Because Parkinson's disease results from the death of brain cells that produce dopamine, nearly all current drug therapies try to replace this important nerve chemical or protect it from enzymes in the body that break it down.

• Levodopa (sold as Sinemet or generic levodopa/carbidopa) dramatically liberated Parkinson's disease patients from wheelchairs when it first became available in the 1960s. Converted within the brain into dopamine, this drug is still the gold standard therapy for alleviating the core Parkinson's motor symptoms of slowness, stiffness, and tremor.
• Dopamine agonists (Apokyn, Mirapex, Parlodel, Requip) are compounds that can activate the same receptor as dopamine, thus mimicking its effects. These are less potent than Sinemet but generally cause fewer long-term side effects. Many early Parkinson's patients start out on Mirapex or Requip alone. Still, dopamine agonists are most commonly used in combination with Sinemet.
• MAO-B inhibitors (Azilect, Eldepryl, Zelapar) enhance dopamine's effects by preventing its breakdown within the brain.
• COMT inhibitors (Comtan, Tasmar) are prescribed with levodopa. They prolong its effects by shielding it from being degraded in the bloodstream.
• Amantadine (Symmetrel) is an antiviral drug thought to boost the release of dopamine in the brain.
• Anticholinergics (such as Artane, Cogentin) help relieve tremor and drooling by adjusting the balance in the brain between dopamine and another brain chemical called acetylcholine. These drugs are used less often in older patients because of side effects.