Clonidine-induced bradycardia in patients with spinal cord injury.

Clonidine is being used increasingly for treatment of spasticity in patients with spinal cord injury. Though hypotension, dry mouth, and constipation are well-documented possible adverse effects, the possibility of clonidine-induced bradycardia is less well recognized and is rare. This report describes a patient who developed spasticity following a traumatic spinal cord injury. After clonidine was initiated, the patient's spasticity improved. However, he developed significant bradycardia. Once clonidine was discontinued, the resting heart rate returned to normal. This case illustrates an unusual adverse effect of clonidine. Possible mechanisms by which clonidine decreases spasticity are described, probable mechanisms of induced bradycardia are reviewed, and specific treatment recommendations for the use of clonidine in spinal cord injured patients are presented.