Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

EyeNotes Chapters > PHARMACOLOGY - Pharmacokinetics and pharmacodynamics > Flashcards

PHARMACOLOGY - Pharmacokinetics and pharmacodynamics Flashcards

1
Q

What factors affect diffusion coefficient? (3)

A
  1. Lipid solubility
  2. Ionization
  3. Molecular size
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is Fick’s Law?

A

rate of diffusion = diffusion coefficient x concentration gradient / membrane thickness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens to drug absorption with increased blink rate?

A

Reduces by increasing clearance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What effect does acidity/alkaninity have on a drug?

A
  1. More unionised and so more lipid soluble to increase corneal absorption
  2. Causes irritation/lacrimation –> drug clearance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does Phase 1 drug metabolism involve?

A

oxidation reactions (carried out by cytochrome P450)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What do Phase 2 drug metabolism involve?

A

conjugation reactions (addition of glucuronate, glutamine and acetate groups) which makes molecules more water soluble for excretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the most important factors on rate and extent of ocular absorption (5)

A

PRE-corneal factors
1. Tear volume (7-30ul)
2. Tear turnover time (-.5-2.2ul/min)
3. Blink rate (15-min)

all these factors limit drug time in conjunctival sac to 3-5 minutes on average

  1. Corneal thickness
  2. Conjunctival:corneal surface area (17:1)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the greatest barrier in the cornea for ocular drug penetration?

What route do lipophilic drugs go by?
What route do hydrophilic drugs go by?

A

Corneal epithelium (lipophilic layer)

Lipophilic drugs –> intracellular route
Hydrophilic drugs –> paracellular route

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What compounds are most likely to penetrate the cornea to reach the anterior chamber (ie biphasic - both hydrophilic and hydrophobic) (3)

A
  1. Acetate (most)
  2. Alcohol
  3. Phosphate (least)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the difference between lipid soluble and water soluble drugs? (3)

A
  1. Lipid soluble enter BBB so have more CNS effects
  2. Water soluble are easier to clear
  3. Hepatic drug metabolism converts lipid soluble drug into a water soluble drug
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which drugs accumulate in the cornea? (2)

A
  1. NSAIDs
  2. Pilocarpine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is bioavailability?

A

The amount of oral dose that reaches systemic circulation and is available to the site of action

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the factors affecting first-pass metabolism? (5)

A
  1. Gut motility.
  2. Intestinal pH, bile salts
  3. Intestinal blood flow
  4. Intestinal microflora
  5. Enterohepatic circulation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why do ocular drugs have higher bioavailability?

A

They are absorbed by the nasal mucosa and so bypass first pass metabolism.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Whats the difference between first order and zero order drug kinetics?

A

First order: proportional linear increase in rate of drug consumption with concentration of drug

Zero order: saturation occurs at high drug concentrations (eg when liver enzymes are at full capacity)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which type of drugs are able to pass the blood-retinal barrier?

A

Lipophilic (lipid soluble) drugs

17
Q

What is the EC50?

A

The amount of ligand required to achieve 50% of full capacity binding

(relationship between a ligand and its receptor)

18
Q

What is a partial agonist?

A

Has both agonist and antagonist qualities - at high concentrations, exerts antagonist activity by blocking TRUE agonists

19
Q

Where is the most common site for topical administration?

A

Inferior fornix

20
Q

What is the conjunctival sac capacity?
What is the average amount of eyedrop?
Where is the drop lost to?

A
  1. 15-30mL
  2. 50-100mL
  3. Most is lost via overspill and tear turnover
21
Q

Which substances can increase viscosity which in turn increases time of drug in the conjunctiva?

A

Polyvinyl alcohol
Hydroxypropylcellulose

22
Q

What layer can preservatives be toxic to?

A

Precorneal tear film and epithelium

23
Q

What are the main properties of preservative benzalkonium chloride? (3)

A
  1. Toxic to cornea
  2. Bactericidal by rupturing cell walls
  3. Most effective at pH 8
24
Q

How is VEGF upregulated?

A

Hypoxic state –> increase in hypoxic inducible factor –> release of VEGF –> breaks down inner blood retinal barrier and increases capillary permeability

25
Q

What is the mechanism of action of anti-VEGFs?

A

Bind to soluble VEGF and block its activity by preventing its binding to VEGF receptors (VEGF-1 and VEGF-2)

26
Q

What type of receptors are VEGF-1 and VEGF-2?

A

Tyrosine kinase receptors

27
Q

What is the mechanism of action of Ranibizumab (Lucentis)

A

Monoclonal recombinant human Fab against VEGF - targets all VEGF-A receptors and its products.

Lacks an Fc region and so is very small and easily penetrates the retina

28
Q

What is the mechanism of action of Bevacizumab?

A

recombinant humanized antibody but is full sized and has two antigen binding domains rather than one - lasts longer

29
Q

What is the mechanism of action of Aflibicept?

A

A recombinant fusion protein which acts as a VEGF receptor decoy - it traps all VEGF with greater affinity so prevents binding to other VEGF receptors.

30
Q

Which ocular surface disease is linked to these tear film deficiencies:
1. Aqueous deficiency
2. Mucin deficiency
3. Lipid deficiency

A
  1. Aqueous - Sjogren’s syndrome
  2. Mucin - cicatriacal conjunctival disease and hyovitaminosis A
  3. Lipid - chronic meibomian gland inflammation
31
Q

What do mucolytics do? (acetylcisteine)

A

dissolves mucus threads that develop in keratoconjunctivitis sicca (does not affect corneal wetting)

32
Q

What is the difference between pharmacogenetics and pharmacogenomics?

A

genetics - study of how genetic variation influences drug efficacy and toxicity but focus in on single genes

Genomics - study of how individuals genome affects drug response

33
Q

Whats the difference between pharmacokinetics and pharmacodynamics?

A

dynamics: study of mechanism of action, biochemical and physiological effects on biological system (DOWNSTREAM)

pharmacokinetics - how the drug is absorbed, distributed, metabolised and excreted

34
Q

Which factors can increase bioavailability in the cornea? (4)

A
  1. increased lipid solubility
  2. mild alkaninity of topical medication
  3. high viscosity, increasing drug retention
  4. isotonicity of topical medication
35
Q

Whats the difference between phase I and phase II metabolism?

A

Phase I - oxidative reactions by cytochrome p450

Phase II - conjugation reactions (addition of groups) to make molecules more water soluble for excretion

EyeNotes Chapters (83 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions