Which Kind of Drug is Forbidden to Use in Parkinson's Disease?

October 10, 2025 •

4 min read

According to studies, an alarming number of hospitalized Parkinson's disease patients are prescribed contraindicated drugs that can significantly worsen motor symptoms. For individuals with this condition, knowing which kind of drug is forbidden to use in Parkinson's disease is critical to avoiding potentially dangerous medication errors and protecting their quality of life.

Quick Summary

Certain medications are forbidden or cautioned against in Parkinson's disease because they interfere with dopamine, worsening motor symptoms, or cause dangerous interactions with standard treatments. Key culprits include dopamine-blocking agents, some antidepressants, and specific anti-nausea drugs.

Key Points

Dopamine-blocking drugs are forbidden: Typical antipsychotics like haloperidol and certain antiemetics like metoclopramide block dopamine receptors and must be avoided as they worsen PD symptoms.
Risky drug interactions are common: MAO-B inhibitors used for PD can have dangerous interactions with specific narcotics (meperidine, tramadol), decongestants, and some antidepressants.
Not all antipsychotics are equal: While most antipsychotics should be avoided, atypical options like clozapine and quetiapine are sometimes used cautiously for PD-related psychosis, under specialist supervision.
Carefully check over-the-counter meds: Cold, allergy, and cough medicines containing decongestants (e.g., pseudoephedrine) or dextromethorphan can interact dangerously with PD medications.
Review all medications with a doctor: Periodically reviewing a complete list of medications and supplements with a neurologist or specialist is essential to prevent unintended drug interactions.
Alternative options exist for most needs: Safer drug alternatives, such as ondansetron for nausea, are available to manage common conditions without exacerbating PD symptoms.

For individuals managing Parkinson's disease (PD), medication is the cornerstone of treatment, primarily focused on replacing or mimicking the effects of the neurotransmitter dopamine. However, the effectiveness of these therapies can be severely undermined by taking other medications that interfere with dopamine. A number of drug classes are considered forbidden or must be used with extreme caution due to their potential to worsen motor symptoms or cause life-threatening drug interactions. Understanding these risks is crucial for both patients and their caregivers to ensure proper medical management.

The Most Dangerous: Dopamine-Blocking Antagonists

The most significant class of drugs to avoid are those that block dopamine receptors in the brain. Since PD symptoms are caused by a dopamine deficiency, blocking the remaining dopamine counteracts the effects of PD medication and drastically worsens tremors, rigidity, and bradykinesia (slowness of movement).

Typical (First-Generation) Antipsychotics

These medications are prescribed to treat conditions like schizophrenia and psychosis. They have a high potency for blocking dopamine D2 receptors and are absolutely contraindicated in PD patients. Examples include:

Haloperidol (Haldol)
Chlorpromazine (Thorazine)
Perphenazine (Trilafon)
Fluphenazine (Prolixin)
Thioridazine (Mellaril)
Pimozide (Orap)

Antiemetics (Anti-Nausea Drugs)

Many common anti-nausea medications work by blocking dopamine receptors and must be avoided. The consequences can be a severe worsening of motor symptoms, and unfortunately, these are sometimes prescribed inappropriately in hospital settings. Safe alternatives, such as ondansetron, are available. High-risk antiemetics to avoid include:

Metoclopramide (Reglan)
Prochlorperazine (Compazine)
Promethazine (Phenergan)

Atypical (Second-Generation) Antipsychotics

While generally less potent than their typical counterparts, several atypical antipsychotics also have significant dopamine-blocking effects and should be avoided or used only with extreme caution. Risperidone and olanzapine, in particular, can cause significant extrapyramidal symptoms. Safer atypical options are available for PD-related psychosis.

Risky Interactions with MAO-B Inhibitors

Monoamine oxidase B (MAO-B) inhibitors like selegiline, rasagiline, and safinamide are a key part of PD treatment, as they increase dopamine levels by blocking its breakdown. However, combining them with certain other drugs can lead to serious, and potentially fatal, interactions, such as hypertensive crisis (dangerously high blood pressure) or serotonin syndrome (excessive serotonin activity).

