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Does Mexiletine Hydrochloride Interact with Theophylline?

Mexiletine Hydrochloride and Theophylline have a major drug interaction according to U.S. FDA drug labeling data. Concurrent use may lead to significantly increased plasma theophylline levels (mean 72% increase). Theophylline blood level monitoring recommended when used concurrently with mexiletine. The mechanism involves inhibition of theophylline metabolism. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This information is based on official FDA drug labeling sourced from OpenFDA and the NIH National Library of Medicine.

Severity
Major
Theophylline Class
Methylxanthine
Management
Close medical supervision required
Data Source
U.S. FDA via OpenFDA

How This Interaction Works

The interaction between Mexiletine Hydrochloride and Theophylline occurs because inhibition of theophylline metabolism. Clinically, this means concurrent use may lead to significantly increased plasma theophylline levels (mean 72% increase). theophylline blood level monitoring recommended when used concurrently with mexiletine. This is classified as a major interaction, meaning it could cause serious harm if not properly managed. Your healthcare provider may need to adjust dosages, substitute one medication, or increase monitoring frequency.

What To Tell Your Doctor or Pharmacist

If you are taking Mexiletine Hydrochloride and your doctor is considering prescribing Theophylline (or vice versa), make sure to:

  • Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
  • Ask whether the benefits of combining these medications outweigh the risks for your specific situation
  • Ask what symptoms to watch for that would indicate the interaction is causing problems
  • Ask how frequently you should be monitored while these are co-prescribed
  • Ask whether any dosage adjustments are needed
  • Never stop or change either medication without first consulting your healthcare provider
💊 Mexiletine Hydrochloride(Mexiletine Hydrochloride)+💊 Theophylline(Theophylline)

Severity & Interaction Details

⚠️
major
Use with caution — major interaction
Serious risk of clinically significant harm. Generally avoid; if used, monitor closely.
Severity scale
MinorContra
On record
Yes
Drug A class
—
Drug B class
Methylxanthine
Source
NLP:mexiletine hydrochloride

What this means in plain English

Concurrent use may lead to significantly increased plasma theophylline levels (mean 72% increase). Theophylline blood level monitoring recommended when used concurrently with mexiletine.

What the FDA label says

"Inhibition of theophylline metabolism"

📖 Source: NLP:mexiletine hydrochloride

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Data sourced from U.S. FDA drug labeling via openFDA and the NIH National Library of Medicine. For informational purposes only. Always consult your pharmacist or physician.