Furosemide is reported to increase, decrease or to have no effect on
serum theophylline levels. Both
theophylline and loop or thiazide
diuretics can cause hypokalaemia, which may be additive.
If both drugs are used be aware for the potential for changes in
theophylline levels. Consider measuring
theophylline levels, and make appropriate dosage adjust- ments as necessary. It may be prudent to also monitor potassium levels.