5.10 Antiparkinson Medications V2

Parkinson’s disease is believed to be related to an imbalance of dopamine and acetylcholine and a deficiency of dopamine in certain areas of the brain, particularly the substantia nigra. Drug therapies are aimed at increasing levels of dopamine and/or antagonizing the effects of acetylcholine. Drug therapy does not cure the disease but is used to slow the progression of symptoms (Lilley, Collins & Snyder, 2021).

There are six different pharmacological classes of medications that are commonly used to treat the motor symptoms of Parkinson’s Disease (PD). The choice of which medications will depend on factors such as the client’s age, comorbidities, functional impairment, severity of symptoms, client employment and client preference (Parkinson Canada, n.d.). Many are used as adjunct therapy in conjunction with levodopa.

Click on the link to learn more about Parkinson’s Disease, including the mechanism of action of many of the drugs. Pharmacology – Drugs for Parkinson’s Disease (made easy).    https://www.youtube.com/watch?v=Z84iypHdftQ

Improving Outcomes with Parkinson’s Disease Medications:

• Any of the medications need to be taken on time, every time. This is crucial for effectively managing the symptoms.  For example, by taking meds on time will avoid motor fluctuations and will help maintain dopamine levels throughout the day. Further, early and regular medication supports the remaining dopaminergic receptors in the brain.
• Have client keep a medication/mobility diary tor record when they take their meds and when they experience adverse effects to best know if dosage and med is right for the client.
• Encourage blister packs, pill boxes or pill dispensers to ensure medications are taken on time.
• For dopaminergic meds, take 30-60 minutes before a meal high in protein to avoid delayed onset of action.
• Avoid alcohol or other CNS meds (anticholinergic agents, antidepressants, benzodiazepines) to avoid combined effects of dizziness, fatigue and drowsiness.

Common non-motor symptoms of PD and treatment:

• Constipation: can develop years before motor symptoms are evident. Slow transit time can impact intestinal absorption of dopaminergic meds. Treat with high fiber diet, more fluids, physical activity and meds such as polyethylene glycol or psyllium.
• Depression and anxiety: up to 50% of persons with PD; antidepressants such as SSRIs, SNRIs or other agents such as Bupropion.
• Pain: PD reduces pain thresholds as well as morning dystonia and muscle pain/stiffness. Treat with acetaminophen, duloxetine or gabapentin along with non-pharmacological interventions.
• Sialorrhea (drooling): PD clients have difficulty swallowing saliva in up to 78% of cases. Glycopyrrolate and atropine are two meds that may provide relief.
• Nausea: domperidone is effective.

(Parkinsons Canada (n.d.); Parkinson’s Australia, 2026).

https://www.parkinsons.org.au/information-hub/parkinsons-medications/

In this unit, we will explore the common medications used to treat Parkinson’s Disease:  carbidopa/levodopa, selegiline, and amantadine

Carbidopa/Levodopa

Carbidopa/levodopa is the most common drug used to treat Parkinson’s disease and is usually started as soon as the client becomes functionally impaired.

Mechanism of Action

Administration of dopamine is ineffective in the treatment of Parkinson’s disease because it does not cross the blood brain barrier. But levodopa, the metabolic precursor of dopamine, does cross the blood-brain barrier and is converted to dopamine in the brain. Dopa decarboxylase inhibitor or DDI (Carbidopa) is combined with levodopa to help stop the breakdown of levodopa before it is able to cross the blood-brain barrier. Carbidopa serves another purpose, it decreases levodopa-induced nausea and vomiting that is common with levodopa alone.

Indications for Use

Carbidopa/levodopa is indicated for Parkinson’s disease. It improves muscle rigidity, bradydyskinesia and tremor in clients. It is also used to treat restless leg syndrome, to treat Parkinson-like symptoms that can develop after encephalitis or injury to the nervous system due to carbon monoxide poisoning or manganese poisoning (MedlinePlus, 2026).

