Mexiletine and Theophylline interaction
Mexiletine and Theophylline: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Mexiletine (Mexiletine Hydrochloride) label · effective 2026-01-15
Concurrent use of mexiletine and theophylline may lead to increased plasma theophylline levels.
One controlled study in eight normal subjects showed a 72% mean increase (range 35 to 136%) in plasma theophylline levels.
If mexiletine and theophylline are to be used concurrently, theophylline blood levels should be monitored, particularly when the mexiletine dose is changed.
An appropriate adjustment in theophylline dose should be considered.
Theophylline plasma levels returned to pre-mexiletine values within 48 hours after discontinuing mexiletine.
From the Theophylline label · effective 2026-01-29
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.