CPT S2 Pharmacokinetics II Flashcards Preview

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Flashcards in CPT S2 Pharmacokinetics II Deck (17)
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1
Q

Give examples of where drugs can act

A
Cell surface receptors
Nuclear receptors
Enzyme inhibitors
Ion channel blockers
Transport inhibitors
Signal transduction protein inhibitors
2
Q

Why is digoxin poisoning so common?

A

Predominantly excreted by the kidneys
Long half life
Old people have reduced/declining renal function
Old people take digoxin

3
Q

Why would you give a loading dose?

A

If you want a drug to reach a steady state quickly

If that drug has a long half life

4
Q

What occurs in a paracetamol overdose?

A

Paracetamol is no longer metabolised primarily by glucuronide or sulphate as the pathways are saturated. They undergo p450 oxidation to NAPQI, a hepatotoxin. This would be conjugated with glutathione to be eliminated, but this becomes depleted.

5
Q

How is paracetamol overdose treated?

A

Give N-acetylcysteine to replace glutathione and assist conjugation of NAPQI.

6
Q

Give some examples of mechanisms of action

A

Interaction with endogenous proteins (agonists, antagonists)
Disruption of structural proteins
Being enzymes (eg streptokinase)
Covalent lay linking macromolecules
Reacting with small molecules (antacids)
Binding free molecules or atoms (heavy metal poisoning drugs)

7
Q

Define potency

A

The dose required to produce a specific response

8
Q

Define efficacy

A

The level of response that occurs as a result of the drug binding to the target receptor.

9
Q

Explain drug selectivity

A

The more selective a drug is for its target, the less chance it will interact with different receptors, so is likely to have fewer undesirable side effects

10
Q

Give the equation for the therapeutic index

A

TI= toxic dose (TD50)/effective dose (ED50)

11
Q

Give some CYP450 inducers

A
Phenytoin
Carbamazepine 
Barbituates
Rifampicin
Alcohol
Suphonylureas&St John's Wort
12
Q

Give some CYP450 inhibitors

A
Omeprazole
Disulfiram
Erythromycin
Valproate
Isoniazid
Cimetidine and ciprofloxacin
Ethanol
Sulphonamides
13
Q

Give some common drug/food interactions

A

Grapefruit juice - inhibits several CYPs, decreasing clearance of many drugs including simvastatin and amiodarone.
Cranberry juice - inhibits a CYP, decreasing warfarin clearance and increasing risk of bleed.

14
Q

What chronic conditions can cause changes in drug clearance?

A

Renal disease
Hepatic disease
Cardiac disease

15
Q

How can renal disease affect clearance?

A

Falling GFR
Reduced clearance of renally excreted drugs
Disturbances in electrolytes may predispose to toxicity
Drug buildup may cause further kidney damage

16
Q

How can hepatic disease affect clearance?

A

Reduced clearance of hepatic metabolised drugs
Reduced CYP activity
Longer half lives
Toxicity

17
Q

How can cardiac disease cause reduced clearance?

A
Falling cardiac output
Excessive response to hypotensives
Reduced organ perfusion
Therefore reduced hepatic metabolism
And reduced renal elimination