Atenolol and Diltiazem: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 15, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Diltiazem
Atenolol
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Diltiazem (a calcium channel blocker) and atenolol (a beta blocker) both slow your heart rate and lower your blood pressure. When you take them together, those effects add up. That can be helpful for some people, but it can also make your heart beat too slowly or your blood pressure drop too low.
You might notice feeling dizzy, tired, or lightheaded, especially when standing up. This matters more if you are older or have a weaker heart. The good news is your care team knows about this pairing and can manage it well by checking your pulse and blood pressure and adjusting your doses if needed. Keep taking both as prescribed and tell your pharmacist or doctor if you feel faint or very slow.
Effect: Additive negative chronotropic, dromotropic, and hypotensive effects. Combining diltiazem (non-dihydropyridine CCB) with atenolol increases risk of bradycardia, hypotension, and AV conduction delay.
- Mechanism: Additive cardiovascular depression at the SA/AV node. Note: atenolol is renally cleared and not hepatically metabolized, so the CYP-related component (reduced beta-blocker metabolism) applies less here than with lipophilic beta blockers; the additive PD effect predominates.
- Onset: Rapid. Evidence: Probable. Severity: Major.
- Monitoring: Heart rate, blood pressure, ECG/PR interval; higher risk in elderly, LV dysfunction, aortic stenosis, or high doses.
What happens
An increased risk of hypotension, bradycardia and slow AV conduction
Interaction Deep Dive
When dilTIAZem is taken together with beta-blockers, the effects on cardiac conduction may be additive 21. This combination slows AV conduction and may heighten the likelihood of bradycardia 1. As a rule, dilTIAZem enhances the pharmacologic actions of beta-adrenergic blocking agents, an effect that can be beneficial in patients whose cardiac function is normal 3. Nevertheless, cases of hypotension, left ventricular failure, and disturbances of AV conduction have been documented following the addition of dilTIAZem to beta blocker therapy. Such events are more apt to arise in elderly individuals and in those with left ventricular dysfunction or aortic stenosis, as well as in patients receiving high doses of either agent 4.
Why it happens (mechanism)
Additive cardiovascular effects, reduced metabolism of some beta blockers
How to manage this interaction
This combination is sometimes used intentionally, but it needs oversight because both drugs slow the heart and lower blood pressure.
- Keep taking both exactly as prescribed unless your prescriber tells you otherwise.
- Your care team may monitor you more closely, checking your pulse, blood pressure, and possibly an ECG, especially at the start or after a dose change.
- Your doses may be adjusted and individualized by your team based on how your heart responds.
- Call your pharmacist or doctor if you feel dizzy, faint, very tired, short of breath, or notice a very slow or irregular pulse.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
6 reports — tap to read
a) DilTIAZem typically enhances the pharmacologic actions of beta-adrenergic blocking drugs, an effect that may benefit patients with normal cardiac function 3. Nevertheless, hypotension, left ventricular failure, and disturbances of AV conduction have been documented when dilTIAZem is combined with beta blocker treatment. Such events are more probable in elderly individuals and in patients with left ventricular dysfunction, aortic stenosis, or those receiving high doses of either agent 4.
b) The hemodynamic tolerability and safety of high-dose intravenous dilTIAZem were assessed in patients with coronary artery disease who were on long-term metoprolol therapy. DilTIAZem promptly lowered systemic vascular resistance, left ventricular systolic pressure, and mean aortic pressure (by 29%, 21%, and 20%, respectively, at 5 minutes), and these values stayed significantly reduced at 30 minutes. There was minimal impact on heart rate or left ventricular contractility. The PQ, QRS, and QTc intervals were unaffected 5.
c) The effects of oral dilTIAZem and propranolol, both individually and combined with placebo, were compared in 12 patients with stable-effort angina. This study found no clinically meaningful reduction in left ventricular function. However, significant bradyarrhythmias and/or systemic hypotension occurred in five of the 12 patients. Every case improved with a decrease in the doses of both dilTIAZem and propranolol. The investigators concluded that high-dose dilTIAZem alone appears to be as effective as, or more effective than, moderate-dose propranolol or the combination of dilTIAZem and propranolol for improving exercise tolerance, myocardial ischemia, and left ventricular function in patients with stable-effort angina 6.
