Pharmacokinetics and drug metabolism Flashcards

1
Q

What are the 4 stages of a drugs journey through the body?

A

Absorption
Distribution
Metabolism
Excretion

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2
Q

What are the possible ways of administering drugs?

A
Ingestion
Dermal
Intramuscular
Subcutaneous
Intraperitoneal
Intravenous
Inhalation
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3
Q

What is a systemic drug and give a common example?

A

Affects entire organism and aspirin

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4
Q

What is a local drug and give a common example?

A

Restricted to one area of the organism and salbutamol

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5
Q

What is an enteral drug and give a common example?

A

Gastro-intestinal administration

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6
Q

What are the two ways that drugs move around the body?

A

Bulk flow transfer e.g. bloodstream

Diffusional transfer e.g. molecule by molecule over short distance

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7
Q

What are the compartments and barriers that drugs have to traverse?

A
Compartments= aqueous e.g. blood, lymph, extracellular fluid and intracellular fluid
Barriers= Lipid e.g. cell membranes (epithelium/endothelium)
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8
Q

How can drugs cross these barriers?

A

Diffusing through lipid
Carrier molecules
Diffusing through aqueous pores in lipid
Pinocytosis

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9
Q

How do most drugs exist?

A

Weak acids (ionised) or weak bases (non-ionised)

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10
Q

What is the difference between ionised and non-ionised drugs?

A

Non ionised/non polar can freely dissolve in non-polar substances e.g. penetrate lipid membranes freely

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11
Q

What factors affect drug distribution?

A

Regional blood flow
Extracellular binding (plasma proteins)
Capillary permeability
Localisation in tissues

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12
Q

How does metabolism affect blood flow?

A

Higher metabolically active tissues lead to denser capillary networks

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13
Q

What percentage of acidic drugs are plasma protein bound?

A

50-80%

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14
Q

What are the two major routes of drug excretion?

A

Kidney- responsible for elimination of most drugs

Liver- Some drugs are concentrated in bile

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15
Q

What happens to drug-protein complexes when they reach the glomerulus?

A

They are not filtered

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16
Q

What happens at the proximal tubule in terms of excretion?

A

There is active secretion of acids and bases

17
Q

What happens at the proximal and distal tubules in terms of reabsorption?

A

Lipid soluble drugs are reabsorbed

18
Q

How does treatment with intravenous sodium bicarbonate increase aspirin excretion?

A

It increases urine pH which ionises the aspirin making it less lipid soluble and less reabsorbed from the tubule increasing its rate of excretion

19
Q

Apart from the two main routes, what other routes of excretion are there?

A
Lungs
Skin
Gastrointestinal secretions
Saliva
Sweat
Milk
Genital secretions
20
Q

What is bioavailability?

A

Proportion of administered drug that is available within the body to exert its pharmacological effect

21
Q

What is the apparent volume of distribution?

A

The volume in which a drug appears to be distributed- an indicator of the pattern of distribution

22
Q

What is biological half life?

A

The time taken for the concentration of the drug in the blood to fall to half its original value

23
Q

What is clearance?

A

Blood clearance is the volume of blood cleared of a drug in a unit time

24
Q

What is first order kinetics?

A

The rate of elimination of a drug where the amount of drug decreases at a rate that is proportional to the concentration of drug remaining in the body

25
Q

What is the volume of distribution?

A

Dose divided by the initial concentration of the drug in the plasma

26
Q

What is zero order kinetics?

A

A constant amount of drug is removed per unit time (something is saturating the rate of removal, usually an enzyme)

27
Q

What common sort of drug follows zero order kinetics?

A

Alcohol

28
Q

What kinetics do most drugs follow?

A

First order