Nursing Considerations

Administration:

• Oral administration, immediate release, disintegrating tablets, and extended-release. Taken 3-4 times per day. Do not crush or chew extended-release tablets. Suspension formula available for continuous administration via nasogastric or PEG tube.
• Example of dose: levodopa/carbidopa controlled-release 200/50 mg. Gradual absorption over 4-5 hours, but majority within 2-3 hours (PharmScience, 2020).
• Inhalation formulas are available and used as an adjunct therapy with oral dosages.
• Take oral form with meals to decrease GI upset. To improve absorption, take 1 hour before or 2 hours after meals that contain protein. High fat, high protein meals will delay absorption by 2 hours and overall decrease amount absorbed (competes with amino acid transporters) (Gandhi & Saadabadi, 2023).

Dosages gradually increased depending on effect.  5 days to reach steady state, and a few months to see full benefit.

Avoid in clients with peptic ulcer disease (risk of GI bleed). Extra caution with client with cardiac conditions(atrial nodal or ventricular arrhythmias). Caution with clients with peripheral neuropathy or history of psychosis.

Pregnancy: levodopa does cross the placenta and can potentially harm the fetus, although insufficient information is available. Caution with breastfeeding as it is excreted in breast milk.

Carbidopa/Levodopa is recommended for use in clients older than age 18.

Monitoring:

• Assess for a change in motor symptoms.
• Assess for change in mental health such as hallucinations, psychotic behaviour, confusion or excessive dreaming.
• Assess for depression and risk of suicidality.
• Monitor BUN, creatinine levels and hepatic function regularly.
• Clients with glaucoma, test intraocular pressure as it can increase intraocular pressure.
• Assess peripheral neuropathy before treatment and periodically while on med.
• Monitor for melanoma – increased incidence but not clear if from meds or PD itself.

Drug Interactions:

• Contraindicated for use with MAOIs (risk of hypertensive crisis). Ensure a 14-day washout period when switching from levodopa to an MAOI or vice versa.
• Antipsychotics, antihypertensives, iron, isoniazid and metoclopramide
• Patients taking D2 antagonists may see a reduction in the effects of levodopa, and as a result, it may reduce the beneficial effects of the drug.

Clients taking carbidopa and levodopa have reported suddenly falling asleep without prior warning of sleepiness while engaged in activities of daily living (including operation of motor vehicles). Clients should be advised to exercise caution while driving or operating machines during treatment with carbidopa and levodopa (McCuistion et al, 2019).

Surgery: if going for surgery, hold the dose on the day of surgery and resume once client able to swallow. Check orders and consult with physician.

Do not abruptly discontinue med: risk of symptoms of neuroleptic malignant syndrome (NMS) have been reported with dose reductions or withdrawal of certain antiparkinsonian agents. Observe clients carefully when the dosage of levodopa is reduced abruptly or discontinued.

(Gandhi & Saadabadi, 2023; Lilley et al, 2020).

Adverse/Side Effects

Most common side effects:

• nausea, dizziness, headache, and somnolence. To relieve nausea, a higher dose of carbidopa may help. Or, adding domperidone can be helpful if additional carbidopa is ineffective.
• Dyskinesia is common, which may require dosage reduction.
• CV: dizziness and postural hypotension; thus, reducing or discontinuing antihypertensive medications is required for some clients.

Older adults: higher risk of confusion, hallucinations, delusions, psychosis and agitation.  Higher risk of hip fractures due to mild increase in homocysteine levels.

Adverse Effects:

Hallucinations and psychotic-like behavior have been reported with dopaminergic medications. Clients taking dopaminergic medications may experience intense gambling urges, increased sexual urges, intense urges to spend money or indulge in binge eating, and/or other intense urges, and the inability to control these urges. These urges stop when the dosage is decreased or the medication is discontinued.

Melanoma: A higher risk for melanoma has been reported. Assess skin regularly.

