Poisioning Flashcards

1
Q

What is the apparent volume of distribution of digoxin?

A

Over 200L - large

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2
Q

What is the half life of digoxin?

A

40 hours

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3
Q

How long would it take for digoxin to reach a steady state?

A

Over a week

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4
Q

What is the consequence of digoxin taking over a week to reach a steady state?

A

You need loading doses to achieve a rapid therapeutic effect

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5
Q

Why is it important to use a loading dose with digoxin?

A

As you need to achieve satisfactory control of atrial fibrillation quickly

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6
Q

How does the loading dose of digoxin compare to the maintenance dose?

A

It is 4-8x as much

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7
Q

Other than taking a long time to reach a steady state, what is the other consequence of the long half life of digoxin?

A

It takes a long time to eliminate

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8
Q

How long does it take to reduce the concentration of digoxin by 50% in a patient with normal GFR?

A

40 hours

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9
Q

What happens to the clearance of digoxin in a patient with renal failure?

A

The clearance is reduced and so the half life will be increased

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10
Q

What is the result of the increase in half life of digoxin in a patient with renal failure?

A

It takes longer for the concentration of drug to return to therapeutic levels if the patient becomes digitoxic

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11
Q

What is digoxin predominantly excreted by?

A

Kidneys

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12
Q

What needs to be done to maintanance doses of digoxin in renal failure?

A

Needs reducing, as the renal failure leads to reduced clearance

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13
Q

What happens to loading doses of digoxin in renal failure?

A

They remain much the same, unless renal failure is very severe

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14
Q

What kind of kinetics does digoxin show?

A

First order kinetics

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15
Q

What will the clinical effectiveness of digoxin after it is stopped depend on?

A
  • Therapeutic window
  • Minimal effective plasma drug concentration
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16
Q

What are the symptoms of a digitoxic patient?

A
  • Bradycardia
  • Xanthopsia
  • Vomiting
17
Q

What needs to be done when a patient presents as digitoxic?

A

Need to give a drug that binds digoxin to eliminate it

18
Q

What is paracetamol metabolised into at normal doses?

A
  • 60% is converted to paracetamol glucuronide
  • 30% is converted to paracetamol sulfate
  • 10% is ungergoes P460 oxidation to NAPQI
19
Q

What happens to the NAPQI produced as a result of paracetamol metabolism?

A

It is conjugated with glutathione to inactive metabolites

20
Q

What inactive metabolites are formed when NAPQI is conjugated with glutathione?

A

Cysteine and mercapturic acid

21
Q

What happens in substantial paracetamol overdose?

A

The conjugation of NAPQI is saturated, leading to increased toxic levels of NAPQI

22
Q

What is the treatment for paracetamol overdose?

A

To replace glutathione, e.g. with N-acetylcysteine