pass metabolism and it causes the drug to have rapid bioavailability. But, there is a risk of infection because we are breaking the surface of the skin.

Question 4

DESCRIBE THE DISTRIBUTION PROCESS OF A DRUG. Include knowledge around protein binding, blood flow to the tissues, and membrane permeation (20)

Answer 4

Distribution – there are 3 factors affecting distribution: protein binding, blood flow to the tissues, and membrane permeation.

In terms of protein binding, an ingested drug can bind to plasma proteins in the plasma water, but only the unbound fraction of the drug can cross membranes or bind to receptors. Drugs are only bioavailable if they are unbound, because these are the molecules that are small enough to diffuse through capillary walls and so produce a pharmacological effect. We need to be aware that a drug might have more of a profound effect in a patient who is malnourished because more of the drug will be unbound and therefore bioavailable.

The rate at which a drug gets to a blood rich area of the body is much faster than in an area with less blood supplying it.

According to Fick’s law, the higher the surface area of a membrane, the faster the exchange of a substance. Also, uncharged ions diffuse more efficiently than charged ions, so non-ionised drugs will have better access to membrane bound compartments. Finally, a drug needs to be lipophilic because the area inside the membrane is hydrophobic, so a hydrophilic drug wont be able to pass through.

Question 5

What are the factors affecting drug distribution

Answer 5

there are 3 factors affecting distribution: protein binding, blood flow to the tissues, and membrane permeation.

Question 6

Describe the protein binding of a drug

Answer 6

In terms of protein binding, an ingested drug can bind to plasma proteins in the plasma water, but only the unbound fraction of the drug can cross membranes or bind to receptors. Drugs are only bioavailable if they are unbound, because these are the molecules that are small enough to diffuse through capillary walls and so produce a pharmacological effect. We need to be aware that a drug might have more of a profound effect in a patient who is malnourished because more of the drug will be unbound and therefore bioavailable.

Question 7

What affects the rate of distribution

Answer 7

The rate at which a drug gets to a blood rich area of the body is much faster than in an area with less blood supplying it.

Question 8

What does hydrophobic mean

Answer 8

when something repels or doesn’t mix with water

Question 9

What does hydrophilic mean

Answer 9

when something has a tendency to mix with, dissolve in, or get wet my water. drug needs to be lipophilic because the area inside the membrane is hydrophobic, so a hydrophilic drug wont be able to pass through.

Question 10

What does lipophilic mean

Answer 10

when something tends to combine with or dissolve in lipids and fats. drug needs to be lipophilic because the area inside the membrane is hydrophobic, so a hydrophilic drug wont be able to pass through.

Question 11

Describe what a drug is

Answer 11

a chemical substance of known structure, which when administered to a living organism produces a biological effect. could be given to a human, farm animal ect. A drug dissolves randomly into the blood and is pumped around the whole body, but it will only have an effect in the areas of the body where the matching receptors are present. Some receptors might only be found in one area of the body or on one type of tissue cell, this affects where the drug has its effect.

Question 12

Describe what a medicine is

Answer 12

any substance or combination of substances presented as having properties of preventing or treating disease in human beings. A substance used for a therapeutic effect. Some medicines don’t contain any drugs such as herbal ones. An example of a medicine is paracetamol when it is taken to relieve a headache.

Question 13

What does the term therapeutics mean.

Answer 13

use of drugs to diagnose, prevent and treat illness (and/or pregnancy) i.e., the medical use of drugs. (drugs that are not used therapeutically are ones that are used in research or recreationally)

Question 14

What is meant by the formulation of a drug. Why is a formulation used?

Answer 14

how the drug is ‘packaged’ e.g., different chemical substances, including the active drug, are combined to produce a medicine. there could be binders, bulking agents ect that are used as a veicle for the drug to get into the body with. they are used because the drug in its oure form might be used in too smalll of a dose to make a tablet out of. there are also coatings for tablets that are used to protect the drug itself within the formulation, such as anti-adherant coatings to allow the pills not to stick to eachother. waxy or polymer coatings protect the drug from the acid environment in the stomach, so they can get to the intestine to be absorbedd there. preservatives are added to give it shelf life.

Question 15

What is an excipient?

Answer 15

is something that carries the drug. What a drug is bound up with to make it ready to use.

Question 16

What is a ligand?

Answer 16

a molecule that binds to a receptor, such as drugs, hormones, and neurotransmitters. Exogenous ligands are ones produced outside of the body, such as morphine being synthetically made in a lab. Endogenous ligands are produced within the human body.

Question 17

What is a receptor?

Answer 17

the molecular target for the ligand. These are embedded in the membrane of cells. it is a biologically relevant molecular site with which a drug binds to produce a response.

Question 18

What is an agonist

Answer 18

a molecule that activates a receptor. It is a type of ligand.

Question 19

What is an antagonist

Answer 19

a molecule that blocks the response from the agonist-receptor binding. It is a type of ligand.

Question 20

What is meant by a drugs ‘target’

Answer 20

a molecule, usually a protein, that a drug intends to activate to produce a therapeutic effect.

Question 21

What does affinity mean

Answer 21

how well the ligand binds to a receptor. This is important to know as if it binds weakly then it might not efficiently activate, so it wont have the most effective action in the body.

Question 22

What is a steric interaction?

Answer 22

the physical shape of the drug needs to be compatible with the physical shape the receptor. This is one property that affects drug-receptor binding. However, electrostatic charges on the receptor and ligand are also important. They need to be oppositely charged to be compatible. A

Question 23

How are electrostatic charges important in the drug-receptor interaction

Answer 23

They need to be oppositely charged to be compatible.

