Drug interactions
Diltiazem + Theophylline
Severity: Moderate
Diltiazem and Theophylline: moderate interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Diltiazem can raise theophylline concentrations modestly, increasing the risk of toxicity such as nausea, tachycardia or seizures in susceptible patients.
What this interaction means in plain words
Diltiazem and Theophylline can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Diltiazem belongs to Cardiovascular; Theophylline belongs to Respiratory.
Why it happens
Diltiazem inhibits CYP3A4, reducing a minor pathway of theophylline clearance.
What to do
Monitor theophylline serum levels and for toxicity, and lower the dose if levels rise.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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References
- Theophylline (Anhydrous) - FDA drug label (DailyMed) — openFDA / DailyMed
Other interactions of Theophylline
- Riociguat + Theophylline Contraindicated
- Adenosine + Theophylline Major
- Apalutamide + Theophylline Major
- Bupropion + Theophylline Major
- Carvedilol + Theophylline Major
- Cimetidine + Theophylline Major
Other interactions of Diltiazem
- Diltiazem + Flibanserin Contraindicated
- Diltiazem + Ivabradine Contraindicated
- Diltiazem + Lomitapide Contraindicated
- Diltiazem + Lonafarnib Contraindicated
- Acebutolol + Diltiazem Major
- Alfentanil + Diltiazem Major
Frequently asked questions
Can I take Diltiazem with Theophylline?
MediHelp rates the interaction as moderate. Diltiazem and Theophylline can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Diltiazem can raise theophylline concentrations modestly, increasing the risk of toxicity such as nausea, tachycardia or seizures in susceptible patients.
How serious is the interaction between Diltiazem and Theophylline?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor theophylline serum levels and for toxicity, and lower the dose if levels rise.
What other medicines interact with Theophylline?
MediHelp also lists interactions of Theophylline with, for example, Riociguat, Adenosine, Apalutamide. The full list is on the Theophylline page.
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