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 (microM) 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.