What happens if you give Cardizem (diltiazem) to a patient with bradycardia?

From the Guidelines

Administering Cardizem (diltiazem) to a patient with bradycardia is contraindicated and potentially dangerous. Diltiazem is a calcium channel blocker that slows heart rate and cardiac conduction, which would further worsen bradycardia (heart rate below 60 beats per minute) 1. This medication works by blocking calcium entry into cardiac cells, reducing the heart's contractility and slowing conduction through the AV node. In a patient already experiencing bradycardia, diltiazem could precipitate severe bradycardia, heart blocks, hypotension, cardiovascular collapse, or even cardiac arrest.

Key Considerations

• Healthcare providers should avoid diltiazem in patients with pre-existing bradycardia, sick sinus syndrome, or high-degree AV blocks unless they have a functioning pacemaker 1.
• If a patient on diltiazem develops bradycardia, the medication should be discontinued immediately, and supportive measures should be initiated, potentially including atropine, cardiac pacing, or calcium gluconate administration to reverse calcium channel blockade effects 1.
• Always assess a patient's baseline heart rate and rhythm before administering any rate-controlling medications.

Recommendations

• For patients with bradycardia, alternative treatments should be considered, such as atropine or cardiac pacing, depending on the underlying cause and severity of the bradycardia 1.
• In cases where diltiazem is necessary for other medical conditions, close monitoring of the patient's heart rate and rhythm is crucial to prevent worsening bradycardia 1.

From the FDA Drug Label

WARNINGS Cardiac Conduction Diltiazem hydrochloride prolongs AV node refractory periods without significantly prolonging sinus node recovery time, except in patients with sick sinus syndrome. This effect may rarely result in abnormally slow heart rates (particularly in patients with sick sinus syndrome) or second, or third degree AV block

• Bradycardia: Giving Cardizem (diltiazem) to a patient with a heart rate of 58 (bradycardia) may worsen the condition, as diltiazem can prolong AV node refractory periods, potentially resulting in abnormally slow heart rates.
• Key Consideration: Patients with sick sinus syndrome are particularly at risk, and the use of diltiazem in these patients may require careful monitoring.
• Clinical Decision: Administering diltiazem to a patient with bradycardia should be done with caution, and the patient's heart rate should be closely monitored 2.

From the Research

Administration of Cardizem to a Patient with Bradycardia

• Giving Cardizem (diltiazem) to a patient with a heart rate of 58, which is considered bradycardia, can lead to severe adverse effects, as evidenced by several studies 3, 4, 5, 6, 7.
• The combination of diltiazem and beta-blockers can cause symptomatic bradycardia, as seen in ten patients who were admitted to the Intensive Coronary Care Unit 4.
• In patients with bradycardia, the use of diltiazem can lead to junctional bradycardia, hypotension, and reduced cardiac function, as observed in a case of massive overdose 5.
• The concomitant use of beta-blockers and calcium channel blockers, such as diltiazem, can cause profound sinus bradycardia, and this effect may be more than additive when the two classes of drugs are used together 6.
• Treatment of diltiazem-induced bradycardia may involve temporary cardiac pacing, infusion of dopamine, and other supportive measures, as seen in cases of poisoning with calcium channel blockers 7.

Key Considerations

• The use of diltiazem in patients with bradycardia requires caution, especially in the elderly or in patients with left ventricular dysfunction or antecedent sinoatrial or atrioventricular conduction abnormality 4.
• The combination of diltiazem and beta-blockers should be avoided in hypertensive patients, as it can lead to severe adverse reactions, including cardiogenic shock and extreme bradycardia 3.
• In cases of diltiazem overdose, treatment is based on general measures of intoxication support, decreasing the drug absorption, and improvement of cardiac function, with the use of intravenous calcium, glucagon, atropine, and pacemaker, as needed 7.