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Pharmacology > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

0
Q

Define drug.

A

Is a single chemical entity that may be

one of the constituents of a medicine.

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1
Q

Define medicine.

A

May contain one or more active constituents (drugs) together with additives to facilitate administration

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2
Q

Define therapeutic index.

A

Relationship between a drug’s therapeutic effect and adverse effects, a ‘margin of safety’

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3
Q

What are the processes involved in pharmokinetics?

A 
Absorption
Distribution
Metabolism
Excretion
Toxicity
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4
Q

What are gastrointestinal factors that influence absorption?

A

Oesophageal phase
pH of GI tract
Gastric motility
Presence of food and drink

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5
Q

Name administration routes for medication.

A

Enteral

  • oral
  • rectal

Parenteral (Avoid gut)

  • buccal
  • sublingual
  • topical
  • transdermal
  • lung etc
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6
Q

How many mls should be drunk to adsorb medication correctly!

A

200ml

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7
Q

Factors that affect drug distribution.

A

Blood flow in the tissue- sympathetic system which could activated in hypoxia, hypotension, hypo/hyperthermia, exercise
Binding to plasma protein
Cellular binding
Adipose store in the tissue

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8
Q

Define drug distribution.

A

Movement of a drug between the blood plasma and tissues continues until drug equilibrates

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9
Q

Consequences of drugs with a narrow therapeutic index with polyparmacy.

A

Competition in drug- protein binding means that increased amount of free lipid soluble drug as more than one molecule is attempting to bind to the protein.

This danger is increased with kidney issues

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10
Q

Define plasma binding.

A

Drug binding varies widely, for example warfarin is 98-99% bound to plasma albumin leaving only 1 - 2% free. Only the drug that is unbound or free is able to distribute to target tissues.

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11
Q

What occurs in phase one metabolism?

A

Takes a fat soluble substance and breaks it down to become a more water soluble molecules

Generally associated with small molecules

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12
Q

Drug metabolism.

A

Is the process by which the body breaks down and converts medication into active chemical substances.

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13
Q

What occurs in phase two metabolism?

A

Adds/conjugated on a water soluble molecule to make the whole complex more water soluble

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14
Q

Why are drugs metabolised?

A

Is crucial to drug exertion by making these molecules more water soluble.

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15
Q

What is cytochrome P450?

A

It is a phase 1 metabolic enzyme.

Responsible for metabolising >60% of all therapeutic drugs

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16
Q

What are ways of eliminating drugs?

A 
Redistribution
Liver metabolism
Renal excretion
Bile from liver
Lungs, faeces, saliva, sweat, breast milk, hair
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17
Q

What are the effects of metabolism?

A
  • renders the drug metabolites water soluble
  • produced metabolites are active in their own right
  • activates the active ingredient of the drug from a pro-drug molecules
    E.g. Enalapril (ACE inhibitors)
18
Q

Define pharmacokinetics.

A

Study of a drug’s alterations as it is absorbed
into, distributed through, metabolised in and
excreted from an organism

19
Q

What are the effects of protein binding?

A
  • Highly bound drugs require larger loading doses
  • Highly bound drugs have limited tissue distribution
  • Changes in available plasma protein, may have a profound effect on free drug availability
20
Q

Define first-past effect.

A

Process by which orally administered drugs
progress from the intestinal lumen to the
hepatic system before entering the general
circulation

21
Q

Define Bioavailability.

A

Degree to which a drug is
absorbed and reaches the
general circulation

22
Q

Define half-life

A

Time required to reduce the total amount

of a drug in a person’s body by 50%

23
Q

Where in the body is the main location for drug absorption?

A

The small intestine due to its large surface area

24
Q

What is the main aim of drug metabolism?

A

To make a drug more water-soluble.

25
Q

Define absorption.

A

explores the factors that influence drug entry into the body

26
Q

Define metabolism.

A

examines how a drug is converted to reduce its ability to teach its target

27
Q

Define excretion.

A

examines how a drug is removed from the body

28
Q

Define distribution.

A

examines the influences that affect how a drug reaches its target

29
Q

In which organ can we manipulate the pH?

A

Kidney

30
Q

What factors are affect the absorption of orally administered medications?

A 
GIT pH
Gastric motility
Splanchnic blood flow
GIT transit times
Fat solubility of the drug
31
Q

When is metabolism required in order to have a pharmacological effect?

A

When it acts on a pro-drug, otherwise it will not become active.

32
Q

Where does the majority of drug metabolism occur?

A

Liver

33
Q

Why is cytochrome P450 3A4 clinically important?

A

It is a phase 1 enzyme that metabolises 60% of all therapeutic substances.

34
Q

Name one of the main determinants of distribution.

A

Blood flow - the better the blood flow from the site of absorption, the better the distribution.

35
Q

What is the most important chemical characteristic of a drug in terms of pharmacokinetics?

A

Fat-solubility

36
Q

What is a P-glycoprotein?

A

Is a plasma membrane protein which acts as a localised drug transport mechanism it actively exports drugs out of the cell.

37
Q

What affect does P-glycoprotein have on fat-soluble drugs?

A

It reduces fat-soluble drug diffusion through barrier membranes.

38
Q

Define pharmacokinetics.

A

The study of the body’s interaction with a medication

40
Q

Why is packaging of tablets important?

A
  • Filler, to add bulk to the tablet e.g. lactose.
  • Substances that enhance drug disintegration, such as sodium bicarbonate that releases CO2 on contact with gastric acid.
  • Coated (wax or cellulose coating) tablets preserve acid unstable drugs from gastric acid and mask unpleasant taste.
  • Slow release preparations cover the active ingredient in a film that allows for slow release or the drug is bound in a matrix that allows slow leaching of active ingredient from the tablet
41
Q

What is the significance of GI transit time on drug absorption?

A

Shorter transit time means less amount of drug can be absorbed.

This can be affected by presence of food, also slower in women.

42
Q

How does GIT pH affect drug absorption?

A

The pH environment can change drug-membrane permeability by changing the charge (ionization) state of the drug molecule.

43
Q

How does pH change in the GIT?

A

Empty stomach pH 1.5-2.0
Full stomach pH 4-6
Duodenum 6
Rectum 7.5

Pharmacology (8 decks)

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