How is Parkinson’s disease treated?
Currently, there is no cure for Parkinson’s. But there are drugs available that are used to restore the balance between dopamine and acetylcholine and that can help to control some of the symptoms.

Levodopa is a natural amino acid that has been used to treat Parkinson’s disease since the 1960s. Levodopa is converted into dopamine by an enzyme in the brain. In order to prevent the levodopa being metabolized by this enzyme before it reaches the brain, it is given in combination with an enzyme inhibitor (eg, carbidopa) that blocks the enzyme in the gastrointestinal tract. The inhibitors are not able to pass into the brain and therefore, do not inhibit the conversion of levodopa into dopamine in the brain. Levodopa considerably improves symptoms such as stiffness and slowness of movement. The most commonly prescribed combination is Sinemet (levodopa and carbidopa).

Of those people who respond to treatment with levodopa, around two-thirds will experience some loss of benefit after two to five years as their body becomes tolerant to the drug. Some people will then experience a progressive recurrence of their parkinsonian disability. Other people, especially younger sufferers, will develop fluctuations in their mobility throughout the day. This is known as end-of-dose deterioration or the “wearing-off” effect. Sometimes this effect can be managed by decreasing the time between doses of levodopa. In some people this may not be effective and the change between mobility and immobility may become more abrupt; this is known as the “on/off” effect.

Dopamine agonists stimulate the parts of the brain where dopamine acts. They can be taken alone or sometimes in combination with Sinemet. They produce fewer long-term side effects such as the on/off effect and are therefore often used in younger patients. Commonly prescribed examples are bromocriptine (Parlodel) and ropinirole (Requip). Other drugs in this class that can be prescribed are pramipexole (Mirapex) and rotigotine (Neupro). Apomorphine (Apokyn) is an injectable dopamine agonist that acts very quickly and can be used for people who experience extreme variations in mobility and need to be active at specific times. Cabergoline may be used in combination with levodopa, and pramipexole (Mirapex) may be used alone or in combination with levodopa. Amantadine promotes the release of dopamine and can help to reduce involuntary movements, but as it has only a mild effect is suitable for a smaller number of people.