Theophylline

Question 1

What are other drugs in the same class as theophylline?

Answer 1

Methylxanthines,
oxtriphylline,
dyphylline
Aminophylline

Question 2

What is theophylline used for?

Answer 2

bronchodilator and pulmonary vasodilator

Question 3

What is the mechanism of theophylline?

Answer 3

Theophylline reduces the intracellular hydrolysis of cAMP, inhibiting phosphodiesterase.
The resulting increase in cAMP is associated with bronchial smooth muscle relaxation.

Question 4

What are the main pharmacokinetic/pharmacodynamics characteristics of theophylline?

Answer 4

• Well absorbed throughout GIT
• Half life is shortened in smokers and children
• ~50-70% of circulating drug is bound to plasma proteins in adults
• partitions into saliva and breast milk and across placental barrier.
• metabolised in liver
• metabolites excreted in kidney

Question 5

What are the main precautions when administering theophylline?

Answer 5

• peptic ulcers
• CVD
• hypertension
• hyperthydroidsm
• epilepsy
• eldery
• hypokalaemia
• smoking
• pregnancy nearing delivery, lactation,
• neonates

Question 6

What are some contraindications for theophylline?

Answer 6

• hypersensitivity to xanthines
• coronary artery disease where myocardial stimulation may be harmful
• bronchiolitis

Question 7

What are the common adverse effects which may occur with theophylline?

Answer 7

Dyspepsia
Nausea
GI upset
Headache
Tachycardia

Question 8

What are some drug-drug interactions involving theophylline?

Answer 8

Other xanthines, cimetidine, propranolol, quinolones, OCs, phenobarbitone, phenytoin, carbamazepine, rifampicin, beta agonists, lithium, verapamil, alcohol, tobacco, marijuana, diltiazem, ranitidine, isoniazid, nifedipine, corticosteroids, frusemide, influenza vaccine, st john’s wort,

Question 9

What are common alarm bells we should be aware of with theophylline?

Answer 9

High risk of drug interactions and interpatient variability in dosage requirements.

FEV1 should be monitored to assess efficacy

Plasma theophylline concentration should be monitored. (optimum response 10-20mg/L)

Avoid in acute porphyria (abnormal metabolism of haemoglobin).