Is it safe for a patient with a history of myocardial infarction (heart attack) to take cyclobenzaprine?

Cyclobenzaprine Safety in Patients with History of Myocardial Infarction

Cyclobenzaprine is absolutely contraindicated in patients during the acute recovery phase of myocardial infarction and should be avoided in patients with a history of MI who have arrhythmias, heart block, conduction disturbances, or congestive heart failure. 1

FDA Contraindications

The FDA drug label explicitly lists the following as absolute contraindications for cyclobenzaprine use 1:

• Acute recovery phase of myocardial infarction
• Patients with arrhythmias
• Heart block or conduction disturbances
• Congestive heart failure

Mechanism of Concern

Cyclobenzaprine is structurally related to tricyclic antidepressants (such as amitriptyline and imipramine), and these medications have been reported to produce 1:

• Arrhythmias
• Sinus tachycardia
• Prolongation of cardiac conduction time
• Myocardial infarction
• Stroke

Clinical Decision Algorithm

If the MI was recent (acute recovery phase):

Do not prescribe cyclobenzaprine under any circumstances. 1 The acute recovery phase typically extends through the first several weeks to months post-MI, during which cardiac remodeling and electrical instability are most pronounced.

If the MI was remote (beyond acute phase):

Assess for the following contraindications before considering cyclobenzaprine 1:

1. Current arrhythmias → Absolute contraindication
2. Heart block or conduction disturbances → Absolute contraindication
3. Congestive heart failure → Absolute contraindication
4. Hyperthyroidism → Absolute contraindication

If any of these conditions are present, do not prescribe cyclobenzaprine.

If no contraindications are present:

Even in patients with remote MI and no current cardiac complications, extreme caution is warranted given cyclobenzaprine's tricyclic structure and potential for cardiac toxicity. 1 Consider alternative muscle relaxants with safer cardiac profiles.

Common Pitfalls

• Do not assume "old MI" means safe use – the presence of residual conduction abnormalities, arrhythmias, or heart failure makes cyclobenzaprine contraindicated regardless of how long ago the MI occurred. 1

• Recognize that cyclobenzaprine can cause ST-segment elevation on ECG – this has been reported in overdose situations and could complicate the clinical picture in a patient with cardiac history. 2

• Be aware of drug interactions – cyclobenzaprine enhances effects of other CNS depressants and can cause life-threatening serotonin syndrome when combined with SSRIs, SNRIs, TCAs, tramadol, or MAO inhibitors. 1

Safer Alternatives

For muscle spasm management in post-MI patients, consider non-pharmacologic approaches or medications without tricyclic structure and cardiac contraindications, as cyclobenzaprine's cardiac risks outweigh benefits in this population. 1