Promethazine may be contraindicated in a Parkinson's disease patient because it depletes levels of which neurotransmitter?

Promethazine may be contraindicated in patients with Parkinson's disease because it depletes levels of dopamine. Parkinson's disease is characterized by a deficiency of dopamine in the brain, particularly in the nigrostriatal pathway, which is crucial for coordinating movement. Promethazine, as an antipsychotic and antihistamine, can act as a dopamine antagonist, interfering with the already diminished dopamine levels in these patients. This exacerbation of dopamine depletion can worsen motor symptoms associated with Parkinson’s disease, such as rigidity, bradykinesia, and tremors. Therefore, caution is warranted when considering the use of promethazine in individuals with this condition, as it could lead to significant impairment in their neurological function and overall quality of life.