Albuterol Improves Response to Levodopa and Increases Skeletal Muscle Mass in Patients With Fluctuating Parkinson Disease
Animal studies indicate that beta(2)-adrenergic receptor agonists enhance transport of levodopa across the blood-brain barrier. Preliminary studies showed improved response to levodopa in patients with Parkinson disease (PD) who were given albuterol as adjunctive therapy. Beta(2)-adrenergic agonists may offer additional benefits to PD patients via their skeletal muscle anabolic effects, particularly those who experience decreased muscle strength and weight loss. Nondemented, fluctuating PD patients receiving levodopa but not experiencing severe dyskinesias underwent the following tests at baseline and 14 weeks after treatment with albuterol sulfate (4 mg four times a day, orally): Unified Parkinson's Disease Rating Scale motor, tapping, and stand-walk-sit tests every 30 minutes between 8 am and 5 pm; body composition analyses using whole-body plethysmography and computed tomography of the thigh; muscle strength tests; and the Parkinson's Disease Questionnaire (PDQ-39). Results were analyzed using paired t-tests (2 tailed), repeated-measures analysis of variance, and the Wilcoxon signed-rank test. Seven of 8 enrolled patients completed the study; 1 patient withdrew because of headache and anxiety. The area under the curve for all-day UPDRS motor scores improved by 9.8 +/- 9.1% (mean +/- standard deviation; P < 0.05) and tapping improved by 7.6 +/- 8.1% (P < 0.05). The effect was more pronounced when only the response to the first levodopa dose (area under the curve, 8-11 am) was analyzed: 13.0 +/- 9.8% and 9.8 +/- 9.6% respectively. Thigh muscle cross-sectional area increased significantly as measured by computed tomography (5.3 +/- 3.2%, P < 0.01), as did fat-free mass by whole-body plethysmography combined with total-body water determination (9.5 +/- 2.9%, P < 0.05). There was no significant improvement in the stand-walk-sit test, muscle strength tests, other UPDRS sections, daily OFF time, or PDQ-39. Four patients were rated as having a mild global improvement (+1 point) on a -3 to +3-point scale, and 3 of them chose to continue albuterol beyond the termination of the study. The mean heart rate increased from 78.3 +/- 9.3 beats/minute to 85.6 +/- 8.7 beats/minute (P < 0.05). No laboratory abnormalities or electrocardiographic changes were induced by albuterol in any subject. This open-label pilot study suggests that albuterol increases muscle mass and improves the therapeutic response to levodopa in patients with fluctuating PD. A double-blind, placebo-controlled study is needed to confirm the effects and safety profile of beta(2)-agonists in PD.
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