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Does Theophylline Interact with Cimetidine?

Theophylline and Cimetidine have a major drug interaction according to U.S. FDA drug labeling data. Cimetidine reduces hepatic metabolism of theophylline, increasing blood levels. Adverse clinical effects reported. Alteration less pronounced with 800 mg bedtime dosing. Appropriate monitoring recommended. The mechanism involves inhibition of hepatic microsomal enzyme 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
Cimetidine Class
Histamine-2 Receptor Antagonist
Management
Close medical supervision required
Data Source
U.S. FDA via OpenFDA

How This Interaction Works

The interaction between Theophylline and Cimetidine occurs because inhibition of hepatic microsomal enzyme metabolism. Clinically, this means cimetidine reduces hepatic metabolism of theophylline, increasing blood levels. adverse clinical effects reported. alteration less pronounced with 800 mg bedtime dosing. appropriate monitoring recommended. 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 Theophylline and your doctor is considering prescribing Cimetidine (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
💊 Theophylline(Theophylline)+💊 Cimetidine(Cimetidine)

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
Methylxanthine
Drug B class
Histamine-2 Receptor Antagonist
Source
NLP:cimetidine

What this means in plain English

Cimetidine reduces hepatic metabolism of theophylline, increasing blood levels. Adverse clinical effects reported. Alteration less pronounced with 800 mg bedtime dosing. Appropriate monitoring recommended.

What the FDA label says

"Inhibition of hepatic microsomal enzyme metabolism"

📖 Source: NLP:cimetidine

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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.