Prescribing by brand is recommended for oral formulations due to variations in bioavailability.

Interactions

There are significant drug interactions with theophylline / aminophylline. Consult the BNF, manufacturer's Summary of Product Characteristics (SPC) and specialist textbooks for further information.

Monitoring plasma levels

Therapeutic levels of plasma-theophylline are usually between 10–20mg/litre (55–110micromol/litre), although lower concentrations may be effective in order to achieve satisfactory bronchodilation. Adverse effects can occur within the range 10–20mg/litre and both the frequency and severity increase at concentrations above 20mg/litre.

1. Oral: Plasma-theophylline concentration is measured 5 days after starting oral treatment and at least 3 days after any dose adjustment. A blood sample should usually be taken 4–6 hours after an oral dose of a modified-release preparation (sampling times may vary—consult local guidelines).
2. Parenteral: If aminophylline is given intravenously, a blood sample should be taken 4–6 hours after starting infusion.

Uniphyllin Continus

(Theophylline)

• Modified-release tablets 200mg, 300mg, 400mg (£29.80 = 200mg twice daily)

Indications

• Chronic obstructive pulmonary disease
• Asthma, adults
• Asthma, children

Dose

• Refer to product literature

Notes

1. Prescribe by brand. Theophylline has a narrow therapeutic index and bioavailability differs between brands of oral MR theophylline. Patients should be maintained on the same brand. If a prescription for an oral theophylline MR preparation does not specify a brand name, the pharmacist should contact the prescriber and agree the brand to be dispensed.

Aminophylline

• Injection 250mg/10ml

Notes

1. Particular care needs to be exercised on initiation of therapy. Prescribers who are unfamiliar with the prescribing of this drug are strongly advised to read the Manufacturer's Summary of Product Characteristics (SPC) and the Medusa - the injectable medicines guide.