[NB: In February 2021, Phyllocontin® (Aminophylline) 225mg and 350mg modified release tablets were discontinued in the UK]
Issues for Surgery
Advice in the Perioperative period
Ensure that the patient is maintained on a specific manufacturer’s product (see Further Information).
For patients who may decide to quit smoking during the perioperative period see Further Information.
Interaction(s) with Common Anaesthetic Agents
The clinical significance of the following interactions is unclear – bear them in mind in case of an unexpected response to treatment1.
Ketamine / Esketamine
The UK manufacturer of esketamine states that it may lower the seizure threshold when used concomitantly with theophylline and advise that this combination should be avoided1, 2.
Interaction(s) with other Common Medicines used in the Perioperative Period
Theophylline Toxicity (see Further Information)
Theophylline clearance can be reduced by erythromycin (onset may be delayed for 2 – 7 days)1, 2, 5. In some cases this has led to increased theophylline levels, and toxicity may develop. Monitor theophylline levels after 48 hours and adjust the dose accordingly. Consider using an alternative antimicrobial if possible1.
In general clarithromycin does not interact with theophylline but there are isolated reports of possible theophylline toxicity with concomitant use1, 4, 5. A clinically relevant interaction seems unlikely; however, consider the interaction if any unexplained reduction in theophylline efficacy or adverse effects (e.g. headache, nausea) occur, and monitor theophylline concentrations accordingly1.
Risk of Seizures
Seizures have developed in 2 patients taking theophylline when given with imipenem – the general relevance of this interaction is unclear1, 2.
Macrolide Antibiotics (also see Theophylline Toxicity above)
Concomitant administration of theophylline and dexamethasone or hydrocortisone can increase the risk of hypokalaemia2, 4, 5. This is unlikely to be an issue where corticosteroids are used as single doses to reduce post-operative nausea and vomiting or as cover for patients at risk of adrenal insufficiency. However, bear this interaction in mind should continued corticosteroid treatment be necessary post-operatively.
Monitor potassium levels closely1.
Theophylline Drug Interactions, Monitoring and Toxicity