Medications 

Levodopa is the most effective and most prescribed medication for Parkinson’s. It helps with motor symptoms like stiffness, slowness, and tremors by restoring dopamine in the brain. Carbidopa or benserazide is combined with levodopa to enable more levodopa to reach the brain rather than remain in the bloodstream. The most common formulation of levodopa are tablets or capsules that are usually taken three or more times per day. Levodopa can be used in conjunction with other Parkinson’s medications to address the same symptoms. Common side effects of levodopa include nausea and light-headedness. Infusion therapies aim to provide steady symptom relief throughout the day. 

Tablet Formulations

Capsule Formulations

Infusion Formulations

Dopamine agonists help manage Parkinson’s symptoms like slowness, stiffness, and tremors and are considered the second-most effective medication category for motor symptoms after levodopa. They can be used alone or with other medications to address motor symptoms. Over years of use, dopamine agonists are less likely than levodopa to cause dyskinesias or motor fluctuations. Common side effects include nausea, and dizziness. Other possible side effects include leg swelling, sleep attacks, and compulsive behaviours. They are best taken with food to reduce stomach upset. 

MAO-B inhibitors help treat Parkinson’s by preventing dopamine breakdown, making more of it available to improve movement symptoms like slowness, stiffness, and tremors. They can be used on their own as initial treatment for very mild symptoms or as supplemental medications to reduce off time as Parkinson’s progresses. Common side effects include nausea and light-headedness. Because MAO-B inhibitors increase and prolong the effects of dopamine, the side effects of dopamine may also be enhanced, including dyskinesia.

There are multiple medications that are contraindicated with MAO-B inhibitors. See the Medications to use with caution table below for more information.

COMT inhibitors increase and prolong levodopa’s effects. COMT inhibitors have no effect on their own and are always used in conjunction with levodopa. COMT inhibitors are used primarily to treat motor fluctuations and reduce OFF time. Since they work by amplifying levodopa’s impact, they can also increase its side effects, including dyskinesia. 

Amantadine is mainly used to help reduce involuntary movements (dyskinesias) in people with Parkinson’s, after adjusting levodopa and other Parkinson’s medications. Common side effects include nausea, dizziness, constipation, and urinary retention while others, like confusion in older adults, leg swelling, and a skin rash called livedo reticularis, can also occur. 

Anticholinergic medications help manage tremors and dystonia in Parkinson’s by reducing acetylcholine, a neurotransmitter that interacts with dopamine. Their use is limited in Canada due to significant side effects. They may be considered for younger people in early stages of Parkinson’s and with prominent tremor. They are not recommended in older adults with Parkinson’s because they can increase confusion, cognitive slowing, and hallucinations. Other possible side effects include dry mouth, worsening of glaucoma, blurry vision, constipation and urinary retention. 

SNRIs are antidepressants that help manage depression, anxiety, and OCD. They can also be helpful for treating nerve pain. It typically takes four to six weeks at a therapeutic dose to show effects. They can raise blood pressure and may cause side effects like headache, nausea, dizziness, and sexual dysfunction. SNRIs should be used with caution in conjunction with other serotonergic medications due to a potential for serotonin syndrome. 

SSRIs are the most prescribed antidepressants for Parkinson’s-related depression because of their tolerability. These medications can also be used to treat anxiety and obsessive-compulsive disorder (OCD). It often takes four to six weeks of a therapeutic dose for full effect. They may be combined with other antidepressants but doing so requires caution due to the risk of serotonin syndrome. Potential side effects include headaches, nausea, insomnia, nightmares (if taken at night), jitteriness, sexual dysfunction, low sodium levels, and weight gain. 

TCAs are antidepressants used for depression, anxiety, and OCD. They can also be helpful for treating nerve pain. TCAs are prescribed less often than SSRIs and SNRIs due to a higher likelihood of side effects. Possible side effects include dry mouth, constipation, orthostatic hypotension, urinary retention, and confusion. People with heart conditions (such as arrhythmia or QTc prolongation) should exercise caution when using TCAs. These medications should be used with caution in conjunction with other serotonergic medications due to the potential for serotonin syndrome. 

