Theophylline has a narrow margin between therapeutic and toxic effects and different brands of modified-release theophylline have different bioavailability. Therefore, the brand to be dispensed must be specified.
Before prescribing theophylline consider if a safer, more effective alternative is appropriate. Patients taking theophylline should be reviewed; consider deprescribing and alternative treatments where appropriate.
There is an increased risk of hypokalaemia when theophylline is given with high doses of beta-2 agonists.
Theophylline is metabolised in the liver. The plasma theophylline concentration is increased in heart failure, hepatic impairment, viral infections, in the elderly, and by drugs that inhibit its metabolism. The plasma theophylline concentration is decreased in smokers, by alcohol consumption, and by drugs that induce its metabolism.
Smoking cessation may increase theophylline levels. This is independent of any nicotine replacement therapies that may be prescribed.
Theophylline levels should be checked mainly to avoid toxicity and to ascertain compliance (very low /absent level). Theophylline dose otherwise should be titrated based on symptom relief. For further details on monitoring see SPS.
