Procyclidine hydrochloride is primarily used in the treatment of Parkinson's disease and parkinsonism caused by antipsychotic medications. It helps to alleviate symptoms such as tremors, muscle stiffness, and spasms by blocking certain neurotransmitters in the brain. Additionally, it is effective in managing extrapyramidal side effects that arise from the use of neuroleptic drugs. In some cases, it is also prescribed for the treatment of akathisia, a condition characterized by restlessness and an inability to stay still. The compound works by restoring the balance of acetylcholine and dopamine in the central nervous system, improving motor control and reducing involuntary movements.