Theophylline

Question 1

Therapeutic Range:

Answer 1

Therapeutic Range: 10 to 20mg/L (55 to 110micromol/L)
(although a plasma theophylline concentration of 5 to 15mg/L may still be effective)
Loading doses may be required

Question 2

Monitoring

Answer 2

Serum potassium, plasma theophylline concentartion

Question 3

Major Route of Elimination

Answer 3

Hepatic metabolism

Question 4

Warning Signs

Answer 4

• Toxicity e.g. vomiting (may be intractable), agitation, restlessness, dilated pupils, sinus
tachycardia, hyperglycaemia, severe hypokalaemia may develop rapidly, haematemesis,
convulsions, cardiac arrhythmias
• Symptoms of uncontrolled asthma (cough, wheeze, tight chest)
• Frequent courses of antibiotics and/or oral corticosteroids

Question 5

Actions Required

Answer 5

• Advise patient to report immediately to a doctor if any warning signs occur
• Inform the patient of potential interactions with theophylline and the need to check with a
pharmacist or doctor before taking any new medication (including OTC, prescribed or herbal
medicines)
• Advise patient to inform their GP before stopping or starting smoking
• Emphasise the importance of maintaining on the same brand of medicine and recommend
that the patient always checks when collecting their medicine from a pharmacy and when
taking the medicine; the rate of absorption from modifed-release preparations can vary
between brands

Question 6

Interactions

Answer 6

• Potentially serious hypokalaemia may result from beta2

agonist therapy. Caution required in
severe asthma, because this effect may be potentiated by concomitant use of theophylline,
corticosteroids, and diuretics as well as hypoxia. Plasma potassium should be monitored in
severe asthma
• Increased plasma concentrations with diltiazem, cimetidine, ciprofoxacin, erythromycin,
oestrogens, fuvoxamine, verapamil
• Possible increased risk of convulsions when theophylline given with quinolones
• Reduced plasma concentrations with carbamazepine, primidone, phenobarbital and
phenytoin, ritonavir