Terbutaline in myasthenia gravis: A pilot study

The objective of this study was to assess the short-term efficacy and safety of terbutaline, a β2-adrenergic agonist, in patients with myasthenia gravis (MG) in a randomized, double-blind, placebo-controlled, crossover study. The primary endpoint for efficacy was a reduction of at least 3 points in the quantitative MG score (QMGS). Secondary endpoints included changes in the functional disability scale (FDS), forced vital capacity (FVC), grip strength, anti-acetylcholine receptor (AChR) antibody levels and decremental response. During the terbutaline phase, five of eight (63%) patients had an improvement in the QMGS of 3.0 or greater, while 3/8 (38%) patients had improvement in the FDS of one grade. No improvement was seen during the placebo period. Statistical analysis using Wilcoxon signed-rank test confirmed that terbutaline treatment resulted in a significant improvement in QMGS. There was no change in FVC, grip strength or anti-AChR antibody levels, but there was an improvement in the decremental response during terbutaline phase. Terbutaline was well-tolerated in all study subjects. We conclude that terbutaline may be an effective adjunct therapy in a subset of patients with myasthenia, although confirmation with larger trials will be required.