Pharmacokinetics Flashcards

1
Q

Define T max

A

Time the drug takes to reach its max conc

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

Define C max

A

Max conc of drug in the plasma

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

Define bioavailability

A

Fraction of a dose which finds its way into a body compartment (usually circulation

IV = 100%

Other routes compare against IV)

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

How is bioavailability (F) calculated?

A

F = AUC oral / AUC IV

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

What factors affect bioavailability?

A

Drug formulation

Age

Food: lipid-soluble > water-soluble

Vomiting/malabsorption

First pass metabolism

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

Define first pass metabolism

A

Any metabolism occurring before the drug enters the systemic circulation

Occur in = gut lumen, gut wall, liver

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

Recognise the main routes of drug administration in to the body

A

Oral

IV

IM

PR

SL

Dermal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What key factors effect drug distribution?

A

Protein binding

Volume of distribution

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

Briefly outline the factors affecting drug-protein binding

A

Hypoalbuminaemia

Pregnancy

Renal failure

Displacement by other drugs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How can adding another drug affect protein binding?

A

Drug B may bind more highly = displaced drug A = higher [free drug A]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is volume of distribution?

A

measure of how widely a drug is distributed in body tissues

Vd = dose / [drug]t0

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

Describe CYPs

A

Genetically dependent

Role = oxidation, dealkylation, reduction, hydrolysis

Can be influenced by enzymes inducing/inhibiting drugs

CYP450 - mainly present in liver

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

Outline the factors affecting drug Metabolism

A

Race – CYP 2D6 absent in 7% caucasians

Age – reduced in older/children

Sex

Species

Clinical or physiological condition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the phases of drug metabolism?

A

Phase 1 = chemical changes, CYP450

Phase 2 = conjugation, increased solubility, allows excretion

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

What factors effect drug excretion

A

Age

Glomerular filtration

Passive tubular reabsorption

Active tubular secretion

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

Describe clearance

A

Ability of body to excrete drug

T ½ is inversely proportional to Cl

17
Q

How is drug half life calculated?

A

T1/2 = Vd / Cl

= proportionally equal to Vd

= inversely proportional to Cl

18
Q

Describe 1st order kinetics = Linear

A

Rate of elimination is proportional to drug level

Constant fraction of drug is eliminated in unit time

Half life can be determined

19
Q

Describe Zero order kinetics = Non-Linear Kinetics

A

Rate of elimination is a constant

Zero order drugs are more likely to result in toxicity = small dose changes may produce large increments in [plasma]

DRUG MONITORING ESSENTIAL

20
Q

Appreciate how Steady State therapeutic levels in plasma (CpSS) are reached

A

4-5 half lives required to reach steady state

21
Q

How are loading doses are employed to reach CpSS more rapidly

A

Used when pt require effective dose quickly

Very high first dose which sets the dose level appropriately

22
Q

How is digoxin toxicity treated?

A

Inject something that binds digoxin = inactive and gets eliminated