Occasionally, dark red, brown, or black color may appear in saliva, urine, or sweat after ingestion of carbidopa and levodopa. Although the color appears to be clinically insignificant, garments may become discolored (Lilley et al, 2020; McCuistion et al, 2018).

Client Teaching

• See Improving Outcomes with Parkinson’s Disease Medications at the beginning of this unit.
• Clients should take their medications at regular intervals as directed.  If gastric irritation is experienced, clients may eat food shortly after taking medications but high-protein foods may impair drug action.
• Clients should be instructed to plan their meal times around medication times to improve their ability to use their utensils.
• Medications may cause increased drowsiness, dizziness, and orthostatic changes. To prevent falls, ambulate slowly and use assistance as needed (cane, walker).
• Clients should carefully assess their skin to monitor for new lesions and any abnormality should be reported to the healthcare provider.

Carbidopa/levodopa Medication Card

Now let’s take a closer look at the medication card for carbidopa-levodopa. Medication cards like this are intended to assist students to learn key points about each medication. Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication. Basic information related to each class of medication is outlined below.

Downloadable file (.docx): Carbidopa:levodopa Medication Card

Selegiline

Selegiline is often used in conjunction with carbidopa-levodopa when clients demonstrate a deteriorating response to this treatment. It is helpful to control symptom fluctuations (Lilley et al, 2020). The other MAO inhibitor, rasagiline, is also prescribed.

Mechanism of Action

Selegiline acts as a selective, irreversible MAO inhibitor, blocking the breakdown of dopamine. This leads to an increased concentration of dopamine that is ready to use in the nerve cells (Parkinsons Canada, n.d.). The MAO enzymes are responsible for catabolizing neurotransmitters such as norepinephrine, serotonin and dopamine. The blocking of these enzymes will inhibit reuptake these neurotransmitters in the CNS and elevate monoamines at the synaptic cleft.

Use for Parkinson’s Disease: at lower doses, selegiline selectively inhibits monoamine oxidase-B (MAO-B).

Use for major depressive disorder: at higher doses, selegiline inhibits both MAO-A and MAO-B.

The mechanism of action of this med is not entirely understood. There is evidence selegiline may slow the progression of Parkinson disease by promoting the production of neurotrophins such as brain-derived neurotrophic factor, nerve growth factor, and glial cell line-derived neurotrophic factor (Moore & Saadabadi, 2023). For PD, the benefits of selegiline is it can prolong the effects of levodopa and decrease the fluctuations in motor control. These benefits are usually only for 12 to 24 months, before it is no longer effective (Rosenjack Burchum & Rosenthal, 2019).

Indications for Use

Selegiline is indicated as an adjunct in the management of Parkinsonian clients being treated with levodopa/carbidopa who exhibit deterioration in the quality of their response to this therapy. It is usually used as adjunct therapy but it can be used for early PD to control motor symptoms. It is also used as adjunct therapy for major depression disorder and off label for attention-deficit hyperactivity disorder (Moore & Saadabadi, 2023).

Nursing Considerations

Administration: oral or transdermal.  Both available in different dosages and titrated to effect.

• Oral route given by capsule or oral disintegrating tablet BID.
• Transdermal route: higher plasma concentration resulting in the desired nonselective MAO inhibition and anti-depressive effect to treat MDDs. Apply patch every 24 hours to clean dry skin to outer surface of the upper arm, upper torso or upper thighs. Do not cut the patch (Moore & Saadabadi, 2023).

Caution with renal insufficiency or hepatic disease. Not recommended for severe hepatic disease or end-stage renal disease.

Pregnancy and Lactation: There is a lack of data regarding the potential fetal harm with maternal use during pregnancy or breastfeeding.  Safety has not been established in children.

Large doses of selegiline may inhibit MAO-A that promotes the metabolism of tyramine in the GI tract, which can cause a hypertensive crisis. At lower doses, selegiline is selective to MAO-B, but caution is still advised.

