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3.24 > Lecture 15: Concentration-time profiles and therapeutic drug monitoring of theophylline > Flashcards

Lecture 15: Concentration-time profiles and therapeutic drug monitoring of theophylline Flashcards

1
Q

What is the oral dose of theophylline for?

A

Add on therapy for persistent symptoms of COPD

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2
Q

What is the IV dose of theophylline given as?

A

Aminophylline

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3
Q

What is aminophylline used for?

A

Severe acute asthma and for acute exacerbations of COPD

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4
Q

What are the advanatges of theophylline?

A

Cheap and widely available

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5
Q

What was theophylline originally developed as?

A

A diuretic

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6
Q

What are the pharmacological properties of theophylline?

A
  • Inhibits PDE
  • Antagonises adenosine receptors
  • Inhibits proinflammatory transcription factor nuclear factor-kB
  • Restores histone deacetylase 2
  • Increases apoptosis of inflammatory neutrophils and T cells
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7
Q

What is the result of PDE3 inhibition?

A
  • Relaxes airway smooth muscle
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8
Q

What is the result of PDE4 inhibition?

A

Reduces mediator release from alveolar macrophages

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9
Q

What may be responsible for severe toxicity?

A

Adenosine A1 receptor blockage

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10
Q

What causes bronchoconstriction via histamine and leucotriene release?

A

Adenosine

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11
Q

What concentration of theophylline hasa little effect on bronchodilation?

A

<10 mg/L

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12
Q

What concentrations of theophylline have an increased effect on bronchodilation?

A

10-25 mg/L

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13
Q

What concentrations of theophylline have no additional benefit on bronchodilation?

A

> 25 mg/L

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14
Q

What effect does theophylline have on COPD patients and at what concentration?

A

reduces proportion of neutrophils in sputum
at 5-10 mg/L

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15
Q

What effect does theophylline have on asthma patients?

A

reduces eosinophil response to allergens, neutrophil influx, reduces CD4+, CD8+ neutrophils in airways

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16
Q

What is the steroid sparing effect of theophylline and at what dose?

A

increases sensitivity of COPD to the anti-inflammatory effects of inhaled corticosteroids at 1-5mg/ L

17
Q

At what concentrations dose theophylline become toxic?

A

> 15 mg/L

18
Q

What are the effects of theophylline at concnetrations >20 mg/L?

A
  • nausea
  • vomiting
  • headache
  • tachycardia
  • tremor
  • diuresis
19
Q

What are the effects of theophylline at concentrations >40 mg/L?

A
  • seizures (may cause rhabdomyolysis)
  • cardiac arrhythmias
  • (hypokalaemia) may occur at lower concentrations in chronic overdose
20
Q

What are the target concentration of theophylline for bronchodilation?

A

10-20 mg/L

21
Q

What are the target concentration of theophylline for anti-inflammatory and steroid sparing effect?

A

5-15 mg/L

22
Q

What is the bioavailability of theophylline?

A

100%

23
Q

Why are modified release oral formulations of theophylline used?

A

to reduce need for multiple daily doses

24
Q

What is the distribution of theophylline?

A

0.48 L/kg

25
Q

How is theophylline cleared?

A

By hepatic metabolism - by CYP1A2

26
Q

What increases the clearance of theophylline?

A
  • Smoking (including passive)
  • Cystic fibrosis
  • Enzyme inducers
27
Q

What decreases the clearance of theophylline?

A
  • Heart failure
  • Acute viral illness
  • Cirrhosis
  • Severe COPD
  • Enzyme Inhibitors
28
Q

What drugs increase the clearance of theophylline?

A
  • Rifampicin
  • Carbamazepine
  • Phenytoin
  • St johns wart
29
Q

What drugs decrease the clearance of theophylline?

A
  • clarithromycin
  • erythromycin
  • ciprofloxacin
  • fluvoxamine
  • diltiazem
30
Q

What drugs interact with theophylline to cause hypokalaemis?

A
  • Diuretics
  • Beta 2 agonist
31
Q

What drugs interact with theophylline to cause seizures?

A
  • Ketamine
  • Quinolone antibiotics
32
Q

What is aminophylline?

A

Stable mixture of two molecules of theophylline and one molecule of ethylene diamine

33
Q

What is the purpose of the salt in aminophylline?

A

Improves solubility - makes it easier to be given IV

34
Q

What is the intravenous form of theophylline?

A

Aminophylline

35
Q

What is intravenous aminophylline indicated for?

A

Severe acute asthma

36
Q

What is the dose of IV aminophylline for severe acute asthma?

A

5mg/kg by slow IV injection followed bt 500-700 micrograms/kg/h by IV infusion

37
Q

Why does the loading dose of aminophylline need to be given slowly?

A

To avoid severe risk of toxicity particularly arrhythmias

38
Q

How is a loading dose calculated?

A

Loading dose (IV) (mg) = Target concentration (mg/L) x V (L)/s

3.24 (28 decks)

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