Amantadine

Introduction Amantadine was first found to be an effective medication for PD about 30 years ago, when a patient was treated with Amantadine as a prevention of influenza (Schwab R, 1969): this medication was first used as anti-virus treatment. Coincidentally, this patient had PD, and the symptoms of PD were reduced following Amantadine treatment. In other words, the discovery of the beneficial effect of Amantadine in PD patients occurred by chance.

Despite initial enthusiasm in this medication, Amantadine gradually became almost forgotten. This was because its benefit in PD was subsequently reported to be short-lasting, i.e. just a few months (Yahr and Duvoisin, 1972).

However, by the late 1990's, there was a resurgence of interest in Amantadine. This occurred following several reports of its efficacy in reducing dyskinesia in PD (Rajput AH et al, 1998: Verhagen ML et al, 1998). This discovery was crucial because dyskinesia, an uncontrollable movement that appeared as "chaotic, dancing" movement, has been reported to be a frequent complication in the treatment of PD. As many as 50% of PD patients developed dyskinesia after 3-5 years of treatment. When established, dyskinesia is irreversible, difficult to treat and potentially disabling. Thus, Amantadine has found its role again in the treatment of PD about 30 years after its discovery.

What is Amantadine?

The biochemical ingredient is Amantadine Sulphate. This medication, which is also known as PK-Merz, is the product of Merz Pharma.

What are the benefits of Amantadine in PD?

Amantadine blocks the effect of glutamate, a biochemical substance which is hyperactive in PD. This leads to relief of symptoms of PD such as tremor, stiffness and slowness of movement. Amantadine treatment also helps in reducing the daily dose of other PD medications. The early use of amantadine as single medication (monotherapy) makes it possible to delay the use of levodopa treatment, which is responsible for the development of dyskinesia. In contrast to the older reports, the recent studies have shown that the effect of Amantadine lasts for up to 5.5 years (Greulich W, 1995).

In addition, Amantadine has other beneficial effects in PD. One of them is possible protective effect on the brain cells in PD. This is particularly important as there is no cure for this illness, and thus any treatment that can slow down the disease progression is crucial. Amantadine also improves the mood and vigilance (alertness) of PD patients.

What are the side effects of Amantadine?

The side effects of treatment with Amantadine are sleep disturbances, confusion, discoloration of skin and leg swelling. Sleep disturbances usually occur if the last dose is taken in the late afternoon (after 4 pm). Confusion can be minimized by increasing the dose slowly. The skin discoloration improves when the dose is reduced. There is not need to be alarmed by the leg swelling due to Amantadine because it has nothing to do with kidney or heart problems.

Overall, Amantadine is a safe medication if patients are adequately monitored.

What is the dosage of Amantadine?

Each tablet contains 100 mg of Amantadine sulphate. The effective dose ranges from 200 to 600 mgs per day.

Conclusion

The reemergence of Amantadine is good news for PD patients as it provides them a new treatment option. The relief of dyskinesia by Amantadine in PD patients is particularly useful as a temporary measure to control this uncontrollable and frequently disabling movement prior to brain surgery. Amantadine is beneficial for PD patients who are in both the early and late stage of illness.

References
Greulich W, Fenger E. Amantadine in Parkinson's disease: pro and contra. J Neural Transm 1995; 46 Suppl: 415-421.

Rajput AH, Rajput A, Lang AE, et al. New use for an old drug: Amantadine benefits levodopa-induced dyskinesia. Mov Disord 1998; 13: 851 (Letter).

Schwab R, England A, Poskanzer D, Young R. Amantadine in the treatment of Parkinson's disease. J Am Med Assoc 1969; 280: 1168-1170.

Verhagen ML, Del Dotto P, van den Munckhof P, et al. Amantadine as treatment for dyskinesia and motor fluctuations in Parkinson's disease. Neurology 1998; 50: 1323-1326.

Yahr MD, Duvoisin RC. Drug therapy of parkinsonism. N Eng J Med 1972; 287: 20-24.