Excerpt from PSP/CBD Guide on Sinemet

Several medications, all available only by prescription, can help PSP in some cases.

• Sinemet
This is the brand name for a combination of levodopa and carbidopa. Levodopa is the component that helps the disease symptoms. Carbidopa simply helps prevent the nausea that levodopa alone can cause. When levodopa came along in the late 1960’s, it was a revolutionary advance for Parkinson’s but, unfortunately, it is of only modest benefit in PSP. It can help the slowness, stiffness and balance problems of PSP to a degree, but usually not the mental, speech, visual, or swallowing difficulties. It usually loses its benefit after two or three years, but a few patients with PSP never fully lose their responsiveness to Sinemet.

Some patients with PSP require large dosages, up to 1,500 milligrams (mg.) of levodopa as Sinemet per day to see an improvement, so the dosage should be pushed to at least that level, under the close supervision of a physician, unless a benefit or intolerable side effects occur sooner. The most common side effects of Sinemet in patients with PSP are confusion, hallucinations and dizziness. These generally disappear after the drug is stopped. The most common side effect in patients with Parkinson’s disease, involuntary writhing movements “chorea” or dyskinesias) occur very rarely in PSP, even at high Sinemet dosages.

Patients with PSP should generally receive the standard Sinemet (or generic levodopa/carbidopa) preparation rather than the controlled-release (Sinemet CR or generic levodopa/carbidopa ER) form. The CR form is absorbed from the intestine into the blood slowly and can be useful for people with Parkinson’s disease who respond well to Sinemet but need to prolong the number of hours of benefit from each dose. In PSP, however, such response fluctuations almost never occur. Because Sinemet CR is sometimes absorbed very little or erratically, a poor CR response in a patient with PSP might be incorrectly blamed on the fact that the disease is usually unresponsive to the drug. Such a patient might actually respond to the standard form, which reaches the brain in a more predictable way.

A new formulation of levodopa-carbidopa is Parcopa, which dissolves under the tongue. For people with PSP who cannot swallow medication safely, this could be useful. Another approach for such patients is to crush a regular levodopa-carbidopa tablet into a food or beverage that is easily swallowed. Another new formulation of levodopa-carbidopa (called Stalevo) combines those two drugs with a third drug, entacapone, in the same tablet. The entacapone slows the rate at which dopamine is broken down. It is useful for patients with Parkinson’s whose levodopa-carbidopa works well but only for a few hours per dose. This situation rarely, if ever, occurs in PSP.