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Introduction to Pharmacology > Basic Principles of Pharmacology > Flashcards

Basic Principles of Pharmacology Flashcards

1
Q

What is a drug?

A

A molecule with a known structure that results in a biological effect but is not a nutrient or dietary supplement

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2
Q

What is a medicine?

A

A drug or combination of drugs that has a therapeutic effect on the body

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3
Q

How are drugs classified?

A

Structure
Mode of action
Therapeutic use

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4
Q

How are drugs named?

A

Chemical name
Generic name
Trade name

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5
Q

What are pharmacokinetics?

A

What the body does to the drug

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6
Q

What are pharmacodynamics?

A

What the drug does to the body

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7
Q

What are the four stages of a drug in the body?

A

Absorption
Delivery
Metabolism
Excretion

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8
Q

Which is the only route of administration that offers 100% bioavailability?

A

Intravenous infusion

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9
Q

What is bioavailability?

A

How much of the drug makes its way into the systemic circulation

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10
Q

What are enteral routes of administration?

A

Any route that involves the gastrointestinal tract

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11
Q

What are parenteral routes of administration?

A

Any route that does not involve the gastrointestinal tract

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12
Q

Why is oral best for administration?

A

Cheap
Easy to dose
Can be done without medical professionals present
Rapid onset

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13
Q

What must happen before an oral drug can be absorbed?

A

It must be dissolved

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14
Q

What affect does the dissolution rate have on the drug’s action and how can this be affected?

A

It is the limiting factor in absorption rate and can be altered by changing the surface area or adding a coating to the tablet to prevent/quicken dissolution

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15
Q

Where are oral drugs absorbed?

A

Anywhere along the GI tract but usually across the small intestine

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16
Q

Why is oral routes the most complex for absorption?

A

The body is designed to prevent absorption of foreign molecules

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17
Q

What barriers does the body have against absorption of orally taken drugs?

A

Gastric acid
Digestive enzymes
Survive and coexist with food
Cope with gut microbiota

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18
Q

Explain how the gut microbiota can be used in our favour for drug action

A

The microbiome can transform the prodrug into it’s active form. This is useful particularly in the colon to make sure the drug gets to the target site

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19
Q

How does absorption usually occur?

A

Transcellular passive diffusion

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20
Q

Why are most drugs weak acids or bases?

A

The drug must be lipophilic to diffuce across the gut epithelium but must dissolve to be able to be absorbed. Weak acids and bases can dissociate into both an ionised form and an unionised form so can both be dissolved in water and diffused across the membrane

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21
Q

What are the role of P-glycoproteins

A

They are a ATP powered drug efflux pump and reduce bioavailability by pumping drugs back out of the epithelial cells

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22
Q

Why can L-Dopa pass through the GI tract by a transporter?

A

It has a very similar structure to tyrosine

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23
Q

Describe the first pass effect

A

The venous drainage from the GI tract goes directly to the liver via the hepatic portal vein. The liver is the main site of metabolism so any drug must survive this stage in order to be truly bioavailable

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24
Q

Describe sublingual administration

A

The drug is placed under the tongue and is absorbed straight into systemic circulation without passing through the liver, however there is a much smaller surface area for absorption

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25
Q

Describe rectal administration

A

The drug is inserted into the GI tract via the anus. Useful when the oral route is compromised due to vomiting or when the drug needs to be used a lot e.g. chronic pain relief and NSAIDs

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26
Q

Describe intravenous administration

A

The drug is placed directly into the systemic circulation to allow rapid onset

27
Q

Describe intramuscular/subcutaneous administration

A

The drug is injected under the skin or into the muscle and creates a depot of drug that can be slowly released into the systemic circulation

28
Q

Describe inhalation administration

A

The drug enters the pulmonary circulation via the lungs due to the lung parenchyma permeability and low metabolism

29
Q

Describe intranasal administration

A

The drug enters into the systemic circulation via the jugular vein

30
Q

Describe topical administration

A

The drug is applied directly to the site of action for a local affect and generally won’t be absorbed by the body

31
Q

Describe transdermal administration

A

A patch containing the drug creates and external depot of the drug to be slowly absorbed by the skin

32
Q

What is drug distribution?