Question 24

Describe what pharmacogenomics is

Answer 24

how a drug differs person to person due to genetics. The way an individual’s genetics attributes affect response to therapeutic drugs. so, we need to tailer the use of therapeutic agents more carefully to an individual’s genetic variations. For example, there could be genetic variation in the enzymes that process inactive drugs, in the proteins involved in cellular processes, and in the drug receptors involved.

Question 25

Describe what is meant by drug specificy

Answer 25

the measure of a receptors ability to respond to a single ligand. There are many responses to a drug by the body, and it is rare that drugs have only one. Non-specific interactions become more likely and significant with larger doses.

Question 26

What is meant by the absorption of a drug

Answer 26

the process by which the drug reaches the systemic circulation. It is affected by the route of administration and permeation (the ways the drug molecules can permeate tissues) drugs most be soluble and in a solution to be absorbed into the systemic circulation.

Question 27

Tell me a bit about the 2 rates of administration

Answer 27

there are 2 types of administration: enteral and parental. Enteral administration is where the drug is absorbed via the gut such as oral or rectal. Parental administration is where the drug is not absorbed via the gut such as an injection or topical cream.

Question 28

What are the 3 factors affecting distribution

Answer 28

there are 3 factors affecting distribution: protein binding, blood flow to the tissues, and membrane permeation.

Question 29

Briefly describe first pass metabolism

Answer 29

where some of the dose we swallow will never be absorbed as it is excreted straight away. It means some of the drug isn’t used by the body, and it mainly happens in the liver and the lungs. This is the problem with enteral administration routes.

Question 30

What does bioavailability mean? What affects a drugs bioavailability?

Answer 30

the proportion of active drug that reaches the systemic circulation and is free to bind to its target. Once the drug has been administered, the amount of drug available increases while it gets absorbed. Bioavailability of a drug is affected by the route of administration and formulation (eg if it has a coating). Intravenous has almost instant bioavailability, but oral drugs have slower availability as it has to dissolve in the stomach wall before it can get to the blood stream.

Question 31

What does metabolism mean? Are there phases izzie?

Answer 31

usually involves converting drugs into an inactive form in the liver. However, pro-drugs are actually activated by metabolism, such as codeine into morphine. There are 2 phases, which do not occur in any set order, and some drugs only need to go through one of the phases to be ready for excretion.

Question 32

What happens during phase 1 metabolism?

Answer 32

A range of chemical reactions take place to polarise (charge) the substance, increase its water solubility, and reduce its pharmacological activity. This usually produces toxic metabolites, but it can also activate prodrugs.

Question 33

What happens during phase 2 metabolism?

Answer 33

this converts toxins into soluble metabolites for excretion. The body does this by covalently bonding them to other molecules to ensure they are biologically inactive and water soluble.

Question 34

Tell me a bit about the excretion of a drug

Answer 34

most drugs are excreted by the kidneys in the renal system. Only unbound drugs can be processed via glomerular filtration as anything bound to a protein will remain in the blood. Biliary excretion is the main route.

Question 35

What is a drug half life? Why is it important to know!

Answer 35

the time taken to decreased plasma concentration of the drug to 50%. This is different in each drug depending on how quickly absorption, distribution, and metabolism happens. From knowing the half-life, you can work out when the patient will have removed all of the drug from their system, because most drugs have the same percentage of elimination per unit of time. For most drugs, by 5 half lives the plasma concentration of a drug is close or at 0%.

Question 36

What are the 3 names each drug has?

Answer 36

drugs have 3 different names. The chemical name describes chemical structure of the drug. Also, the generic name is the class of drug to which molecule belongs- so we can more easily refer to it. Finally, the proprietary name manufacturer’s name for the drug – the “trade name”

Question 37

What is the ideal drug?

Answer 37

one that has a desirable pharmacological effect with acceptable side effects, that reaches the target in the right concentration for good amount of time, and is completely removed from the body when it is no longer needed.

Question 38

What are enzyme inhibitors?

Answer 38

drugs that stop the enzyme from working normally

Question 39

What are false substrates?

Answer 39

drugs that bind to the enzyme and produce a false metabolite, which is a partially or completely dysfunctional in the biochemical pathway.

Question 40

What is a prodrug?

Answer 40

a biologically inactive compound which can be metabolized in the body to produce a drug. For example, codeine is metabolised by an enzyme to create morphine, which is the drug in its active form.

Question 41

Tell me what pharmacokinetics is

Answer 41

what the body does to the drug. This includes absorption, distribution, metabolism, and excretion. These processes determine the time of onset and the duration of the drug action in the body.

Question 42

Tell me what pharmacodynamics is

Answer 42

how the body affects the body. This includes the ligand-receptor interaction, affinity, drug binding, targets for drug action, and drug specificity. These all happen between the distribution and metabolism of the drug.

Question 43

What are the different types of injections?

Answer 43

intravascular, intramuscular, subcutaneous, dermal, depot.

Question 44

What are the 4 targets for drug action

Answer 44

receptors, ion channels, carrier molecules, and enzymes.

Question 45

Tell me in detail about the 4 targets for drug action

Answer 45

Firstly, when a drug targets a receptor within a membrane, it binds to it and there are a range of intracellular effects that take place to change the way the cell functions. Secondly, where a membrane has ion channels on it, drugs can interact with the channels by either blocking the pore or bind to the receptors on the ion channel to modulate its ability to move ions across. Next, carrier proteins facilitate transport across membranes through active transport and facilitated diffusion, and drugs can interact with them by inhibiting their function. Finally, enzymes get involved in biochemical processes in the body, and some drugs, such as aspirin can bind to them to stop them from working properly. The 3 types of drug that interact with enzymes are enzyme inhibitors, false substrates, and prodrugs.