Why Flexeril (Cyclobenzaprine) Should Be Avoided in Heart Failure
Flexeril (cyclobenzaprine) is contraindicated in patients with congestive heart failure according to the FDA drug label due to its potential to worsen cardiac function and increase mortality risk. 1
Mechanism and Contraindication
- Cyclobenzaprine is structurally similar to tricyclic antidepressants, which have known negative effects on cardiac function 1
- The FDA explicitly lists congestive heart failure as a contraindication for cyclobenzaprine use 1
- Cyclobenzaprine is also contraindicated in patients with arrhythmias, heart block, or conduction disturbances - conditions that often coexist with heart failure 1
Physiological Effects on the Heart
- Like other tricyclic compounds, cyclobenzaprine can exert negative inotropic effects, potentially worsening cardiac contractility in heart failure patients 2
- The drug may cause anticholinergic effects that can increase heart rate, which is detrimental in heart failure where tachycardia can worsen symptoms and outcomes 2
- Cyclobenzaprine may exacerbate the already compromised hemodynamics in heart failure patients, leading to clinical deterioration 2
Alternative Muscle Relaxants in Heart Failure
- Non-centrally acting muscle relaxants may be safer alternatives in heart failure patients when muscle relaxation is necessary 2
- Any muscle relaxant therapy in heart failure patients should be approached with caution and with close monitoring of cardiac function 2
Broader Context: Other Medications to Avoid in Heart Failure
- Similar to cyclobenzaprine, calcium channel blockers like diltiazem and verapamil are also contraindicated in heart failure with reduced ejection fraction due to their negative inotropic effects 3, 4
- The European Society of Cardiology guidelines specifically warn against using calcium antagonists in heart failure caused by systolic dysfunction 5
- Non-dihydropyridine calcium channel blockers can cause abrupt decompensation and development of pulmonary edema in patients with severe left ventricular dysfunction 6
Clinical Implications
- Patients with heart failure who require muscle relaxation should be evaluated for alternative therapies that don't compromise cardiac function 2
- When prescribing medications for comorbid conditions in heart failure patients, always check for contraindications related to cardiac function 2
- Heart failure patients taking cyclobenzaprine who present with worsening symptoms should have the medication discontinued immediately 1
By avoiding cyclobenzaprine in heart failure patients, clinicians can prevent potential drug-induced worsening of heart failure, which is a preventable cause of clinical deterioration and increased mortality risk.