A

The reversible movement of drugs from systemic circulation into cells & interstitium

33
Q

How do drug enter the tissues from capillaries?

A

Paracellular passive diffusion

34
Q

Why is drug distribution not uniform?

A

Perfusion rates vary between different organs

35
Q

What determines distribution of lipophilic drugs?

A

Perfusion rates

36
Q

How does the anaesthetic thiopental stop working?

A

The drug diffuses back across the blood brain barrier to the periphery where it has no effect

37
Q

How can the blood brain barrier be used to our advantage?

A

It is very impermeable so we can use this to prevent drugs that we don’t want in the brain from getting in

38
Q

Describe why L-Dopa is used to treat Parkinson’s but not dopamine

A

Dopamine cannot cross the blood brain barrier but L-dopa can

39
Q

Why is L-Dopa taken with carbidopa?

A

Carbidopa inhibits dopa decarboxylase but cannot cross the blood brain barrier. This means that L-Dopa will be converted to dopamine in the brain where it’s needed but not in the periphery where it will cause damage

40
Q

Where are P-glycoproteins present?

A

GI epithelium
Blood brain barrier
Placenta

41
Q

What can affect bioavailability from the systemic circulation

A

The drug’s affinity with plasma proteins

42
Q

Describe the drug-drug interaction between aspirin and warfarin

A

Warfarin binds readily to albumin however aspirin has a higher affinity so displaces the warfarin and will increase the bioavailability

43
Q

What is drug sequestration?

A

The accumulation of drugs in a tissue to the point at which the concentration in the tissues becomes higher.

44
Q

What is drug metabolism?

A

The chemical modification of xenobiotics

45
Q

What is the main site of metabolism?

A

The liver

46
Q

What is phase 1 metabolism?

A

Oxidation, reduction or hydrolysis by cytochrome P450

47
Q

What is phase 2 metabolism?

A

Conjugation

48
Q

Describe the metabolism of paracetamol

A

Phase 1 - Oxidation to NAPQI

Phase 2 - Conjugation with GSH

49
Q

Describe the metabolism of tamoxifen

A

Metabolised to endoxifen by reduction. Endoxifen is the active drug which binds to oestrogen receptors

50
Q

Describe the metabolism of aspirin

A

Hydrolysed into salicylic acid and acetic acid

51
Q

How can we alter a drug’s metabolism?

A

Adding different bonds that are metabolised faster or slower

52
Q

What are three types of phase 2 metabolism?

A

Glucuronidation, sulphation and acetylation

53
Q

Describe enzyme induction

A

The drug induces cytochrome P450 which reduces availability of other drugs

54
Q

Describe enzyme inhibition

A

Metabolic enzymes are inhibited by the drug which increases availability of other drugs

55
Q

What can affect drug metabolism?

A

Age

Illness

56
Q

What routes can drugs be excreted by?

A

Faeces, lungs, saliva, sweat, tears, breastmilk, urine

57
Q

How is renal excretion calculated?

A

(filtration + secretion) - reabsorption

58
Q

What drugs can pass through the Bowman’s capsule?

A

Any drug not bound to plasma proteins

59
Q

What affect does glucuronidation have on renal secretion?

A

It make the drug a substrate of organic anion transporters in the PCT so they can be taken into the tubule

60
Q

What affect does probenecid have when taking drugs that are naturally substrates of OATs

A

Probenecid blocks OATs to prevent transport

61
Q

How can reabsorption be manipulated?

A

Altering the pH of the urine - changes the position of the dissociation equilbrium so more/less of the drug is in the charged form which is more easily excreted

62
Q

What affect does SGLT2 inhibition have?

A

Prevents glucose reabsorption independently of beta cell function and insulin

63
Q

Describe enterohepatic cycling

A

The drug is glucuronidised, then enters the bile caniculi and entered back into the GI tract. Some will then have their glucuronic group removed so it is reabsorbed into the systemic circulation

Introduction to Pharmacology (12 decks)

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