Baclofen-induced cough suppression in cervical spinal cord injury cord injury

Objective: To determine the effect of the GABA-agonist baclofen on cough reflex sensitivity in subjects with cervical spinal cord injury (C-SCI). Baclofen has been shown to inhibit the cough reflex in able-bodied volunteers. Design: Prospective, nonrandomized control trial. Setting: Veterans Affairs medical center with large outpatient SCI population. Participants: Twelve adult males (11 outpatients) with C-SCI chronically maintained on oral baclofen for the treatment of muscle spasm. Intervention: Subjects underwent cough challenge testing with inhaled capsaicin. The concentrations (μM) of capsaicin inducing 2 or more (C₂) and 5 or more (C₅) coughs were determined. Mean values for log C₂ and log C₅ were compared with a control group of outpatients with C-SCI not receiving baclofen. Results: Subjects treated with baclofen had a significantly higher cough threshold (diminished cough reflex sensitivity) than control subjects. Mean (± standard error of the mean) values for log C₂ in study subjects and controls were 1.28 ±. 16 and .65 ± .15, respectively (p = .009). Mean values for log C₅ in subjects receiving baclofen and in control subjects were 2.20 ± .22 and 1.43 ± .23, respectively (p = .024). Subjects and controls did not differ in terms of age, spirometric parameters, or duration of injury. Conclusions: The results suggest that chronic therapy with baclofen diminishes cough reflex sensitivity in subjects with C-SCI. The clinical significance of this finding remains to be elucidated. (C) 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.