From the Guidelines
Methadone can cause bradycardia, particularly at high doses, due to its effects on the cardiovascular system, including QT interval prolongation. Methadone, an opioid medication used for pain management and opioid use disorder treatment, affects the cardiovascular system through several mechanisms, including activating opioid receptors that influence the autonomic nervous system, particularly increasing parasympathetic (vagal) tone 1. This effect is dose-dependent, with higher doses posing greater risk. Patients with pre-existing heart conditions, electrolyte abnormalities, or those taking other medications that affect heart rhythm are at increased risk.
Key Considerations
- Methadone's unique risk profile, including its potential to cause QT prolongation and cardiac arrhythmias, necessitates careful consideration and monitoring when prescribing for pain management 1.
- The risk of bradycardia and other cardiac effects associated with methadone use highlights the importance of healthcare providers closely monitoring patients, especially when initiating therapy or adjusting doses 1.
- Patients should be educated to report symptoms like dizziness, lightheadedness, fainting, or unusual fatigue, which could indicate bradycardia or other cardiac effects 1.
Clinical Recommendations
- Clinicians should exercise caution when prescribing methadone, particularly for patients with risk factors for cardiac complications, and consider alternative treatments when possible 1.
- Baseline and follow-up electrocardiograms are recommended for patients treated with methadone doses greater than 100 mg/day, those with cardiac disease, or when methadone is used in patients taking other medications known to prolong QTc 1.
- Methadone should not be the first choice for an extended-release/long-acting (ER/LA) opioid, and its use should be reserved for clinicians familiar with its unique risk profile and prepared to educate and closely monitor their patients 1.
From the FDA Drug Label
OVERDOSAGE Signs and Symptoms Serious overdosage of methadone is characterized by respiratory depression (a decrease in respiratory rate and/or tidal volume, Cheyne-Stokes respiration, cyanosis), extreme somnolence progressing to stupor or coma, maximally constricted pupils, skeletal-muscle flaccidity, cold and clammy skin, and sometimes, bradycardia and hypotension
- Bradycardia is listed as a possible symptom of serious overdosage of methadone.
- The presence of bradycardia is not guaranteed and is indicated by the word sometimes. Methadone may cause bradycardia in the event of a serious overdosage 2.
From the Research
Methadone and Bradycardia
- Methadone can cause various cardiac complications, including bradycardia, as reported in several studies 3, 4, 5.
- A study published in 2023 found that 4.3% of methadone-poisoned patients experienced sinus bradycardia 3.
- A case report from 2006 described an infant who developed bradycardia after receiving methadone to prevent withdrawal, with the heart rate decreasing to 60-70 beats/min 4.
- Another study published in 2005 reported a case of methadone-induced bradycardia in a patient undergoing opiate detoxification, highlighting the potential for methadone to cause side effects similar to verapamil 5.
- Additionally, a review of the cardiotoxicity of methadone published in 2015 noted that opioids, including methadone, can lead to bradycardia and vasodilation, although this is rare at analgesic doses 6.
Cardiac Complications of Methadone
- The most common cardiac complications of methadone intoxication include sinus tachycardia, QT interval prolongation, and sinus bradycardia 3.
- Methadone can also cause other cardiac effects, such as changes in QT dispersion, pathological U waves, Taku-Tsubo syndrome, Brugada-like syndrome, and coronary artery diseases 7.
- The risk of cardiac complications associated with methadone use highlights the importance of continuous cardiac monitoring and careful patient selection 3, 7, 6.