Future trends in the development of local drug delivery systems: intraspinal, intracerebral, and intraparenchymal therapies.

Due to successful use of intrathecal drug delivery in the management of refractory pain and spasticity, new agents and indications are now being investigated. Preclinical studies of neurotrophic factors, molecules necessary for neuroneal survival and development, suggest that these agents may be beneficial for patients with neurologic disorders. Because neurotrophic factors do not cross the blood-brain barrier following systemic administration, local delivery routes, including intrathecal, intracerebroventrical, and intraparenchymal routes, are being studied; research is being conducted on intrathecal delivery for amyotrophic lateral sclerosis (ALS), intracerebroventricular delivery for Parkinson's disease and Alzheimer's disease, and intrahippocampal delivery for seizure disorders. Treatment of other neurologic disorders, such as brain tumors and HIV-related viral infections, also may be optimized by methods of local drug delivery, including intratumoral and intraparenchymal administration of potentially effective agents. Intraspinal, intratumoral, and intraparenchymal routes of administration are speculated to become critical components of treatment for a variety of neurological indications.