Drug interactions
Diltiazem + Labetalol
Severity: Major
Diltiazem and Labetalol: major interaction.
Last updated Sources: UK SmPC
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 slows AV conduction and heart rate, and labetalol has beta-blocking activity. Together they can cause bradycardia, AV block, hypotension and worsening of heart failure.
What this interaction means in plain words
Diltiazem and Labetalol can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Diltiazem belongs to Cardiovascular; Labetalol belongs to Cardiovascular.
Why it happens
Additive negative chronotropic, dromotropic and inotropic effects; diltiazem may also modestly raise beta-blocker levels via CYP3A4 inhibition.
What to do
Avoid in patients with conduction abnormalities or reduced ejection fraction. Otherwise monitor ECG, heart rate and blood pressure closely and reduce doses as needed.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Diltiazem and Labetalol, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
References
Other interactions of Labetalol
- Amifostine + Labetalol Major
- Amiodarone + Labetalol Major
- Atenolol-chlorthalidone + Labetalol Major
- Atenolol + Labetalol Major
- Betaxolol + Labetalol Major
- Bisoprolol + Labetalol 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 Labetalol?
MediHelp rates the interaction as major. Diltiazem and Labetalol can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Diltiazem slows AV conduction and heart rate, and labetalol has beta-blocking activity. Together they can cause bradycardia, AV block, hypotension and worsening of heart failure.
How serious is the interaction between Diltiazem and Labetalol?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid in patients with conduction abnormalities or reduced ejection fraction. Otherwise monitor ECG, heart rate and blood pressure closely and reduce doses as needed.
What other medicines interact with Labetalol?
MediHelp also lists interactions of Labetalol with, for example, Amifostine, Amiodarone, Atenolol-chlorthalidone. The full list is on the Labetalol page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
