From the FDA Drug Label
Contraindications Section Hypersensitivity to any component of this product. Concomitant use of monoamine oxidase (MAO) inhibitors or within 14 days after their discontinuation. Hyperpyretic crisis seizures, and deaths have occurred in patients receiving cyclobenzaprine (or structurally similar tricyclic antidepressants) concomitantly with MAO inhibitor drugs. Acute recovery phase of myocardial infarction, and patients with arrhythmias, heart block or conduction disturbances, or congestive heart failure. Hyperthyroidism.
Cyclobenzaprine is contraindicated in patients with certain heart conditions, including:
- Acute recovery phase of myocardial infarction
- Arrhythmias
- Heart block or conduction disturbances
- Congestive heart failure Therefore, cyclobenzaprine is not safe to use in patients with these heart conditions 1.
From the Research
Cyclobenzaprine should generally be avoided in patients with heart disease due to its potential to cause cardiovascular effects, including arrhythmias, tachycardia, and heart block, particularly in patients with pre-existing cardiac conditions. This muscle relaxant has a chemical structure similar to tricyclic antidepressants, which can contribute to its cardiac side effects 2. The medication works by acting on the central nervous system to reduce muscle hyperactivity without directly affecting muscle fibers, but this mechanism also contributes to its potential cardiac side effects.
Key Considerations
- Cyclobenzaprine is specifically contraindicated in patients with heart block, conduction disturbances, heart failure, or recent myocardial infarction.
- For patients with heart disease who need muscle relaxation, alternative medications like methocarbamol (Robaxin) or tizanidine (Zanaflex) may be safer options, though tizanidine requires careful blood pressure monitoring 3.
- If cyclobenzaprine must be used in a patient with stable, less severe heart disease, it should be prescribed at the lowest effective dose (typically 5mg rather than 10mg), for the shortest duration possible (usually 2-3 weeks maximum), and with careful cardiac monitoring.
Evidence Summary
The most recent and highest quality study on the topic is from 2022, which highlights the potential of cyclobenzaprine to cause sedative effects via off-target antagonism of central histamine H1 receptors 2. Other studies, such as those from 2003 and 2004, provide evidence on the efficacy and safety of cyclobenzaprine in patients with musculoskeletal conditions, but do not directly address its use in patients with heart disease 4, 3. A 2016 study from the American Heart Association provides guidance on drugs that may cause or exacerbate heart failure, which includes cyclobenzaprine 5. Overall, the evidence suggests that cyclobenzaprine should be used with caution in patients with heart disease, and alternative medications should be considered when possible.