Sudden discontinuation can lead to parkinsonism and antidepressant discontinuation syndromes. Dosing needs be tapered before discontinuation.

Prior to elective surgery: Selegiline use within 14 days before elective surgery is contraindicated due to its adverse effects on blood pressure.

Adverse/Side Effects

High Alert Med: Side effects are dose-dependent, with larger doses posing a hypertensive crisis risk in conjunction with the consumption of food or beverages with tyramine. Higher doses can increase the risk for hypertensive crises. For lower doses, no specific restrictions except to avoid aged cheese over 150mg/day (Parkinsons Canada, n.d.).

Foods high in tyramine include: aged cheese, pickled foods, cured meat, smoked or processed meat, soybeans, dried fruits, soy sauce, homebrewed beer and red wine.

Common side effects:

This med is usually well tolerated.

• Anticholinergic effects: dry mouth and constipation.
• Insomnia is very common. Minimize insomnia by taking last dose at noon.
• Headaches, dizziness, insomnia, nausea and weight loss.
• Dyskinesia

Adverse effects:

• Orthostatic hypotension: encourage client to ambulate slowly. Report symptoms of dizziness.
• Mental health changes: hallucinations, any change in mental status.

Client Teaching

• See Improving Outcomes with Parkinson’s Disease Medications at the beginning of this unit.
• Depending on the dose, clients should be advised to avoid foods high in tyramine. If on a low dose and as advised by their prescriber, avoid only aged cheese >150 mg/day. Monitor blood pressure if eating tyramine rich foods.
• Inform client that they may experience drowsiness, dizziness, and blood pressure changes when ambulating. Caution with changing positions, and ambulating.
• Monitor blood pressure regularly to reduce risk of falls from hypotension and to be aware of high blood pressure leading to hypertensive crisis.
• May experience abnormal behaviors such as hallucination, sexual urges, gambling, etc., this should be reported promptly to the healthcare provider.
• Monitor for any change in motor symptoms and other effects of PD. Notify prescriber of these changes.
• Transdermal application: change patch every 24 hours. Do not cut the patch. Skin irritation may occur.

(Moore & Saadabadi, 2023; Parkinsons Canada, n.d.)

Selegiline Medication Card

Now let’s take a closer look at the medication card for selegiline.

Downloadable file (.docx): Selegiline Medication Card

Amantadine

Amantadine is used in the early stages of Parkinson’s disease but can be effective in moderate or advanced stages in reducing tremor and muscle rigidity (Lilley et al, 2020). It was developed as an anti-viral for influenza A, but found to be effective in treating the motor symptoms of Parkinson’s disease. It is no longer used as an antiviral against influenza A due to resistance

Mechanism of Action

The exact mechanism of action is unknown. Amantadine has an effect on many receptors. It inhibits dopamine uptake, stimulates dopamine release, weakly antagonizes N-methyl-D-aspartate receptors and may have an effect on cholinergic receptors (Chang & Ramphul, 2023; Rosenjack Burchum & Rosenthal, 2019).  As an antiviral, it interferes with viral replication.

Indications for Use

Amantadine is used for Parkinson’s disease, to reduce the bradykinesia, rigidity and tremor symptoms. It is used as adjunct therapy with levodopa to create a synergistic effect (Chang & Ramphul, 2023).  Amantadine is also used for other purposes, including first-line treatment for fatigue in multiple sclerosis. There is also some benefit for clients with restless leg syndrome and to improve function in traumatic brain injuries.

Nursing Considerations

Oral administration. Either once daily or BID, with tapering up the dose based on effect.

Monitor: prior to starting on the medication and during treatment:

• Labs: renal function and liver function tests. Assess for elevated creatinine and BUN. Assess for increase in AST and ALT.
• Mental status: assess mental status before therapy and then during therapy for a change in status. Risk for hallucinations, delusions, depression, suicidality.

