Theophylline and
corticosteroids have established roles in the management of asthma and their concurrent use is common. There are isolated reports of increases in
serum theophylline levels (sometimes associated with
toxicity) when oral or
parenteral corticosteroids are given, but other studies have found no changes. The general
clinical importance of these findings is uncertain. Both
theophylline and corticoster- oids can cause hypokalaemia, which may be additive.
The CSM in the UK advises monitoring potassium in severe asthma, because of the probability of multiple potassium-depleting drugs being used, and because some conditions predispose these patients to hypokalaemia (e.g.
hypoxia). Consider monitoring based on the severity of the patient's condition, and the number of potassium-depleting drugs used.