Can diltiazem be given to a patient on a beta (beta blocker)?

From the Guidelines

Diltiazem should be used with caution in patients already on beta blockers due to the potential risk of excessive bradycardia and heart block, and its use is generally not recommended as a routine combination 1. When considering the use of diltiazem in a patient on a beta blocker, it's crucial to weigh the potential benefits against the risks. The combination of these two classes of drugs can lead to additive effects on heart rate and blood pressure, potentially resulting in excessive bradycardia, hypotension, or heart failure in susceptible individuals.

• Key considerations include:
  • Starting with lower doses of diltiazem and closely monitoring vital signs, especially during the initial period of co-administration.
  • The potential for drug interactions, particularly with nondihydropyridine calcium channel blockers like diltiazem, which can affect the metabolism of other drugs due to their inhibitory effect on the cytochrome P450 3A4 enzyme 1.
  • Educating patients about the symptoms of excessive heart rate slowing or blood pressure reduction and instructing them to report these promptly.
  • Exercising particular caution in elderly patients and those with pre-existing conduction abnormalities, heart failure, or impaired liver function. However, there are scenarios where the combination of a beta blocker and diltiazem may be considered, such as in the management of uncontrolled rapid atrial fibrillation or in patients who do not respond satisfactorily to separate treatment with either drug class 1.
• In such cases, careful monitoring and dose adjustment are paramount to minimize the risk of adverse effects. It's also worth noting that while the combination may pose risks, it has been used in clinical practice without reports of severe bradycardia necessitating pacemaker treatment in the majority of patients, as observed in the NORDIL study 1.
• Nonetheless, the decision to use diltiazem in a patient on a beta blocker should be made on a case-by-case basis, considering the individual patient's risk factors, the specific clinical scenario, and the potential benefits and risks of the combination therapy.

From the FDA Drug Label

Concomitant use of diltiazem with beta-blockers or digitalis may result in additive effects on cardiac conduction. Experience with the use of diltiazem hydrochloride alone or in combination with beta-blockers in patients with impaired ventricular function is very limited. Caution should be exercised when using the drug in such patients.

Diltiazem can be given to a patient on a beta blocker, but caution should be exercised due to the potential for additive effects on cardiac conduction. The use of diltiazem with beta-blockers in patients with impaired ventricular function is very limited, and therefore, careful consideration should be taken before administering the drug in such cases 2. Key considerations include:

• Monitoring cardiac conduction
• Assessing ventricular function
• Being aware of the potential for symptomatic hypotension or abnormally slow heart rates.

From the Research

Combination Therapy with Diltiazem and Beta Blockers

• Diltiazem can be given to a patient on a beta blocker, but with caution, as the combination may increase the risk of adverse effects such as sinus arrest, atrioventricular block, and bradycardia 3, 4, 5.
• The risk of developing these adverse reactions may be exacerbated in patients with left ventricular dysfunction, latent cardiac conduction deficits, atrioventricular block grade I, bradycardia, or hypotension 3.
• Combination therapy with diltiazem and a beta blocker may be suitable for patients with hypertension or coronary heart disease, but requires close monitoring of blood pressure, heart rate, and atrioventricular conduction on ECG 3.
• Adjustments to the beta blocker dosage may be necessary when combining with diltiazem, especially in patients with impaired renal function 3.

Adverse Effects of Combination Therapy

• Severe bradycardia and conduction abnormalities have been reported in patients on combination therapy with diltiazem and beta blockers 4, 5.
• Cardiogenic shock and sinus bradycardia have been reported in patients on combination therapy with slow-release diltiazem and a beta blocker 5.
• The combination of diltiazem and a beta blocker may increase the risk of bradyarrhythmia, but not with nifedipine-beta-blocker combinations 6.

Clinical Studies and Evidence

• Clinical studies have shown that combination therapy with diltiazem and a beta blocker can be effective in treating angina pectoris in patients with coronary heart disease, but requires caution due to the potential for adverse effects 3, 6.
• A study comparing diltiazem and metoprolol for rate control of atrial fibrillation/flutter in the emergency department found that diltiazem was more effective, with no increased incidence of adverse effects 7.