Drug-Induced Parkinsonism - An Insight

Introduction:

Drug-induced Parkinsonism is the type of Parkinsonism caused by drugs and is the second most common cause of Parkinsonism in the older population. About 7% of secondary Parkinsonism is drug-induced Parkinsonism and caused by the consumption of a particular type of medication. Individuals with idiopathic Parkinsonism are also at risk of developing the condition. Earlier, it was thought that this condition was a complication of antipsychotics, but it was understood later as a common fallout of the use of antidepressants, calcium channel antagonists, gastrointestinal prokinetics, antiepileptic drugs, and many other compounds. Drug-induced Parkinsonism is particularly difficult for the elderly. The management depends on identifying the symptoms and risk factors and the offending agents. Prompt discontinuation of the causative agent often leads to marked improvement, though the condition might persist or remit slowly in up to 10% of patients.

What Is Parkinsonism?

Parkinsonism is a term that indicates brain conditions like slower movements, rigidity (stiffness) of muscles, and tremors. These conditions can be seen for multiple reasons, like genetic mutations, medication reactions or, prolonged use, and infections. Parkinsonism is frequently an age-related disease. It is slightly more prevalent in males as compared to females. The most usual forms of Parkinsonism are more likely to be seen after age 60. While some of its forms can be seen at a much earlier age, the average age at which juvenile Parkinsonism starts is 17.

What Is Drug-Induced Parkinsonism?

When the symptoms of Parkinsonism disease are caused due to the intake of a particular medication, it is referred to as drug-induced Parkinsonism. In a few cases when Parkinsonism results from antipsychotic (neuroleptic) medication, it is referred to as neuroleptic-induced Parkinsonism. The medications that most probably show symptoms of this type of Parkinsonism are anti-nausea, antipsychotic drugs, etc. These medications block dopamine receptors in the nerve cells, resulting in Parkinsonism due to reduced dopamine levels. The symptoms of Parkinsonism can be reduced over time if these medications are discontinued. Parkinsonism is different from Parkinson's disease. It needs to be understood more often by many experts.

What Causes Drug-Induced Parkinsonism?

Drug-induced Parkinsonism is a result of medications taken for some other cause. These medications include antipsychotic drugs, anti-nausea medication, etc. These medications block the receptors of dopamine in the nerve cells. As a result of which, dopamine levels are reduced in the brain. Dopamine is a neurotransmitter responsible for the body's proper movement. It is also a constituent of the reward system of the brain. It makes the person feel happier and more enjoyable and helps them learn and focus on activities. The medicine that binds to and blocks dopamine receptors is a dopamine antagonist. A few medications that are responsible for causing drug-induced Parkinsonism include:

• Antipsychotics: Antipsychotic medications are used to treat several disorders, including:

1. Schizophrenia: It is a condition in which a person interprets reality abnormally.

2. Bipolar disorder- It is a mental disorder in which a person experiences extreme mood swings.

3. Alzheimer's disease- It is a mental disorder in which a person has memory-related issues.

4. Tourette syndrome- It is a nervous system disease in which a person usually performs unwanted movements or produces sounds.

5. Anxiety disorders.

6. Depression.

These medications reduce or alleviate symptoms such as delusions or hallucinations. Some antipsychotics responsible for Parkinsonism are Fluphenazine, Chlorpromazine, Promazine, Pimozide, Haloperidol, Perphenazine, etc.

• Anti-Nausea Medication: Some medications used to treat motion sickness, nausea, and vertigo block dopamine receptors and lead to Parkinsonism. These are antihistamines like Hydroxyzine, promethazine, etc.

• Gastrointestinal prokinetics: Gastric motility disorders are digestive issues seen when the nerves or muscles in the gut do not function in a coordinated way. Some medications used to treat this condition can result in Parkinsonism as a side effect. They are Metoclopramide, Prochlorperazine, and levosulpiride.

• Calcium Channel Blockers: Calcium channel blockers are the drugs that are used to treat cardiovascular issues like high blood pressure and chest pain. They are also used to treat certain neurological disorders. In some cases, calcium channel blockers might cause movement disorders and Parkinsonism. Calcium channel blockers have also been seen to reduce the risk of getting first-time Parkinson's disease. An example of a calcium channel blocker is Diltiazem.

• Anticonvulsant Medication: Valproate, an antiseizure drug that is used in treating epileptic seizures and convulsions, is the one that can most probably result in causing Parkinsonism.

• Antidepressants: Serotonin Reuptake Inhibitors (SSRIs) are largely used as antidepressants and mood stabilizers. These medications are seen to cause or worsen Parkinsonism in a few cases. Serotonin-norepinephrine reuptake inhibitors (SNRIs), another type of antidepressant, might also have this effect. SNRIs are used in treating major depressive disorders, ADHD, fibromyalgia, and many other conditions.

• Exposure to Toxins: Excessive or longer exposure to environmental toxins could be another potential cause of Parkinsonism. These chemicals are believed to result in oxidative stress or mitochondrial dysfunction, which can be a causative for movement disorders. Some toxins, like certain pesticides, may also carry a risk for Parkinson's disease. A few pesticides to be avoided are paraquat, rotenone, etc.

What Are the Signs and Symptoms of Drug-Induced Parkinsonism?

The signs and symptoms of drug-induced Parkinsonism resemble the symptoms of Parkinson's disease, which is why drug-induced Parkinsonism is often mistaken as Parkinson's disease. Both of them are different from one another. The signs and symptoms of drug-induced Parkinsonism appear rapidly, unlike Parkinson's disease, which appears gradually. People with this type of Parkinsonism have symptoms equally on both sides of the body, unlike other types of Parkinsonism, where it might be present on one side. In Parkinson's disease, the effects usually are worse on one side. The signs and symptoms of drug-induced Parkinsonism are:

• Tremors also include a resting tremor.

• Muscle stiffness.

• Gait and movement become slow.

• Issues with posture and balance.

• Impaired speech.

Is Drug-Induced Parkinsonism Reversible?

Drug-induced Parkinsonism is frequently reversible. Once the medication responsible for this is discontinued, it can be reversed. Results take time but are noted gradually. It might take around 4 to 18 months before the symptoms start subsiding. In some cases, Parkinsonism may be present after the discontinuation of medicine and progress. When this situation is seen, it is probably because the person already had or was starting to have a dopamine deficiency not linked to the medication. Parkinsonism does not cause Parkinson's disease, but it might trigger this condition in a person who is about to get it.

Conclusion

Parkinsonism is a brain condition in which the movements are slowed, stiffness is present, and tremors are seen. It is different from Parkinson's disease. People with this type of Parkinsonism have symptoms equally on both sides of the body, unlike another type of Parkinsonism where it might be present on one side.