Medications: What medications are bad for Parkinson's?

October 10, 2025 •

4 min read

According to research, 8–12% of cases of parkinsonism are caused by medication, with certain drug classes posing significant risks for people with Parkinson's disease (PD). Knowing what medications are bad for Parkinson's is crucial for managing symptoms effectively and preventing complications.

Quick Summary

Certain medications can aggravate motor symptoms in people with Parkinson's disease by blocking dopamine receptors in the brain. This includes typical and atypical antipsychotics, some anti-nausea drugs, and specific blood pressure medications, which can lead to drug-induced parkinsonism or worsen existing PD.

Key Points

Dopamine-Blocking Drugs: Medications that block dopamine receptors, including many antipsychotics and anti-nausea drugs, are generally harmful for people with Parkinson's and can worsen motor symptoms.
First-Generation Antipsychotics: 'Typical' antipsychotics like haloperidol and chlorpromazine are potent dopamine blockers and are particularly high-risk for causing drug-induced parkinsonism.
Certain Antiemetics: Common anti-nausea drugs such as metoclopramide (Reglan) and prochlorperazine (Compazine) should be avoided because they counteract the effects of PD medications.
Specific Pain Medications: The narcotic meperidine (Demerol) must be avoided in patients taking MAO-B inhibitors (e.g., selegiline, rasagiline) due to the risk of serotonin syndrome.
Over-the-Counter Risks: Some cold and flu remedies containing decongestants or stimulants can interfere with PD medications and should be checked with a pharmacist before use.
Crucial Communication with Doctors: Always inform all healthcare providers of your Parkinson's diagnosis to ensure they do not prescribe contraindicated medications.

How Certain Medications Can Worsen Parkinson's Symptoms

For individuals with Parkinson's disease (PD), managing symptoms involves careful coordination with healthcare professionals. The key to successful treatment lies in balancing therapies that increase dopamine levels in the brain, such as levodopa, while avoiding drugs that interfere with this delicate system. Medications that block dopamine receptors can counteract the effects of PD therapy and lead to drug-induced parkinsonism (DIP), which can manifest as tremors, slowness, and rigidity. The elderly are at a higher risk of DIP due to decreased dopamine in the brain and potential exposure to multiple medications. It is important to note that some people may have underlying, undiagnosed PD that is unmasked or worsened by taking certain drugs.

Antipsychotic Medications

Antipsychotics, particularly first-generation or 'typical' antipsychotics, are some of the most common causes of DIP because they are potent blockers of dopamine D2 receptors. Even some second-generation or 'atypical' antipsychotics, while less likely to cause motor side effects, can still worsen PD symptoms. People with PD-related psychosis require specialized treatment with drugs that do not significantly block dopamine.

Typical Antipsychotics: These drugs carry a high risk of aggravating PD symptoms. Examples include: haloperidol (Haldol), chlorpromazine (Thorazine), and fluphenazine (Modecate).
Atypical Antipsychotics: While often safer, certain atypical antipsychotics should still be avoided. Risperidone (Risperdal) and olanzapine (Zyprexa) are known to worsen motor symptoms. Pimavanserin (Nuplazid) is specifically approved for PD-associated psychosis and works on serotonin, not dopamine, reducing the risk of motor side effects.

Antiemetics (Anti-Nausea Drugs)

Many anti-nausea medications work by blocking dopamine receptors, making them unsuitable for people with Parkinson's. This class of drugs should be used with extreme caution or avoided entirely unless prescribed by a specialist aware of the PD diagnosis.

Metoclopramide (Reglan): A very common cause of drug-induced movement disorders. It is a potent D2 receptor blocker and should be avoided.
Prochlorperazine (Compazine): Another antiemetic that blocks dopamine receptors and can worsen motor symptoms.
Promethazine (Phenergan): An antihistamine with anti-nausea effects that can also negatively impact PD.

Antidepressants

While antidepressants are often necessary for managing the mood disorders that accompany PD, certain types can present risks due to their effect on dopamine and other neurotransmitter systems.

Tricyclic Antidepressants (TCAs) and Selective Serotonin Reuptake Inhibitors (SSRIs) can interact with MAO-B inhibitors, which are sometimes used in PD treatment, potentially causing a dangerous condition called serotonin syndrome.
The herbal supplement St. John's wort is also not recommended for people with PD due to potential interactions.

Cold, Flu, and Allergy Medications

Over-the-counter cold and flu remedies containing decongestants and stimulants can interfere with PD medications and worsen symptoms. This is particularly relevant for those taking MAO-B inhibitors.

