Adverse effects of medications used to treat motor symptoms of Parkinson′s disease: A narrative review

BACKGROUND: In the 1960s, levodopa was first administered to treat the symptoms of Parkinson's disease (PD), and it has since become the "gold standard" in its treatment. Since then, many classes of drugs have been made available to treat PD; however, these drugs are associated with considerable adverse effects. OBJECTIVE: The objective of this review is to highlight the most important and clinically relevant side effects of the medications used to treat the motor symptoms of PD. MATERIAL AND METHODS: We used PubMed and Google scholar to search for articles from January 1975 to January 2021. RESULTS: The medications used to treat PD vary in their mechanisms of action. The major classes of drugs that are used include levodopa and dopamine agonists. Nausea, vomiting, sleepiness, and neuropsychiatric and cardiovascular problems are some of the most common adverse effects observed. In addition, class-specific adverse effects of various drugs are observed and are important. CONCLUSIONS: The drugs used to treat PD are associated with considerable adverse effects, which may be mild, severe, or even life threatening. Most adverse effects are reversible and disappear with drug withdrawal. However, discontinuation of the drugs may not always be possible. Education of the patient and caregiver and awareness among clinicians is essential for early recognition and to prevent impairment of the quality of life. In addition, the development of new drugs with a favorable side effect profile should be prioritized.