Benserazide hydrochloride is primarily used in the treatment of Parkinson's disease. It is often administered in combination with levodopa to enhance the therapeutic effects of the latter. By inhibiting the enzyme aromatic L-amino acid decarboxylase (AADC) in peripheral tissues, it prevents the premature conversion of levodopa to dopamine outside the brain. This ensures a higher concentration of levodopa reaches the central nervous system, where it is converted to dopamine, thereby alleviating the motor symptoms associated with Parkinson's disease. This combination therapy helps to reduce the dosage of levodopa required, minimizing side effects such as nausea and cardiovascular issues. Additionally, it improves the overall management of symptoms, providing better control of tremors, rigidity, and bradykinesia in patients.