Introduction To Pharmacology, Pharmacokinetics And Pharmacodynamics

Question 1

What is pharmacology?

Answer 1

Pharmacology is the study of medications or chemical compounds which interact with various living systems, from tiny molecules to cells to tissues to whole organisms in order to produce a certain effect.

Question 2

What are the phases of production of medication? What Happens in each phase?

Answer 2

Discovery phase
Preclinical phase
Clinical phase

1. The discovery phase- in this phase, a candidate compound is picked out as a possible therapeutic agent for a specific disease.
2. The preclinical phase- during which this compound is tested on cell cultures in animals like mice and rats, mainly to see if it causes any serious harm.
3. The clinical phase- the compound is tested first on healthy human volunteers to make sure it’s safe and finally on individuals suffering from that disease to find out if it’s indeed effective against this disease.
   If all of this goes well, then we’ve got a new medication.

Question 3

What are the 3 names a medication would have? Explain and give examples.

Answer 3

A medication will have at least three names

1. A chemical name- describing its chemical structure and used mostly in scientific studies, eg N-acetol-P-aminophenol.
2. A generic name- which is usually a shortened version of the chemical name, and is mostly used by health professionals such as paracetamol or acetaminophen.
3. Brand or trade names- given by the pharmaceutical companies that make the medication such as Panadol or Tylenol.

Question 4

What is the dose?

Answer 4

Every medication contains a precise amount of the active ingredient called the dose. So the dose is the precise amount of active ingredient present within a drug.

Question 5

What are the other components of a drug apart from the active ingredient? 3

Answer 5

The dose is often as little as five milligrams, and that’s less than a grain of sand. Since that’s too small to even handle. It’s usually combined with inactive substances like 1. fillers 2. binders, and 3. Lubricants that serve to fill out the medication and make it more convenient to use together.

Question 6

What are the chemical preparation form of drugs (4)? what are the methods of administration according to the chemical preparations (6)?

Answer 6

They get manufactured as a chemical preparation, like a pill, solutions, spray or ointment.

According to the form of the chemical preparation and the part of the body being treated, it can then be administered through various means or routes like

swallowed by the mouth (orally), 
Inhaled into the lungs, 
injected into a vein (intravenously), 
injected into a muscle (intramuscularly) 
sprayed into the nose (nasally),
applied on the skin (Cutaneously).

Question 7

What happens to the medication once administered?

Answer 7

Once administered the medication starts interacting with the body.

Question 8

The interactions of medication with the body can be broken down into?

Answer 8

The interaction of medications with the body can be broken down into:

1. Pharmacokinetics and 
2. Pharmacodynamics.

Question 9

What is pharmacokinetics?

Answer 9

Pharmacokinetics refers to the movement and modification of the medication inside the body. In other words, it’s what the body does to this medication.

Question 10

What are the stages of pharmacokinetics?

Answer 10

So once the medication gets administered, it

• first has to be absorbed into the circulation,
• then distributed to various tissues throughout the body,
• metabolized or broken down,
• and finally eliminated or excreted into the urine or feces.

You can remember this as ADME -absorption, distribution, metabolism, and elimination.

Question 11

What is pharmacodynamics?

Answer 11

Pharmacodynamics refers to the mechanisms and effects of medications within the body, or more simply, it’s what medications do to the body and how they do it.

Question 12

What is the difference between an ideal medication and the reality of most medications?

Answer 12

An ideal medication would produce a single beneficial or therapeutic effect for a certain disease state. In reality, though, most medications produce several unwanted effects called side effects, and these could be conditions like nausea or fatigue.

Question 13

Explain pharmacodynamics in basic terms

Answer 13

So once again, after the administration of a medication, it binds to receptors or specialized proteins located on the surface or inside a cell. This gives rise to a signal cascade, which ultimately results in some change in the cells function, like boosting the production of a particular type of protein or slowing down DNA replication.

Question 14

The factors that affect drug interaction with different individuals depend on? (5)

Answer 14

The way a medication interacts with the body (both pharmacokinetics and pharmacodynamics) varies widely from person to person.
It depends on a range of factors like: 
	- a person's genetic profile 
	- ethnicity
	- age
	- sex
	- the health of their liver or kidneys.

Question 15

State 6 ways in which medications can interact with each other.

