Dopaminergic therapies

The movement-related symptoms of Parkinson’s disease (PD) are caused by the lack of a chemical called dopamine in the brain. At present, PD is mostly treated with medications that replace, or increase, the amount of dopamine in the brain. Medications that are used to restore dopamine levels in this way are called dopaminergic medications.

There are several types of dopaminergic medication. They all aim to increase dopamine levels, but they work in different ways. This means that each medication is better at treating some symptoms than others, and will also produce different patterns of side effects. In addition, different forms of medication delivery (e.g., fast-dissolving or slow-release tablets) are continually being developed to improve treatment convenience/compliance, and to optimise treatment outcomes.

The different dopaminergic medications and the ways in which they work are described in the ‘Medication options’ section, but a summary of available therapies is given in the Table below.

Dopaminergic therapies (brand names may differ between countries)

Levodopa	Levodopa is most commonly prescribed under the brand names Madopar® and Sinemet®. These tablets contain levodopa together with another substance to help it reach the brain (e.g., Sinemet® contains levodopa with carbidopa, and Madopar® contains levodopa with benserazide). The tablets come in many colours and strengths to help with different dose schedules. They are also available as slow-release tablets, or as a gel via the ‘Duodopa® pump’, which may be helpful for some people.
MAO-B inhibitors	Currently, there are two MAO-B inhibitors on the market, rasagiline (Azilect®) and selegiline (Eldepryl®, and Zelapar® – a fast-dissolving tablet).
Dopamine agonists	There are many dopamine agonists on the market, and these include ropinirole (ReQuip®, and ReQuip® LP – a slow-release tablet), cabergoline (Cabaser®), bromocriptine (Parlodel®), pergolide (Celance®), pramipexole (Mirapexin®), and rotigotine (Neupro® – an adhesive skin patch). In addition, apomorphine (Apo-Go®) is given by injection to produce rapid control of symptoms in people with advanced PD. Apomorphine is not related to the medical use of morphine in any way.
COMT inhibitors	There are two COMT inhibitors currently available, entacapone (Comtess®) and tolcapone (Tasmar®). COMT inhibitors are only effective when taken together with levodopa, and entacapone is available as Stalevo® – a combination tablet that also contains levodopa and carbidopa (available without entacapone as Sinemet®, see above).