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Drug Action > Drug absorption and distribution > Flashcards

Drug absorption and distribution Flashcards

1
Q

What is pharmokinetics?

A

The study of the change in drug and metabolite concentrations in tissues and body fluids

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2
Q

What is a therapeutic window?

A

The range of concentrations that allow the drugs to reach their site of action below a toxic concentration

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3
Q

What is the therapeutic ratio?

A

Maximum non-toxic dose
Over
Minimum therapeutic dose

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4
Q

What is TD50?

A

The toxic dose of a drug for 50% of the population

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5
Q

What is ED50?

A

The minimum effective dose for 50% of the population

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6
Q

What is the relationship between therapeutic ration and drug safety?

A

The higher the therapeutic ratio, the safer the drug

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7
Q

What are the four parts to pharmokinetics?

A

Absorption
Distribution
Metabolism
Excretion

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8
Q

What is absorption?

A

Movement of the drug from point of administration to plasma

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9
Q

What is distribution?

A

From plasma to tissues and organs

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10
Q

What is metabolism?

A

Metabolism of drugs by enzymes in the body

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11
Q

What is excretion?

A

Excretion of drug or metabolite by the body

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12
Q

Why is ADME important?

A 
Drug development
Understanding toxicity
Establishing route of administration
Establishing drug dose
Understanding possible drug interactions
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13
Q

What is the definition of bioavailability?

A

Fraction of unchanged drug that reaches systemic circulation

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14
Q

What is the bioavailability of IV drugs?

A

100%

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15
Q

What is absorption dependent on?

A

Route of administration
Chemical nature of the compound
Formulation
Blood flow to site of delivery

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16
Q

What is formulation?

A

Tablet or liquid form etc

17
Q

What is the fastest route of administration?

A

Intravenous

18
Q

What is the slowest form of administration?

A

Orally

Rectally

19
Q

What are the six possible routes of administration?

A 
Intravenously
Sublingually
Orally
Rectally
Intramuscular
Subcutaneous
20
Q

What is a risk involved with intravenous drug administration?

A

Infection

21
Q

What is a side effect of intramuscular or subcutaneous drug administration?

A

Invasive and painful

Can cause local reactions

22
Q

What is a consequence of sublingual administration?

A

Only a small amount can be absorbed

23
Q

What must be considered when a drug is absorbed in the GI tract?

A

Its interactions with food
The rate of transit in the gut
pH sensitivity when passing through the stomach

24
Q

What can cross the cell membrane?

A

Very impermeable to charged molecules
Lipophilic molecules can cross the membrane
Particulates can cross by pinocytosis

25
Q

Where are weak acid and weak base drugs best absorbed?

A

In their uncharged states
In more alkaline conditions, more alkali drugs are absorbed
It is the same for acids

26
Q

Where do drugs tend to accumulate?

A

Where they are ionised as they then can’t cross any membranes

27
Q

What is first pass metabolism?

A 
Enteral drugs (oral or rectal) have to pass the liver
The metabolism of the drugs before they reach systemic circulation is known as first pass metabolism
28
Q

What is enterohepatic circulation?

A

Some drugs entering the gut are absorbed, enter the portal circulation, pass from liver to bile then back to the GI tract

29
Q

What drugs do not distribute?

A

Large drugs or those that bind to plasma proteins

30
Q

Define drug distribution

A

How drugs equilibrate within the body after entering the systemic circulation

31
Q

Where may drugs distribute?

A 
Not at all
Extracellular space
Total body water
Accumulate in cells
Distribute to fat
32
Q

What is the volume of distribution?

A

The volume of fluid required to contain the total amount of drug in the body at the same concentration as that present in the plasma

33
Q

How do you calculate volume of distribution?

A

Vd = D / Cp

D = amount of drug
Cp = plasma concentration
34
Q

What is the effect of binding to circulation proteins on drug action?

A 
e.g. albumin
Decreases initial free concentration
Slows distribution
Slows clearance
Prolongs duration of action
35
Q

What drugs bind to albumin?

A

Salicylates (eg aspirin)

Warfarin

Drug Action (19 decks)

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