• Blood pressure: baseline BP prior to therapy, assess for orthostatic hypotension (lying, sitting and standing BP).

Renal impairment or older adult: cautious use, anticipate a reduced dose. Monitor creatine clearance as amantadine is excreted via the kidney.

Caution with cardiac disease, glaucoma and prostrate hypertrophy.

Do not abruptly discontinue: risk of Neuroleptic Malignant Syndrome (NMS) with dose reduction or withdrawal of amantadine therapy.  Symptoms include high fever, tachycardia, muscle rigidity, and altered mental status.  When discontinuing, dose will be reduced by half for one week, then discontinued (Chang & Ramphul, 2023).

Older adult: dose should be decreased if renal insufficiency. The older adult is more at risk for anti-cholinergic effects, so monitor for dizziness to avoid falls. Higher risk of hallucinations so assess mental health status.  Higher risk of edema in lower extremities (Parkinsons Canada, n.d.).

Pregnancy: contraindicated due to risk of Teratogenic effects on the fetus.

Adverse/Side Effects

Common side effects:

• Anticholinergic effects: dry mouth, constipation, urinary retention, confusion, blurred vision.
• CV: orthostatic hypotension, syncope, peripheral edema, dizziness. Insomnia if taken later in the day.
• Neuro: confusion, hallucinations
• Livedo reticularis is a less common side effect, causing red-purple discoloration of the skin. Can occur after on the med for over one month. This is reversible when the med is discontinued.

Adverse Effects:

• Neuroleptic malignant syndrome if abruptly discontinued.
• Risk of psychosis: This drug can cause intense gambling urges, increased sexual urges, intense urges to spend money uncontrollably, and other intense urges with an inability to control them.
• Risk of suicidal ideation and CNS depression. Monitor mental health and assess for suicidality.

(Chang & Ramphul, 2023; Parkinsons Canada, n.d.

Client Teaching

• Clients should take medications as directed and ensure they do not skip or double doses.
• Medications may cause drowsiness, dizziness, and orthostatic blood pressure changes. Monitor blood pressure and to care with ambulation or position changes.
• Clients should avoid using this medication with OTC cold medications or alcoholic beverages due to potential increased risk of dizziness or confusion.
• If clients, family, or caregivers note worsening depression or suicidality, this should be reported immediately to the healthcare provider.

Amantadine Medication Card

Now let’s take a closer look at the medication card for amantadine. Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication.

Downloadable file (.docx): Amantadine Medication Card

References:

Chang, C. & Ramphul, K. (2023). Amantadine. National Library of Medicine. StatPearls. Amantadine – StatPearls – NCBI Bookshelf

Gandhi, K. & Saadabadi, A. (2023). Levodopa (L-dopa). National Library of Medicine. Levodopa (L-Dopa) – StatPearls – NCBI Bookshelf

Lilley, L., Collins, S., & Snyder, J. (2020). Pharmacology and the Nursing Process. pp. 246-272. Elsevier. ↵

MedlinePlus (2026). Levodopa and Carbidopa. National Library of Medicine.  Levodopa and Carbidopa: MedlinePlus Drug Information

McCuistion, L., Vuljoin-DiMaggio, K., Winton, M, & Yeager, J. (2018). Pharmacology: A patient-centered nursing process approach. pp. 227-305. Elsevier. ↵

Moor, J. & Saadabadi, A. (2023). Selegiline. National Library of Medicine. StatPearls. Selegiline – StatPearls – NCBI Bookshelf

Parkinson’s Australia (2026). Parkinson’s medications. Parkinson’s medications – Parkinson’s Australia

Parkinsons Canada (n.d.). Medications to treat Parkinson’s Disease.  Parkinson Canada | Home

PharmaScience (2020). Levodopa-Carbidopa Controlled Release. Product Monograph. PharmaScience Inc.

Rosenjack Burchum, J., & Rosenthal, L. (2019). Lehne’s pharmacology for nursing care (10th ed.). Elsevier: Canada