Long-Acting Injectables: Current Perspectives and Future Promise

The parenteral route of administration is preferred over the oral route for treatment of many chronic and life-threatening diseases due to better patient compliance. Long-acting injectables/depot delivery systems are formulations intended for prolonged/sustained drug release over a long period of time ranging from a few days to months. Depot delivery systems enhance product quality by decreasing dosing frequency, simplifying the drug regimen. Parenteral depots reduce the relapse rate of disease and the maintenance phase of therapy, hence improving efficacy and treatment adherence. However, despite being extensively explored in the last seventy years, only a few depot products have been marketed or have reached commercial viability. The introduction of long-acting injectables of any drug took 9 to 10 years after approval of its oral formulation. Mainly the market has been conquered by long-acting injectables for antipsychotic, substance abuse, and hormonal therapy drugs. This article focuses on the preparation of long-acting injectables with special emphasis on challenges associated with formulation. The evolution and current global market trend of various depot formulations are also discussed. Insight is provided into the promising future of long-acting injectables of protein-based drugs as well as multidrug therapy, along with potential uses in the treatment of chronic diseases like HIV, Parkinson's, and Alzheimer's.