CARBIMAZOLE AND THEOPHYLLINE

Thyroid status may affect the rate at which theophylline is metabolised. In hyperthyroidism it is increased, and so patients require higher theophylline dosages. As thyroid function is corrected (e.g. with carbimazole) theophylline metabolism decreases and so smaller doses are needed. Two case reports describe theophylline toxicity in patients being treated for hyperthyroidism.
Monitor the outcome of resolving hyperthyroidism, checking for theophylline adverse effects (headache, nausea, palpitations). Monitor theophylline levels and adjust the dose as necessary.