Beta Blockers Do Not Cause Spasticity
Beta blockers are not known to cause spasticity or spastic movements. The cardiovascular side effects of beta blockers are well-documented and include bradycardia, hypotension, cold extremities, and fatigue, but spasticity is not among them 1.
Known Neurological Side Effects of Beta Blockers
The established adverse effects of beta blockers that affect movement or sensation include:
- Cold extremities due to peripheral vasoconstriction, particularly with non-selective agents (beta-1 selective agents like metoprolol, atenolol, and bisoprolol cause fewer peripheral vascular effects) 1, 2
- Fatigue occurs in approximately 0.4% of patients 1
- Bradycardia from cardiac inhibition 1
Spasticity: Actual Causes and Treatments
Spasticity is a velocity-dependent increase in muscle tone resulting from upper motor neuron dysfunction due to interruption of inhibitory descending spinal motor pathways 3, 4. The pathophysiology involves overactivity of the alpha motor neuron 3.
Common causes of spasticity include:
Established treatments for spasticity (not beta blockers) include:
- Baclofen (centrally acting GABA agonist) 3, 7
- Benzodiazepines like diazepam 3, 7
- Tizanidine (alpha-2 agonist) 3, 7
- Dantrolene (peripherally acting) 3, 7
- Botulinum toxin injections 4, 6
- Intrathecal baclofen for severe cases 3, 7
Clinical Distinction
Interestingly, beta blockers are mentioned in the spasticity literature as potential treatments (specifically thymoxamine and other beta blockers were studied as antispastic agents), though they are not standard therapy 7. This further confirms that beta blockers do not cause spasticity—they were actually investigated for the opposite effect.
Important Caveat
If a patient on beta blockers develops abnormal movements, consider alternative diagnoses such as tremor (which beta blockers can sometimes worsen or unmask), drug-induced movement disorders from other medications, or underlying neurological conditions unrelated to the beta blocker 1.