These medications can also have benefits for depression, anxiety, and OCD. Like SSRIs, SNRIs, and TCAs, they often take four to six weeks of a therapeutic dose to take effect. Some of these medications should be used with caution in conjunction with serotonergic medications due to the potential for serotonin syndrome. 

Constipation is a common non-motor symptom of Parkinson’s that can significantly impact daily life, and treatment often starts with lifestyle changes like drinking more water, eating fiber-rich foods, and staying active. Consulting a doctor to review supplements and medications, as well as considering over-the-counter options, can also help manage symptoms effectively. 

Excessive drooling (sialorrhea) is a common non-motor symptom in later stages of Parkinson’s. Certain medications, used either on- and off-label, can help manage it. While side effects depend on the treatment, the most frequent side effect is dry mouth. 

Fatigue is a common symptom in Parkinson’s that often overlaps with sleepiness and/or depression, making treatment for those conditions crucial. While some medications may offer stimulant benefits, lifestyle changes – such as reserving energy, staying active, eating well, staying hydrated, getting enough sleep, and taking breaks when needed – are key to managing fatigue symptoms. Medication side effects like headaches, dizziness, and anxiety should be considered. 

Overactive bladder (OAB) refers to urinary urgency and/or frequency. The bladder is a muscle, and spasms of the bladder muscle can cause urinary urgency and/ or frequency among people with Parkinson’s. Managing OAB may involve reducing alcohol and caffeine intake, limiting fluids at night, strengthening the pelvic floor with Kegel exercises, or using medications to reduce bladder spasms. Possible medication side effects include constipation, dry mouth, blurry vision, mental confusion (in older people with dementia), and urinary retention. Most OAB medications work via anticholinergic effects, and they can have the side effects of anticholinergic medications. 

Dementia in advanced Parkinson’s affects thinking, memory, and daily independence. It is often managed with cholinesterase inhibitors, which increases acetylcholine to support cognitive function and may also help reduce freezing of gait. Note that anticholinergic medications have the opposite effect (they lower acetylcholine), so anticholinergic medications should usually be avoided by a person with Parkinson’s-related dementia. Possible side effects include nausea with poor appetite and weight loss, diarrhea, dizziness with slow heart rate, and tremor. 

Neurogenic orthostatic hypotension (nOH) is a common symptom of Parkinson’s, characterized by a sudden drop in blood pressure upon standing, which can lead to dizziness and imbalance. While medications can help manage nOH in people with Parkinson’s, simple lifestyle adjustments, such as increasing fluid, salt, and caffeine intake, wearing compression garments, and elevating the head of the bed, can be highly effective as well. Possible side effects of medications include high blood pressure when lying down (supine hypertension).  

Dementia in advanced Parkinson’s affects thinking, memory, and daily independence, often managed with cholinesterase inhibitors, which boost acetylcholine to support cognitive function and may also help reduce freezing of gait. However, anticholinergic medications can worsen symptoms and should generally be avoided, while side effects of dementia treatments can include nausea, weight loss, diarrhea, dizziness, and tremors. 

Hallucinations involve perceiving sights or sounds that do not exist. Delusions are firmly held false thoughts, worries or beliefs. Both of these fall under the umbrella of psychosis and vary in severity. Medications used to treat psychosis can cause drowsiness, low blood pressure, and constipation, requiring careful monitoring and individualized treatment. 

Changes in sexual function and desire can be part of Parkinson’s itself or side effects of medications, particularly antidepressants. Treatments like erectile dysfunction medications and lubricants can help, but lifestyle adjustments and alternative therapies are often most effective. Hypersexuality and compulsive sexual behaviour are side effects of dopamine agonists and can often be treated by reducing dosage. 

Sleep disturbances are common in Parkinson’s, ranging from insomnia and restless leg syndrome to daytime sleepiness and REM sleep behavior disorder (RBD). While medications can help, an integrated approach combining lifestyle adjustments and medical treatment is often most effective, and a thorough assessment is crucial to address underlying causes and medication-related contributors.