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After Parkinson’s disease, drug-induced parkinsonism (DIP) is the second most common cause of parkinsonism in older adults.
“Parkinsonism” refers to a group of movement-related symptoms, such as tremors and stiffness.
Drug-induced parkinsonism, a movement disorder, is sometimes mistaken for Parkinson’s disease. Parkinson’s disease, also called idiopathic Parkinson’s disease, has no single known cause, while DIP is caused by certain drugs that interfere with the activity of dopamine, a chemical in the brain.
This article will explain what drug-induced parkinsonism is, what commonly causes it, and how it’s treated.
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Drug-induced parkinsonism is a side effect most often caused by neuroleptics (antipsychotics) and antiemetic (anti-nausea) medications. These medications can block dopamine receptors in the brain, causing tremor, stiffness, and bradykinesia (slowed movement) that can look very similar to Parkinson’s disease.
Older age is also a risk factor for DIP. Age-related changes in the brain may make some older adults more sensitive to medications that interfere with dopamine activity.
Because dopamine is a key brain chemical in movement, medications that interfere with dopamine activity can cause motor symptoms that look like Parkinson’s disease. However, in Parkinson’s, these symptoms are linked to the loss of dopamine-producing brain cells.
The signs and symptoms of drug-induced parkinsonism are similar to those of Parkinson’s disease. DIP symptoms usually develop within a few weeks but can also appear months after starting the medication. These motor symptoms include:
Some differences between the two conditions can help doctors tell them apart. DIP often affects both sides of the body, while Parkinson’s disease typically begins on one side and may worsen over time.
DIP also mainly causes movement symptoms, whereas Parkinson’s can cause other types of symptoms, such as depression and constipation.
DIP symptoms usually improve after the medication that caused them is stopped or changed. It’s important not to stop or change a medication without talking to your doctor first. Your doctor can determine whether a medication can be causing your symptoms and provide alternatives.
Doctors diagnose drug-induced parkinsonism based on a person’s medication history, when symptoms started, and results of neurological exams. It’s important that the medication history includes current and recently stopped medications, as DIP can take months to resolve after the medication is stopped.
A neurologist may also order brain imaging, such as MRI or a dopamine transporter scan (DaTscan). MRI takes detailed pictures of the brain and can help check for other causes of symptoms. A DaTscan looks at dopamine transporter availability in the brain.
During a DaTscan, a small amount of a radioactive tracer is given intravenously. The tracer travels to the brain and attaches to dopamine transporters found on nerve cells. A special camera using single-photon emission computed tomography then takes pictures that show the pattern of dopamine transporter availability in the brain.
A DaTscan can help tell Parkinson’s disease and DIP apart. Parkinson’s typically reduces dopamine transporter availability, while DIP caused only by medication typically does not.
The most common treatment for drug-induced parkinsonism is for a doctor to stop, gradually reduce, or change the medication that’s causing the parkinsonism symptoms. However, this isn’t always easy — people are prescribed their medications for important reasons.
For example, someone with schizophrenia may be prescribed a dopamine-blocking antipsychotic, such as haloperidol. In a case like that, it may not be possible to simply discontinue the medication.
Instead, a psychiatrist may switch the person to another drug that can manage their symptoms with a lower risk of causing DIP. Quetiapine and clozapine are examples of lower-risk antipsychotics.
If someone with DIP regularly takes a dopamine-blocking drug, such as one prescribed for headaches or insomnia, their doctor may recommend stopping or changing it. However, never stop taking a prescription drug or reduce the dosage without first talking to your doctor.
In some cases, the medication that caused DIP has to be continued. Doctors may then focus on treating the movement symptoms of DIP. Your doctor might recommend the following medications for off-label (not specifically approved) use:
The outlook for drug-induced parkinsonism is generally good once the medication causing it is stopped. Around two-thirds of people get better within seven weeks. However, recovery can take longer for some people, and symptoms may last up to 18 months.
Research also suggests that certain medications can unmask underlying Parkinson’s disease. This is where imaging scans may be useful. If a DaTscan shows reduced dopamine transporter availability, it may suggest that Parkinson’s, not just the medication, is contributing to the symptoms.
This information can help doctors know whether the symptoms are caused by DIP or underlying Parkinson’s disease and recommend appropriate treatment.
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Diagnosed with PD in Dec 2023 by my neurologist. Reviewing my meds she saw Chlorpromazine for migraines and told me to stop it if possible. Got instructions to wean myself off by my doctor. It took 2… read more
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