Parkinson’s Disease

Parkinsonism is a syndrome with symptoms that are similar to Parkinson’s disease. These symptoms can include tremor, bradykinesia or slowing of motor skills, rigidity, and postural instability, resulting in poor balance. Parkinson’s disease can be the cause of Parkinsonism, but it is not the only cause. Other causes include diseases of metabolism, other neurological conditions, and toxins. Some drug side effects include the symptoms of Parkinsonism. One main type of these medications are neuroleptic antipsychotics. These drugs work by blocking dopamine receptors or depleting stored dopamine. Dopamine is essential for motor coordination, which is why the disruption of normal dopamine activity can cause movement disorders like Parkinsonism. Drug-induced Parkinsonism (DIP) is the most common movement disorder from dopamine affecting drugs. This syndrome greatly impacts the lives of patients. It is important to understand the factors that go into deciding the right balance of benefits versus risks and factor that determine adequate dosage.

This review focuses on Parkinsonism resulting from medication use, or DIP. The first study shows that gastrointestinal prokinetics, calcium channel blockers, atypical antipsychotics, and antiepileptic drugs can cause Parkinsonism. This study found that a dopamine blockage can cause changes in the basal ganglia motor circuit resulting in the syndrome. Its results showed that the syndrome does not cease with discontinued use of the drug. Another study examined Olanzapine-induced Parkinsonism. This is an atypical antipsychotic. A third study looked at neuroleptic-induced Parkinsonism and added an interesting association. People with olfactory dysfunction were more likely to develop Parkinsonism as a side effect. The previous three studies assessed occurrences in the elderly population, but a fourth study looked at two cases of drug induced Juvenile Parkinsonism which is when the onset occurs before 21 years of age.

Shin and Chung (2012) discussed how DIP is often misdiagnosed with Parkinson’s disease. This misdiagnosis is common because the signs and symptoms are very similar and almost indistinguishable. The biggest clue that someone is presenting with DIP is often found by getting a thorough medical history. Typical antipsychotics (neuroleptics), atypical antipsychotics, gastrointestinal (GI) motility drugs, calcium channel blockers, and antiepileptic drugs have been shown to cause DIP in some patients; neuroleptics being the most common. Antipsychotic drugs work by blocking the D2 receptors, which are coupled to a G protein. This inhibits the activity of enzyme adenylyl cyclase and directly inhibits cAMP formation. In the limbic system, dopamine transmission is reduced. In the striatum, GABA and encephalin-containing striatal neurons are activated. Over 80% of D2 receptors were blocked in patients with DIP (Shin and Chung, 2012). After this blockade, changes in the basal ganglia motor circuit