Amantadine and a fixed combination of levodopa and carbidopa in the treatment of Parkinson's disease.

Forty-two patients with Parkinson's disease were given amantadine HC1 (Symmetrel) and placebo in an 18 week double-blind cross-over study to determine if amantadine provided additional benefit when combined with levodopa and carbidopa (Sinemet). Analysis of our results showed that amantadine effected a 92% improvement over baseline in symptom scores and a 95% improvement over baseline in activity impairment scores, compared with corresponding values of 4% and 18% for placebo. The difference between amantadine and placebo was statistically significant. Except for one case of mild livedo reticularis and two of blurred vision in the amantadine group, side effects were generally similar for amantadine and placebo in type and frequency. This study provides new evidence of the importance of combinations of antiparkinson drugs to achieve maximum therapeutic benefit.