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LCRS - pharma > Pharmacokinetics > Flashcards

Flashcards in Pharmacokinetics Deck (30)
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1
Q

What are the 5 stages of a drugs journey through the body?

A

Absorption

Distribution

Metabolism

Excretion

Removal

2
Q

List some routes of drug administration.

A

Inhalation, ingestion, dermal, intravenous, subcutaneous, intraperitoneal, intramuscular.

3
Q

Why might different administration routes be more appropriate?

A

If you want a systemic or local effect.

Speed of action.

Time period within body.

4
Q

Give some examples of local effect drugs.

A

Salbutamol (ventolin)

Antacids

Betnovate (betamethasone)

5
Q

Give some examples of drugs with systemic effects.

A

Aspirin
Cannabis

Nicotine.

6
Q

What is the difference between enteral and parenteral.

A

Parenteral = outside the GI tract (i.e. not orally administered)

Enteral = via GI tract.

7
Q

What two ways to drug molecules move around the body?

A

Bulk flow transfer, i.e. in the blood stream.

Diffusional transfer = over short distances.

8
Q

What key characteristic must drugs have?

A

Have to be able to transverse both hydrophilic and lipophilic environments.

They travel in aqueous compartments (e.g. bloodstram, lymph, etc.)

Must cross lipophilic barriers (e.g. cell membranes).

9
Q

Name 4 ways drugs can cross lipid barriers?

A
  1. simple diffusion
  2. diffusion across aqeous pores.
  3. carrier mediated transport
  4. pinocytosis
10
Q

Outline the route of aspirin and the barriers it must cross.

A

Ingested. Cross stomach lining to blood. Cross capillary wall to extracellular fluid. Cross from extracellular fluid into organs.

11
Q

Which one of two characteristics will most drugs have? Why is this significant?

A

Weak acid or weak base.

Drugs exist in polar/non-polar (ionised/non-ionised) forms depending on pH.

12
Q

How do aspirin and morphine differ at phyisological pH?

A

Morphine = basic. Proton acceptor.

Aspirin = acidic. Proton donor.

13
Q

Give the Henderson-Hasselbalch equation for the dissaciation constand of weak acid and weak base.

A
14
Q

How can the proportion of ionised:unionised molecules of a species be calculated?

A
15
Q

What is ion trapping? Explain with aspirin as an example.

A

Localisation of a drug in certain body compartments. High ionisation of aspirin in the blood (pKa = 3.5) gives it difficulty crossing lipid membranes.

16
Q

Why does IV Sodium Bicarbonate increase aspirin excretion.

A

Basic conditions –> increased aspirin ionisation –> reduced ability to pass back into blood after kidney ultrafiltration.

17
Q

Give 4 factors that influence drug distribution.

A

Regional blood flow

Extracellular binding (Plasma-protein binding)

Capillary permeability (tissue alterations – renal, hepatic, brain/CNS, placental)

Localisation in tissues

18
Q

What parts of the body receive the greatest regional blood flow?

A

Liver 27%

Heart 4%

Brain 14%

KIdneys 22%

Muscles 20% (when exercising)

19
Q

What is the effect of plasma protein binding on drugs (e.g. 50-80% aspirin)? Why is this important?

A

It remains in the blood. Dose must be adjusted.

20
Q

Why is it difficult for drugs to cross the BBB

A

tightly controlled substance transport. Tight continuous capillaries: difficult for ionised substances to pass through.

21
Q

Why does adipose tissue pose a problem for lipid soluble drugs?

A

Despite low blood supply, lipophilic drugs contained within it.

22
Q

What are the two major routes of drug excretion?

A

Kidney (urine)

Liver (bile in stool)

23
Q

How are drug molecules too large for ultrafiltration moved into the kidney tubules?

A

Active secretion using transport proteins (lipophilic drugs can be reabsorbed)

24
Q

How do hepatocytes move large metabolites into the bile?

A

active transport of the water soluble conjugates they create.

25
Q

Outline enterohepatic cycling.

A

Gut bacteria break down watersoluble metabolite leading to reabsorption and drug persistence.

26
Q

List some minor ways drugs can be excreted.

A

Lungs, skin, gastrointestinal secretions, saliva, sweat, milk, genital secretions.

27
Q

Define bioavailability.

A

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

28
Q

Define the apparent volume of distribution?

A

The volume in which a drug appears to be distributed

  • an indicator of the pattern of distribution
29
Q

Define clearance.

A

the volume of blood (plasma) cleared of a drug (i.e. from which the drug is completely removed) in a unit time

30
Q
A