The treatment of PD can be challenging, but unlike other neurodegenerative diseases, there is effective symptomatic treatment. While medical and surgical therapy can provide long-lasting benefits, the goal of therapeutics in PD is neuroprotection (the development of drugs that can halt or slow down the progression). To date, no medication has demonstrated definite neuroprotection. However, monoamino oxidase inhibitors (MAOB-I) like rasagiline (Azilect®) may have disease modifying effects.
There are also several other agents that have shown sufficient promise to warrant larger trials (CoQ10, creatine). These are the most common medications used for the symptomatic treatment of symptoms:
- Levodopa: also called L-dopa, is currently the single most effective drug for the treatment of PD. It is converted into dopamine in the brain, the neurotransmitter produced by cells in the substantia nigra. Levodopa helps control the main motor symptoms of PD. It is generally taken with another drug, carbidopa, to avoid its most common side effect, nausea. In the United States, this combination is commercialized under the name carbidopa-levodopa, Sinemet®, Sinemet® CR, or StaLevo®, a single pill containing carbidopa, levodopa and entacapone. There is controversy about how early in the disease levodopa therapy should be initiated.
- Dopamine agonists: are drugs that stimulate dopamine receptors directly in the brain, mimicking the effect of levodopa. These medications are used to treat the motor symptoms of PD, particularly early in the disease and in younger patients. They are not as potent as levodopa, but they delay the onset of motor complications associated with chronic levodopa use. Agonists currently available in the United States are pramipexole (Mirapex®), ropinirole (Requip®), and apomorphine (Apokyn®). The rotigotine patch (Neupro®) was withdrawn from the United States market in April 2008, but it is still available in other countries.
- COMT inhibitors: prevent the breakdown of dopamine in the brain. When taken with levodopa, the effect of a single dose is prolonged. The two COMT inhibitors available in United States are entacapone (Comtan®) and tolcapone (Tasmar®). A combination of levodopa, carbidopa and entacapone in a single tablet is available as StaLevo®.
- Monoaminooxidase inhibitors (MAOB-I): Selegiline (Eldepryl®, Zelapar®) and rasagiline (Azilect®), the two MAOB-I commercially available for the treatment of PD, also inhibit the breakdown of dopamine in the brain, prolonging its effect. Recent trials suggest that rasagiline may have disease-modifying effects (neuroprotection). An older study on selegiline indicated that the medication also slowed down the disease. The results were however inconclusive, as the benefit could have also been explained by its symptomatic effects.
- Anticholinergic medications: are drugs that block the effect of the chemical acetylcholine in the brain. Acetylcholine opposes the effect of dopamine. They are useful against tremor and stiffness. Their use is limited by their high rate of side effects. The most commonly used anticholinergic medications are trihexyphenidyl (Artane®) and benztropine (Cogentin®). Ethopropazine (Parsitan®) is available in Canada.
- Amantadine: also known as Symmetrel® can relieve the motor symptoms of PD, particularly tremor. It has a more significant effect in reducing the abnormal movements (dyskinesias) caused by chronic dopaminergic treatment
Other agents: medications to treat depression and anxiety, constipation, urinary and erectile dysfunction, and sleep disturbances may be necessary to optimize quality of life for people living with PD.
- Other agents: medications to treat depression and anxiety, constipation, urinary and erectile dysfunction, and sleep disturbances may be necessary to optimize quality of life for people living with PD.