3.1.3 Theophylline

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


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 10–20 mg/litre (55–110 micromol/litre), although lower concentrations may be effective in order to achieve satisfactory bronchodilation. Adverse effects can occur within the range 10–20 mg/litre and both the frequency and severity increase at concentrations above 20 mg/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®


  • Prolonged release tablets 200mg, 300mg, 400mg (£2.96 = 200mg twice daily)



  • Refer to product literature


  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
Phyllocontin Continus®

Supply Disruption Alert (SDA/2021/003): Phyllocontin® (aminophylline) Continus 225mg and Phyllocontin® Forte Continus 350mg modified-release tablets are being discontinued in the UK. Remaining supplies of the 225mg strength are expected to be exhausted by 2nd March 2021 and the 350mg strength are expected to be exhausted by 5th April 2021.

Update 12/02/2021 - Supply Disruption Alert Update (SDA/2021/003(U)): This update has a revised date of 30th March 2021 for when supplies of the 225mg tablets are expected to be exhausted.

  1. Do not initiate new patients on aminophylline tablets (Phyllocontin® Continus 225mg and Forte Continus 350mg modified-release tablets).
  2. Primary and secondary care services should identify all patients prescribed aminophylline tablets (Phyllocontin® Continus 225mg and Forte Continus 350mg modified-release tablets).
  3. The supply disruption alert includes the following information: actions to be taken for adult and paediatric patients; dose conversion for aminophylline to theophylline for patients who still require a methylxanthine; and advice on monitoring treatment.
  • Injection 25mg in 1ml


  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
Last updated: 13-11-2019


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