Theophylline Flashcards
What are other drugs in the same class as theophylline?
Methylxanthines,
oxtriphylline,
dyphylline
Aminophylline
What is theophylline used for?
bronchodilator and pulmonary vasodilator
What is the mechanism of theophylline?
Theophylline reduces the intracellular hydrolysis of cAMP, inhibiting phosphodiesterase.
The resulting increase in cAMP is associated with bronchial smooth muscle relaxation.
What are the main pharmacokinetic/pharmacodynamics characteristics of theophylline?
- 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
What are the main precautions when administering theophylline?
- peptic ulcers
- CVD
- hypertension
- hyperthydroidsm
- epilepsy
- eldery
- hypokalaemia
- smoking
- pregnancy nearing delivery, lactation,
- neonates
What are some contraindications for theophylline?
- hypersensitivity to xanthines
- coronary artery disease where myocardial stimulation may be harmful
- bronchiolitis
What are the common adverse effects which may occur with theophylline?
Dyspepsia Nausea GI upset Headache Tachycardia
What are some drug-drug interactions involving theophylline?
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,
What are common alarm bells we should be aware of with theophylline?
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).