Answer 15

Medications can also interact with one another as well. For example,

1. Competitive interactions
2. Synergistic effect
3. Antagonist effect
4. Permissive effect
5. Additive effect
6. Tachyphylactic interaction

Question 16

Explain competitive interaction of drugs.

Answer 16

In pharmacokinetics, it might be that the two medications are metabolized by the same enzymes, so they compete for the same enzyme sites.

Question 17

What is synergistic effect? explain with an example.

Answer 17

• In pharmacodynamics, the two medications might both increase the blood pressure producing a synergistic effect where the blood pressure goes up even higher than what you’d expect by simply adding the two medication effects together (effects of substance A and B together is greater than the sum of their individual effects

eg Clopidogrel with Aspirin- they both inhibit platelet aggregation (clot formation) so they can both increase the chance of excess bleeding. However, they can be used together in a stroke)

Question 18

What is an antagonistic effects in drug interactions?

Answer 18

A medication might work to increase blood pressure by simply opposing the effect of another medication, thereby having an antagonistic effect.

So an antagonistic effect is when one drug’s works by opposing the effect another drug.

Question 19

What is permissive effect? Give example and explain

Answer 19

Sometimes, the presence of one medication is required for the full effect of another (Presence of substance A is required for the full effect of substance B). This is a Permissive Effect.

Eg The effect Cortisol on Catecholamine responsiveness (they can both bind to alpha 1 receptors on arterioles, causing vasoconstriction). Cortisol actually upregulates alpha 1 receptors (enhances synthesis), and this allows norepinephrine to bind more Receptors.

Question 20

What is an additive effect? Give example and explain what they are and what they do.

Answer 20

Additive effect: effect of substance A and substance B together is equal to the sum of their individual effects.

Effectively aspirin and acetaminophen (These are both drugs that inhibit cyclooxygenase in the arachidonic acid pathway, they are anelgersics).

Question 21

What are tachyphylactic interactions?

Answer 21

Tachyphylactic interraction: tachy= fast, phylaxis= protection.

Question 22

What are three modern aspects or fields of pharmacology?

Answer 22

1. Pharmacogenetics, which combines pharmacology with genomics and uses genetic profiles to pair the right medication at the right dose to the right person.
2. Pharmacoepidemiology, which takes into account differences in medication responses between populations.
3. Pharmacoeconomics, which evaluates the costs and benefits of medications used in populations.

Question 23

What are receptors and what is their function?

Answer 23

In order to have an effect, most medications have to reach their target cells and bind to a receptor.

Receptors are specialized proteins both on the cell membrane and inside the cell, that can bind to a ligand and get triggered to alter their shape or activity. This gives rise to a signal cascade of intracellular molecules, which are the second messengers, which ultimately result in some change in the cells function.

Question 24

Where are intracellular receptors found? What do they bind (give examples)?

Answer 24

Intracellular receptors are typically found in the cytoplasm or nucleus of the cell and recognize small hydrophobic Ligands or water hating Ligands.

These include molecules like steroids, which can diffuse across the phospholipid membrane.

Question 25

What happens when intracellular receptors bind to the ligand?

Answer 25

Once bound to their ligand, the receptor-ligand complex attaches to specific DNA sequences that activate or inhibit specific genes.

Question 26

Where are cell surface receptors found and what do they bind?

Answer 26

On the cell membrane are cell surface receptors, which are embedded into the plasma membrane and bind to ligands too large or hydrophilic to pass through (hydrophilic meaning water loving).

Question 27

Cell surface receptors fall into three types based on their structure and properties, what are they?

Answer 27

Ligand gated in channels

G protein coupled receptors

Enzyme Coupled receptors

Question 28

How do ligand gated in channels work? What do they do?

Answer 28

Ligand gated ion channels form channels or pores that are generally closed, but then open up once they bind a specific ligand.

They allow ions like chloride, calcium, sodium, and potassium to passively flow into the cell, down their gradient and trigger the signaling pathway.

Question 29

What is another name for G protein coupled receptors

Answer 29

Seven-pass transmembrane receptors.

This means they’re really long proteins that have one end that sits outside the cell, and then the snake-like protein dips in and out of the cell membrane seven times and finally ends on the inside of the cell.

Question 30

Explain briefly how did G protein-coupled receptors work.

