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Pharmacology > Block E > Flashcards

Block E Flashcards

1
Q

What is pharmacokinetics?

A

Refers to a drug’s journey within the body

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2
Q

ADME

What are the four stages of pharmacokinetics?

A
  • Absorption: Observes how a drug travels from the site of administration to site of action
  • Distribution: Observes the passage of a drug through the bloodstream to different tissue in the body
  • Metabolism: Observes the activity that breaks down a drug
  • Excretion: Observes the elimination of a drug from the body
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3
Q

What does pharmacodynamics refer to?

A

What the drug does to the bodY

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4
Q

What is used for measurement in pharmacokineticsa?

A

Blood/ Plasma concentrations- Easy to access

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5
Q

Suggest 3 sites of action for a drug.

A
  • Anatomical: compaartment drug has to reach
  • Cellular: The cell type the drug must reach
  • Molecular: The molecular target to which the drug must bind
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6
Q

Explain how Direct Oral Anti Coagulants work

A
  • Target the central plasma compartment
  • DOAC’s are small molecules that occupy the catalytic site of either FXa or thrombin, preventing their capacity to cleave and activate their substrates.
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7
Q

What receptor does carffeine target?

A

Adenosine receptors.

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8
Q

Outline the 3 adenosine receptors

A
  • Adenosine A2A receptor is mainly present in the brain, heart, lungs and spleen.
  • Adenosine A2B receptor has its major distribution in the large intestine and bladder.
  • Adenosine A3 receptor is present in the lungs, liver, brain, testis and heart.
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9
Q

What is the function of temozolomide?

A

Targets the DNA of brain tumour cells.

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10
Q

Through what systems are drugs distributed througout the body?

A

circulatory and lymphatic systems.

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11
Q

Suggest 3 Biological barriers which drugs must cross to reach their receptor.

A
  1. Gastrointestinal mucosa
  2. Blood brain barrier
  3. Placenta
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12
Q

What is a (simplistic) formula to work out drug concentration in the body?

A

Concentration= Dose/Volume

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13
Q

Suggest how different drugs may vary in their volume distribution

A
  • Large molecules will mainly stay in plasma- Very small VD
  • Hydrophilic/ Highly polar small molecule drugs will distribute into extraceullular fluid and have a relatively small VD.
  • Highly lipid soluble drugs distribute far more widely- Lerge VD
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14
Q

At what volume distributions will drugs be considered to be confined to various parts of the body.

A
  • VD-0.04 L/Kg are less thought to be confined to plasma
  • VD-0.06L/Kg are considered to be distributed to all tisseues in the body including fatty tissue
  • VD-10L Most of the drug is considered to be within the tissue with very little criculating in the plasma.
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15
Q

Name the body fluid compartments alongside the %volume they take up

A
  • Plasma-5%
  • Extracellular Fluid-15%
  • Intracellular Fluid-35%
  • Intracellular Fat-20%
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16
Q

What does partitioning of drugs refer to?

A

The fact that some drugs will accumulate in specific compartments of the body.

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17
Q

Give 3 examples of drug partitioning.

A
  1. Tetracycline accumulates in bones and teeth as they have a high affinity for calcium
  2. Amiodarone can accumulate in the liver and lung causing hepatitis and intersitial pulmonary fibrosis
  3. Chloroquine has a high affinity for melanin and can accumulate in the retina and lead to ocular toxicity
18
Q

Why can drugs partitioning into body fat cause issues?

A

Certain drugs e.g. benzodiazepines/ insecticides may accumulate in fat. Some drug doses are measured in mg/kg and must therefore be adjusted for obese patients.

19
Q

Why is grug efficacy reflected only by unbound drugs in the bloodstream?

A

Bound drugs may not passively diffues to extravascular/ tissue sites where pharmacologic drug effects occur

20
Q

What is drug elimination?

A

The loss of the drug from the body

21
Q

What are the main routes of drug elimination?

A
  • Excretion- kidneys
  • Metabolism- Liver
22
Q

What is the purpsoe of ther mass balance clinical study?

A

To understand how drugs are absorbed, metabilised and excreted after dosing

23
Q

Outline metabolism as a route of elimination for drugs

A

Most commonly occurs in the liver. Phase 1 rections introduce a reactive group into the molecule.
Phase 2 reactions allow conjucation to the molecule making it hydrophulic and suitable for elimination via the kidney.

24
Q

What does a pro drug molecule do?

A

Becomes converted into an active drug via metabolism

25
Q

Whare are CYP450?

A

A super family of enzymes.
Distinct but have some overlapping features
Typically involved in phase 1 oxidation, reduction and hydrolysis reaction in the liver

26
Q

How does liver disease affect CYP450

A

Reduction of activity in complex and undpredictable ways, therefore drugs metabolised in the liver should be used with caution.

27
Q

Why are CYP450 enzyme so important?

A

Responsible for the metabolism of ~70-80% of all drugs in clinical use

28
Q

Where is CYP3A4 most abundant?

A

In the liver where is ocmprises 15-20% of enzymes

29
Q

Suggest 2 common drug-drug interactions involving CYP3A4

A
  1. Clarithromycin/erythromycin and simvasrarin causing myopathy/rhabdomyolysis
  2. Diltiazem/veraspamil and prednisone causing immunosupression
30
Q

What does first pass metabolism refer to?

A

Drugs which pass through the liver and undergo metabolism before reaching the rest of the body

31
Q

what is the bioavailability of a drug?

A

The proportion of a drug which enters circulation when introduced into the body

32
Q

What is hepatic extraction ratio

A

The fraction of the drug entering the liver in the blood which is irreversibly removed during one pass through the liver

33
Q

How do you calculate the extraction ratio?

A

(Amount in- Amount out)/Amount in

34
Q

Name 3 important drugs metabolised in the intestine

A
  • Cyclosporine
  • Midazolam
  • Verapamil
35
Q

Give a brief outline fo renal excretion of drugs

A
  • Nearly all water+electrolytes are reabsorbed from renal tubes back to circulation
  • Large polar compounts (Most drug metabolites) cannot diffuest back into circulation unless a specific transport mechanism exists
36
Q

What is drug clearance?

A

The volume of plasma cleared of a drug over a specified time period.

37
Q

How do you calculate drug clearance?

A

Rate that drug is removed from plasma/Concentration of drug in plasma

38
Q

Suggest 3 factors affecting absorption

A
  1. Barriers to absorption:
    * IV-none
    * Oral-GI mucosa
    * Topical-Skin epithelium, Subcuatneous tissue
  2. Drug factors-affecting the rate and extend of absorption:
    * Molecular size/ lipid solubility/ chemical form
  3. Patient factors- affecting rate of absorption:
    * Surface area of absorptive surface
    * Blood flow to site of absorption
39
Q

What is an IND?

A

Investigational New Drug document- tells the story about the potential new substance

40
Q
A

Pharmacology (4 decks)

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