Crossing the Subtle Barrier: An Ayurvedic Perspective on Brain Transport Mechanisms

The blood–brain barrier (BBB) restricts the entry of large and hydrophilic molecules, thereby limiting effective drug delivery to the brain. Contemporary approaches to overcome this challenge include selective transport strategies, nanoparticle-based systems, and non-invasive routes such as intranasal administration. Classical Ayurveda presents conceptual parallels through the doctrines of Doṣhas, Srotas, and Nyāyas, including Kedāra-Kuḷya Nyāya and Khale-Kapota Nyāya, which describe the distribution of nutrients and tissue-specific targeting. Lipid-based formulations such as Ghṛta and Medhya Rasāyanas correspond with the lipid-rich architecture of neural tissue, suggesting a rational basis for their neurological applications. However, the precise mechanisms by which these formulations influence BBB dynamics remain inadequately explored. This review integrates classical Ayurvedic principles with contemporary insights into BBB biology to elucidate potential correlations in structure and transport mechanisms. Primary sources included the Bṛhattrayī, authoritative commentaries, and the Ayurvedic Pharmacopoeia of India, while relevant peer-reviewed literature from PubMed, Scopus, and Google Scholar was analyzed to bridge traditional constructs with modern evidence. Conceptual parallels were identified between Srotas and microvascular networks, Paramāṇu and molecular dimensions, and Nyāyas and passive or active transport phenomena. Descriptions of Sūkṣma and Sthūla Srotas reflect size-dependent permeability and endothelial regulation. Functional analogies were observed between Vyāna Vāyu and neural perfusion, Tarpaka Kapha and cerebral nourishment, and Prāṇa Vāyu and respiratory exchange. Additionally, Nasya demonstrates correspondence with intranasal delivery pathways that partially bypass the BBB. These convergences suggest that Ayurvedic microstructural theory may provide a complementary interpretative framework for understanding BBB physiology and targeted brain drug delivery.