Dopamine agonists, such as ropinirole and pramipexole, also work on the dopamine system. They are not as effective as Levo-dopa but have the advantage of causing less dyskinesia (fidgeting). Positive effects of these drugs include lessening of tremor, stiffness and slowness. Pramipexole may also improve mood. Most patients will not get unwanted effects. This said, unwanted effects may again include nausea, dizziness on standing, hallucinations and excessive daytime sleepiness. Rarely patients may experience a side effect called Impulse Control Disorder. This can lead to excessive gambling or shopping, and altered sex drive. Rotigotine is a newer dopamine agonist. It is given as a patch which is stuck to the skin like a plaster. When rotigotine was compared to ropinirole, ropinirole was found to be slightly more effictive. But some patients will find the rotigotine patches more convenient to use than tablets, and its steady absorption even during the night may be an advantage. It has similar side effects to ropinerole. Some patients may get skin irritation. Cabergoline and pergolide are also dopamine agonist drugs. These drugs are now less often used in Derby because of links to cardiac valve problems and scarring of the lungs. Some patients however find cabergoline or pergolide suits them better than the available alternatives. In this case the drug can be used with caution and with monitoring: eg Echocardiogram.

Entacapone is a helper drug. It is sometimes added to L-dopa treatment to help the L-dopa last longer. It can cause dyskinesia but this often improves if the dose of L-dopa is reduced. It may cause discolouration of the urine. Entacapone can be given with Sinemet or Madopar. It is also available combined with Sinemet in a single tablet: Stalevo. Opicapone is a new COMT inhibitor that is taken once daily and tends to cause less diarrhoea than entacapone.

Selegiline and rasagiline belong to a class of drugs called monoamine oxidase inhibitors (MAOIs). They slow the breakdown of dopamine in the brain. They have a fairly mild anti-Parkinsonian effect. They are sometimes used early in PD or they can be added in later on to help smooth the effect of L-dopa. Selegiline has an amphetamine-like metabolite (by-product). This means it can cause insomnia and hallucinations in some people.