Parkinson's Disease - Medications

Of major concern are reports of a few deaths from liver damage in patients taking tolcapone (Tasmar), another COMT inhibitor. The drug has been taken off the market in many countries and is recommended in the U.S. only for patients who cannot tolerate another other agents. Entacapone does not appear to have the same effects on the liver and does not require monitoring. A 2003 three-year study suggested that the drug is safe and effective over the long term. Still, patients should watch out for symptoms of liver damage, including jaundice (yellowish skin), fatigue, and loss of appetite.

Jaundice is a condition produced when excess amounts of bilirubin circulating in the blood stream dissolve in the subcutaneous fat (the layer of fat just beneath the skin), causing a yellowish appearance of the skin and the whites of the eyes. With the exception of normal newborn jaundice in the first week of life, all other jaundice indicates overload or damage to the liver, or inability to move bilirubin from the liver through the biliary tract to the gut.

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Anticholinergic Drugs

Anticholinergics were the first drugs used for PD, but have largely been replaced by dopamine agents. They are generally used only against tremor in the early stages. They are not as effective against bradykinesia and posture problems and may increase the risk for dementia in late stages. Among the many anticholinergics are trihexyphenidyl (Artane, Trihexy), benztropine (Congentin), biperiden (Akineton), procyclidine (Kemadrin), and ethopropazine (Parisdol). Orphanadrine (Norflex) is a drug with anticholinergic properties, but is also a muscle relaxant and does not cause urinary retention.

Side effects of Anticholinergics. Anticholinergics commonly cause dryness of the mouth (which can actually be an advantage in some people who experience drooling). Other side effects are nausea, urinary retention, blurred vision, and constipation. These drugs can also increase heart rate, worsen constipation, and cause urine retention in men with enlarged prostate. Anticholinergics can sometimes cause significant mental problems, including memory loss, confusion, and even hallucinations, which can be particularly problematic for elderly people with signs of existing dementia and people taking tricyclic antidepressants. People with glaucoma should use these drugs cautiously.

Amantadine

Amantadine (Symadine, Symmetrel) stimulates the release of dopamine and may be used for patients with early mild symptoms. It has some benefit against muscle rigidity and slowness and may help some patients in advanced stages who are unresponsive to other drugs. It is less powerful than levodopa and may lose its effectiveness after about half a year. It may also reduce motor fluctuations brought on by levodopa, however, and these benefits appear to persist for at least a year. Large, well-conducted studies are still needed to determine its true benefits and safety.