Answer 30

The ligand binds to the end sitting outside the cell, and then the end of the protein that’s within the cell activates guanine nucleotide binding proteins (or G proteins), which contain an alpha, beta and gamma subunit.

Normally the alpha subunit binds the guanosine diphosphate or a GDP molecule, and the G protein is inactive. However, when a ligand binds to the receptor, the G protein changes shape, causing the alpha subunit to release the GDP and allowing a guanosine triphosphate or GTP to bind. This causes the alpha subunit to detach and trigger other proteins in the signaling pathway.

Question 31

How many types of G proteins are there? Name them.

Answer 31

Broadly speaking, there are three types of G proteins, Gq, Gi and Gs.

Each type has its own kind of alpha subunit.

Question 32

What does the Gq protein do?

Answer 32

The Gq protein activates the enzyme phospholipase C, which cleaves a phospholipid called phosphatidylinostol 4,5- bisphosphate into inosital triphosphate and diacylglycerol.

Question 33

What does phospholipase C do once activated?

Answer 33

It cleaves phosphatidylinositol 4,5 bisphosphate into inositol triphosphate (IP3) and diacylglycerol (DAG)

Question 34

What do proteins Gs and Gi do?

Answer 34

protein Gs and Gi stimulate or inhibit respectively the enzyme adenylate cyclase. Which takes adenosine triphosphate or ATP and removes two phosphate molecules and transforms it into Cyclic Adenosine Monophosphate or cAMP.

Question 35

Name the 3 molecules produced by th G protein coupled receptors pathway, and What they proceed to do.

Answer 35

Inosital triphosphate, diacylglycerol and cAMP then go on to stimulate and inhibit different sets of enzymes and molecular pathways.

Question 36

Describe an enzyme Coupled receptor.

Answer 36

These are usually single pass transmembrane proteins, meaning that they only have one transmembrane segment. The extra cellular end of these receptors bind to ligands and their intracellular end has enzyme activity. The enzymatic domain is usually a protein kinase, which phosphorylates other molecules.

Question 37

How do enzyme Coupled receptors work?

Answer 37

When a ligand binds, it triggers a confirmational change in the enzymatic domain to form high affinity binding sites for the second messengers. These second messengers get phosphorylated by the tyrosine kinases before heading off to activate other proteins in the signal pathway.

Question 38

Explain medication specificity.

Answer 38

Every cell has a unique combination of many different types of receptors, and in theory, each medication is specific to a particular receptor, just like each key fits into and opens a particular lock.

This is described as a medication’s specificity.

In reality, though, no drug is a hundred percent specific, because they could also bind to other receptors that are similar to its intended target, which is why all medications cause side effects.

Question 39

Why do all medications cause side effects?

Answer 39

In reality, no drug is a hundred percent specific, because they could also bind to other receptors that are similar to its intended target, which is why all medications cause side effects.

Question 40

What are the two main (plus one more) principles that rule the way a medication and its receptor interacts?

Answer 40

Affinity

Intrinsic Activity

(Efficacy)

Question 41

Drug-Receptor interactions. What is affinity? What mainly determines it?

Answer 41

Affinity- The ability of a drug to bind to its receptor, how well drug and receptor recognize one another, how strongly a medication binds to its receptor. This is mainly determined by the strength of the chemical bond between the two.

Question 42

What is potency and what is its relationship with affinity?

Answer 42

Potency is the amount of medication needed to elicit an effect. So medications with high affinity can produce an effect at a lower dose.

The higher the affinity, the higher the potency. (If the affinity is high, we’d need less, and very potent drug means that less brings high effect)

A potent drug has a high affinity and can produce effects even at low doses.

Question 43

What is Intrinsic Activity?

Answer 43

Intrinsic Activity us the ability of a drug to activate it’s receptor when bound.

After the medication binds to its receptor, it must also be able to activate that receptor, this ability is known as intrinsic activity.

Ultimately, the intensity of response to the medication (Intensity of medication’s effect) depends on both the number of receptors bound to the medication as well as its intrinsic activity.

Question 44

What does intensity of the response to a medication depend on?

Answer 44

Ultimately, the intensity of response to the medication (Intensity of medication’s effect) depends on both the number of receptors bound to the medication as well as its intrinsic activity.

Question 45

What is efficacy?

Answer 45

Efficacy- The maximal effect the medication can produce is called the efficacy. It is equal to the Emax value.