Active Ingredients to Watch For: Products containing pseudoephedrine or stimulants should be avoided. A pharmacist can provide guidance on safer alternatives.

Comparison of Risky and Safer Drug Alternatives


Drug Class	Medications to Use with Caution/Avoid	Safer Alternatives (Consult Your Doctor)
Antipsychotics	Haloperidol (Haldol), Risperidone (Risperdal), Olanzapine (Zyprexa)	Pimavanserin (Nuplazid), Clozapine (Clozaril), Quetiapine (Seroquel)
Antiemetics	Metoclopramide (Reglan), Prochlorperazine (Compazine), Promethazine (Phenergan)	Domperidone (Motilium) (note: potential heart risks), Ondansetron (Zofran)
Antidepressants	Most SSRIs, TCAs (especially with MAO-B inhibitors)	Paroxetine (Paxil), Venlafaxine (Effexor XR) (often safer, but require close monitoring)
Blood Pressure Drugs	Methyldopa (Aldomet), Reserpine (Serpalan)	ACE inhibitors, ARBs, Beta-blockers (use with caution, as they may have some interactions)
Pain Relievers	Meperidine (Demerol) (with MAO-B inhibitors)	Acetaminophen (Tylenol), ibuprofen (Advil)

Medication Management Best Practices

Effective medication management is critical for people with Parkinson's. This involves a collaborative effort between the patient, family members, and the entire healthcare team.

Maintain a Comprehensive List: Always keep an up-to-date list of all medications, including prescription drugs, over-the-counter products, and supplements. This is especially important during hospital admissions.
Consult All New Medications: Before starting any new medication, even over-the-counter, always check with a specialist, pharmacist, or Parkinson's disease nurse specialist.
Do Not Stop Abruptly: Never stop or change the dose of any Parkinson's medication without a doctor's guidance, as this can severely worsen symptoms.
Time Medications Appropriately: For certain drugs like levodopa and iron supplements, staggering the intake by at least two hours is necessary to ensure proper absorption and effectiveness.
Educate Healthcare Providers: Inform all healthcare providers, including dentists and specialists for other conditions, about the PD diagnosis to prevent the prescription of contraindicated medications.

Conclusion

It is vital for people with Parkinson's to be vigilant about the medications they take, as many common drugs can interfere with PD treatment and worsen symptoms. By understanding which medications are bad for Parkinson's, such as dopamine-blocking antipsychotics and antiemetics, patients can actively participate in their care. Keeping a detailed medication list, consulting healthcare professionals before starting new drugs, and never stopping prescribed PD medications suddenly are essential practices for ensuring safety and maintaining quality of life. With careful management and open communication with the healthcare team, the risks associated with contraindicated medications can be minimized.

This article is for informational purposes only and does not constitute medical advice. For specific concerns about your medication, consult your doctor or pharmacist.

Frequently Asked Questions

Most antipsychotic medications work by blocking dopamine receptors in the brain. Since Parkinson's is characterized by a lack of dopamine, blocking these receptors can counteract the effects of PD treatment, leading to worsened motor symptoms like tremors, slowness, and stiffness.

You should not take most over-the-counter anti-nausea medications without consulting a healthcare provider, as many contain dopamine-blocking ingredients like metoclopramide or prochlorperazine. A doctor may recommend a safer alternative such as domperidone or ondansetron.

Drug-induced parkinsonism (DIP) is a reversible condition caused by medications that block dopamine receptors, leading to symptoms that mimic Parkinson's disease. DIP can worsen existing PD and, in some cases, unmask underlying, undiagnosed Parkinson's.

Yes. While many antipsychotics are unsafe, some atypical antipsychotics are used under specialist supervision. Pimavanserin (Nuplazid) is specifically approved for PD psychosis, and clozapine (Clozaril) and quetiapine (Seroquel) are sometimes used off-label. All have specific risks and must be carefully managed by a doctor.

Yes. Many cold and flu products contain decongestants or stimulants that can interact with certain Parkinson's medications, particularly MAO-B inhibitors, and may increase side effects or decrease the effectiveness of your PD drugs. Always consult a pharmacist before taking them.

To avoid dangerous interactions, always keep a complete, current list of all your medications. Inform every healthcare provider, including specialists and dentists, about your PD diagnosis. Never start a new medication or supplement without consulting your PD specialist or pharmacist first.

Some antidepressants, like SSRIs and TCAs, can pose a risk of serotonin syndrome when combined with MAO-B inhibitors used for PD. While this is rare, it requires close medical supervision. The herbal supplement St. John's wort is also not recommended.