The role of L-DOPA in neurological and neurodegenerative complications: a review.

L-DOPA remains a cornerstone treatment for Parkinson's disease and is increasingly recognized for its role in various neurological and neurodegenerative disorders. As a direct precursor to dopamine, L-DOPA is synthesized from L-tyrosine through the action of tyrosine hydroxylase and is subsequently converted into dopamine via aromatic L-amino acid decarboxylase. Its ability to cross the blood-brain barrier (BBB) makes it a crucial therapeutic agent for restoring dopaminergic neurotransmission, thereby influencing motor function, cognition, and neuroprotection. Beyond Parkinson's, L-DOPA's therapeutic potential extends to neurodegenerative conditions such as Alzheimer's disease, Huntington's disease, multiple sclerosis, Lewy body dementia, and amyotrophic lateral sclerosis, where dopamine modulation plays a critical role. Furthermore, L-DOPA has demonstrated efficacy in neurological disorders including epilepsy, peripheral neuropathy, cerebrovascular diseases, and traumatic brain injury, suggesting broader neurobiological applications. However, long-term use is associated with challenges such as motor fluctuations, dyskinesias, and loss of therapeutic efficacy due to progressive neurodegeneration and alterations in dopaminergic pathways. Recent advancements in drug delivery systems, combination therapies, and nanotechnology, including plant-derived carbon dots, offer promising strategies to enhance L-DOPA's effectiveness while mitigating its limitations. This comprehensive review explores L-DOPA's synthesis, pharmacokinetics, mechanism of action, and its evolving role in neurological diseases, while highlighting ongoing challenges and future directions for optimizing its clinical application.