Narcotics and Analgesics

Specific narcotic pain relievers can cause serious interactions, especially with MAO-B inhibitors, leading to serotonin syndrome. These include:

Meperidine (Demerol)
Tramadol (Ultram)
Methadone (Dolophine)

Certain Antidepressants

Most nonselective MAO inhibitors, a type of antidepressant, are absolutely contraindicated for patients taking levodopa due to the risk of hypertensive crisis. Selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) can sometimes be used cautiously, but their combination with MAO-B inhibitors carries a risk of serotonin syndrome. High-risk antidepressants include:

Nonselective MAOIs (e.g., phenelzine, tranylcypromine)
St. John's Wort (herbal supplement)

Cold and Allergy Medications

Some over-the-counter cold and allergy products contain stimulants or decongestants that can interact with MAO-B inhibitors. Active ingredients to carefully check for and avoid include:

Ephedrine
Pseudoephedrine
Phenylephrine
Dextromethorphan (a cough suppressant)

Other Medications to Avoid or Use with Caution

Antihypertensives

Some blood pressure medications can deplete dopamine stores or interfere with levodopa's effectiveness, worsening PD symptoms. Examples include reserpine and methyldopa.

Muscle Relaxants

Cyclobenzaprine (Flexeril) can interact negatively with MAO-B inhibitors.

Table: Dopamine-Blocking Drugs vs. Safer Alternatives


Medication Class	Forbidden or High-Risk Options	Safer Alternative Options
Typical Antipsychotics	Haloperidol, Chlorpromazine, Perphenazine	- (Generally not recommended)
Antiemetics	Metoclopramide (Reglan), Prochlorperazine (Compazine), Promethazine (Phenergan)	Ondansetron (Zofran), Domperidone (outside US)
Atypical Antipsychotics	Risperidone (Risperdal), Olanzapine (Zyprexa), Aripiprazole (Abilify)	Clozapine (Clozaril), Quetiapine (Seroquel), Pimavanserin (Nuplazid)
Pain Medication	Meperidine, Tramadol	Safe alternatives as advised by a doctor

Conclusion

Knowing which kind of drug is forbidden to use in Parkinson's disease is a critical aspect of managing the condition and preventing serious health complications. The most dangerous medications are those that block dopamine receptors, directly sabotaging the brain's already-compromised dopaminergic system. This includes typical antipsychotics and several common anti-nausea medications. Additionally, dangerous interactions with MAO-B inhibitors can arise from combining them with certain narcotics, antidepressants, or decongestants. Always consult a neurologist or PD specialist before taking any new medication, including over-the-counter drugs and supplements, to ensure patient safety and optimize the treatment plan. It is also important to inform all healthcare providers, especially in a hospital setting, of a Parkinson's diagnosis to prevent the inadvertent prescription of a contraindicated drug.

Parkinson's Foundation: Medications to Avoid

Medications and Parkinson's Disease

It is imperative for individuals with Parkinson's to be their own advocates in healthcare settings. Carrying a list of all medications and a pre-made list of contraindicated drugs can prevent errors during emergencies or hospital stays. When in doubt, always request a consultation with a neurologist before any new prescription or treatment is started.

Frequently Asked Questions

You should avoid anti-nausea medications that block dopamine receptors, such as metoclopramide (Reglan), prochlorperazine (Compazine), and promethazine (Phenergan). Safer alternatives like ondansetron (Zofran) are often used instead.

Typical (first-generation) antipsychotics, like haloperidol, should be avoided completely. Some atypical antipsychotics, such as clozapine and quetiapine, may be used for psychosis associated with PD, but only under the close supervision of a specialist.

Not all antidepressants are unsafe, but certain classes carry risks. Nonselective monoamine oxidase inhibitors (MAOIs) are contraindicated, and some antidepressants, especially when combined with PD-specific MAO-B inhibitors, can increase the risk of serotonin syndrome.

It is crucial to read labels carefully. Many cold and allergy medications contain decongestants like pseudoephedrine or phenylephrine, which can interact with PD medications, particularly MAO-B inhibitors. Always consult your neurologist or pharmacist before taking new over-the-counter products.

Pain relievers like meperidine (Demerol) and tramadol (Ultram) can cause a serious and life-threatening reaction called serotonin syndrome when combined with MAO-B inhibitors used for PD. Always inform your doctor of your PD medication regimen before starting a new painkiller.

Some older blood pressure medications, like reserpine and methyldopa, can deplete dopamine stores in the brain, thereby worsening Parkinson's motor symptoms. Numerous safer alternatives are available.

Some muscle relaxants, such as cyclobenzaprine (Flexeril), can interact negatively with MAO-B inhibitors. Safer options for managing muscle spasms related to PD should be discussed with a healthcare provider.

Inform hospital staff and your medical team immediately that you have Parkinson's disease and that the prescribed drug is contraindicated. You or a family member should be prepared to advocate for appropriate alternative medications, and carrying a list of forbidden drugs can be helpful.