Gabapentin, an anticonvulsant with an unknown mechanism of action, has recently been approved for use in patients with epilepsy. Observing that a patient with leg cramps and parkinsonism experienced improvement in symptoms after receiving treatment with gabapentin, Olson and colleagues conducted a placebo-controlled, double-blind crossover trial to determine if this medication could lead to symptom improvement in patients with parkinsonism.
Adult patients with symptoms of advanced parkinsonism (Hoehn and Yahr stages: 2.5 to 5) were included in the study. Exclusion criteria included renal or liver disease, Huntington's disease, dystonia, hemiballism, tardive dyskinesia, essential tremor or cerebellar ataxia. The 19 patients who were enrolled had a duration of parkinsonism between two and 21 years (average: 9.3 years), with an average Hoehn and Yahr score of 3.1 There were 13 men and six women. Disability was assessed using a variety of standardized tools, such as the Unified Parkinson's Disease Rating Scale, the Webster Scale and the Hoehn and Yahr Scale.
Patients were randomized to receive either 400 mg of gabapentin for six doses or placebo for six doses over a period of three days. A re-evaluation was then performed, followed by an 11-day washout period. Another evaluation was performed on day 15. Patients who had received the active drug then took placebo; patients who initially took placebo received gabapentin. A final evaluation was then performed. Other medications that the patients received for parkinsonism were not changed during the study.
The total Unified Parkinson's Disease Rating Scale scores were significantly improved when the patients were receiving the active drug versus placebo. Similarly, there was a trend toward improvement in the other scales used for assessment. A subscale evaluating activities of daily living in one of the assesssment tools also showed improvement in the patients receiving gabapentin. The improvements were noted even when the effect of improvement in tremor was accounted for.
Although gabapentin therapy may not be effective in all forms of parkinsonism (in fact, the authors noted worsening of symptoms in patients with progressive supranuclear palsy), the authors conclude that gabapentin seems to improve the symptoms of rigidity, bradykinesia and tremor, all of which can lead to serious impairment of function in patients with parkinsonism. Further studies of gabapentin in parkinsonism are warranted. -- GRACE BROOKE HUFFMAN, M.D.
Olson WL, et al. Gabapentin for parkinsonism: a doubleblind, placebo-controlled, crossover trial. Am J Med 1997;102:60-6.
COPYRIGHT 1997 American Academy of Family Physicians
COPYRIGHT 2004 Gale Group
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