d) DilTIAZem (30 mg orally three times daily) raised the area under the concentration-time curve (AUC) of propranolol and metoprolol by 30% to 40% and also prolonged the elimination half-life of these drugs in 13 healthy volunteers 7. It had no effect on the plasma concentration of atenolol, a beta blocking drug cleared by the kidneys. DilTIAZem reduced propranolol clearance through inhibition of hepatic metabolism. The unbound clearance of both d-propranolol and l-propranolol was decreased. Additionally, propranolol significantly lowered the resting pulse rate following dilTIAZem pretreatment compared with placebo. The pharmacokinetic interaction between these two agents may also contribute to this effect. Other beta blockers metabolized by the liver may be affected in a similar manner 8.
e) Using a randomized, double-blind, Latin-square, placebo-controlled design that included four distinct treatments, eight healthy male Japanese volunteers received a single drop of timolol 0.5% or artificial tears in each eye, with or without a single oral dose of niCARdipine 40 mg and with or without a single oral dose of dilTIAZem 60 mg. A single drop of timolol 0.5% lowered both heart rate and systolic blood pressure, demonstrating that ophthalmic timolol produces systemic effects. Heart rate rose after niCARdipine administration, and this effect was diminished by ophthalmic timolol after exercise. Concurrent use of the timolol eyedrops with both calcium antagonists also reduced systolic blood pressure both at rest and during exercise 9.
f) Giving dilTIAZem together with propranolol in five normal volunteers led to higher propranolol levels in every subject, and the bioavailability of propranolol rose by roughly 50% 2.
Common questions
Can I take Atenolol and Diltiazem together?
Diltiazem and atenolol together can add up to slow your heart and lower your blood pressure, so your care team may adjust doses and watch your pulse and blood pressure closely. Keep taking both as prescribed and report dizziness, fainting, or a very slow heartbeat. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Atenolol and Diltiazem interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How is the Atenolol and Diltiazem interaction managed?
This combination is sometimes used intentionally, but it needs oversight because both drugs slow the heart and lower blood pressure. Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Your care team may monitor you more closely, checking your pulse, blood pressure, and possibly an ECG, especially at the start or after a dose change. Your doses may be adjusted and in… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Atenolol or Diltiazem need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (9)
- Product Information: Lopressor(R) oral tablets, metoprolol tartrate oral tablets. Validus Pharmaceuticals LLC (per FDA), Parsippany, NJ, 2023. DailyMed
- Product Information: CARDIZEM(R) oral tablets, diltiazem hydrochloride oral tablets. Bausch Health US LLC (per FDA), Bridgewater, NJ, 2025. DailyMed
- Glasser SP, Friedman R, Talibi T, et al: Safety and compatibility of betaxolol hydrochloride combined with diltiazem or nifedipine therapy in stable angina pectoris. Am J Cardiol 1994; 73:213-218. PubMed
- Sagie A, Strasberg B, Kusnieck J, et al: Symptomatic bradycardia induced by the combination of oral diltiazem and beta blockers. Clin Cardiol 1991; 14:314-316. DOI
- Wiesfeld AC, Remme WJ, Look MP, et al: Acute hemodynamic and electrophysiologic effects and safety of high-dose intravenous diltiazem in patients receiving metoprolol. Am J Cardiol 1992; 70:997-1003. PubMed
- Hung J, Hackett PL, Gordon SPF, et al: Pharmacokinetics of diltiazem in patients with unstable angina pectoris. Clin Pharmacol Ther 1988; 43:466-470. PubMed
- Tateishi T, Nakashima H, Shitou T, et al: Effect of diltiazem on the pharmacokinetics of propranolol, metoprolol and atenolol. Eur J Clin Pharmacol 1989; 36:67-70. DOI
- Hunt BA, Bottorff MB, Herring VL, et al: Effects of calcium channel blockers on the pharmacokinetics of propranolol stereoisomers. Clin Pharmacol Ther 1990; 47:584-591. PubMed
- Yatsuka YI, Tsutsumi K, & Kotegawa T: Interaction between timolol eyedrops and oral nicardipine or oral diltiazem in healthy Japanese subjects. Eur J Clin Pharmacol 1998; 54:149-154. DOI
Keep reading about Diltiazem
Keep reading about Atenolol
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