Can Cardizem (Diltiazem) cause tachycardia?

From the Guidelines

Cardizem (diltiazem) is not typically associated with causing tachycardia, and it is often used to treat supraventricular tachycardia, as recommended by the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1. However, in rare cases, Cardizem can paradoxically cause tachycardia through a phenomenon called "reflex tachycardia." This occurs when the medication lowers blood pressure significantly, triggering the body's compensatory mechanisms to increase heart rate. Some key points to consider when using Cardizem for treating tachycardia include:

• The medication is recommended for acute treatment in hemodynamically stable patients with focal atrial tachycardia, as stated in the guideline 1.
• Close monitoring is recommended during intravenous drug therapy to evaluate for hypotension or bradycardia, as noted in the guideline 1.
• Patients experiencing unexpected rapid heart rate while taking Cardizem should contact their healthcare provider immediately, as this could indicate an adverse reaction or that the medication regimen needs adjustment.
• It's essential not to discontinue Cardizem without medical supervision, as sudden cessation can worsen cardiovascular conditions. In general, the use of Cardizem for treating tachycardia is supported by the guideline, which recommends intravenous beta blockers, diltiazem, or verapamil for acute treatment in hemodynamically stable patients with focal atrial tachycardia 1.

From the FDA Drug Label

As with other agents which slow AV nodal conduction and do not prolong the refractoriness of the accessory pathway (e.g., verapamil, digoxin), in rare instances patients in atrial fibrillation or atrial flutter associated with an accessory bypass tract may experience a potentially life-threatening increase in heart rate accompanied by hypotension when treated with injectable forms of diltiazem

• Tachycardia can be a potential effect of diltiazem (Cardizem) in certain patients, specifically those with atrial fibrillation or atrial flutter associated with an accessory bypass tract.
• This is because diltiazem can slow AV nodal conduction without prolonging the refractoriness of the accessory pathway, leading to a potentially life-threatening increase in heart rate in rare instances 2.

From the Research

Cardizem and Tachycardia

• Cardizem, also known as diltiazem, is a calcium channel blocker used to treat various cardiovascular conditions, including hypertension, angina, and supraventricular arrhythmias 3, 4.
• The medication is known to lower heart rate, which is beneficial in treating conditions such as atrial fibrillation and stable chronic angina 5, 6.
• However, there is no direct evidence to suggest that Cardizem causes tachycardia. In fact, the medication's heart rate-lowering property is considered a contributing factor to its clinical effectiveness in treating ischemic heart disease and hypertension 5.
• It is worth noting that while diltiazem can cause atrioventricular block, a condition that can lead to bradycardia, the risk of this adverse effect is rare and may be exacerbated by concomitant beta-adrenoceptor antagonist therapy 3, 7.
• Overall, the available evidence suggests that Cardizem is not likely to cause tachycardia, but rather is used to treat conditions characterized by abnormal heart rhythms, including supraventricular tachycardia 3, 6.