Theophylline

Question 1

Theophylline

Answer 1

Xanthine bronchodilator

Question 2

IV aminophylline

Answer 2

Mixture of theophylline/ethylenediamine
20x more soluble
Irritant - cannot give IM

Question 3

Therapeutic range

Answer 3

Narrow T.I.
10-20 mg/L (55-110 mmol/L)
Take Cp 4-6 hours after dose.

Question 4

Cp increased

Answer 4

Heart failure
Hepatic impairment
Viral infections
Elderly
Enzyme inhibitor

Question 5

Cp decreased

Answer 5

Smokers
Alcohol
Enzyme inducers

Question 6

Signs of toxicity

Answer 6

“Fast and sick”
GI
CV
CNS
Electrolyte imbalances

Question 7

GI

Answer 7

• Vomiting
• Diarrhoea
• GI irritation

Question 8

CV

Answer 8

Tachycardia
Arrhythmias

Question 9

CNS

Answer 9

Convulsions
CNS stimulation
- Restlessness
- Agitation
- Dilated pupils

Question 10

Interactions - Increased risk of hypokalaemia

Answer 10

• Loop/thiazide diuretics
• Corticosteroids
• B2 agonists

Question 11

Interactions - increased risk of convulsions

Answer 11

• Ciprofloxacin
  Quinolones are enzymes inhibitors - they lower seizure threshold.
  SE of theophylline = convulsions
  Taken together = increased risk of SE

Question 12

Interactions - increased plasma concentration

Answer 12

Increased Cp = toxicity
- Verapamil/CCBs
- Cimetidine
- Phenytoin
- Fluconazole
- Macrolides

Question 13

Interactions - Reduced plasma concentration

Answer 13

Reduced Cp = concentration is subtherapeutic
- St. Johns wart
- Rifampicin