Parkinson's Disease - Medications

(Page 3)

Highlights	Diagnosis	Lifestyle Changes
Introduction	Treatment	Resources
Symptoms	Levadopa (L-dopa)	References
Risk Factors	Medications
Complications	Surgery

Catechol-O-Methyl Transferase (COMT) Inhibitors

Catechol-O-methyl transferase (COMT) inhibitors increase concentrations of existing dopamine in the brain. Entacapone (Comtan) is the current standard COMT inhibitor. It improves motor fluctuations related to the wearing-off effect and has shown good results in improving on time and reducing the requirements for L-dopa. If the patient does not respond to the drug within 3 weeks, it should be withdrawn. No one should withdraw abruptly from these drugs.

Side Effects. Side effects include:

Involuntary muscle movements
Mental confusion and hallucinations
Cramps, nausea, and vomiting
Insomnia
Headache
Urine discoloration (a harmless side effect but should be reported to the doctor)
Diarrhea
Less commonly, constipation, susceptibility to respiratory infection, sweating, dry mouth

text continues below

Of major concern are reports of a few deaths from liver damage in patients taking the COMT inhibitor tolcapone (Tasmar). 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 drugs. Entacapone does not appear to have the same effects on the liver and does not require monitoring. A 2003 3-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.

Anticholinergic Drugs

Anticholinergics were the first drugs used for PD, but have largely been replaced by dopamine drugs. 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 (Cogentin), biperiden (Akineton), procyclidine (Kemadrin), and ethopropazine (Parisdol). Orphenadrine (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 and worsen constipation. Anticholinergics can sometimes cause significant mental problems, including memory loss, confusion, and even hallucinations. People with glaucoma should use these drugs cautiously.