Spermidine, also known as N-(3-Aminopropyl)-1,4-butanediamine, is a naturally occurring polyamine compound found in ribosomes and living tissues. It was first isolated from semen, which is reflected in its name. Structurally, spermidine is a linear molecule with three amine groups, contributing to its polycationic nature at physiological pH. It can be synthesized through the decarboxylation of S-adenosylmethionine, which is catalyzed by the enzyme spermidine synthase. Researchers have extensively studied spermidine for its potential role in promoting cellular longevity and health. It has been observed to induce autophagy, a cellular process that removes damaged organelles and proteins, thereby contributing to cellular maintenance and longevity. Studies have also suggested its involvement in reducing oxidative stress and inflammation, which are key factors in aging and age-related diseases. The mechanism of action of spermidine primarily involves the induction of autophagy through the inhibition of acetyltransferases, leading to the deacetylation of key autophagy-related proteins. This process is crucial for the maintenance of cellular homeostasis and has been linked to increased lifespan in various model organisms. Pharmacokinetic data on spermidine is limited, but it is known to have poor oral bioavailability due to its polycationic nature, which affects its absorption. Its stability and half-life in various administration routes remain largely unexplored. Current research on spermidine is focused on its potential therapeutic applications in aging and neurodegenerative diseases. It is not approved as a medicinal product by major regulatory agencies, and its use is primarily confined to research settings. Regulatory standing varies by country, and it is not classified as a controlled substance.