Alfacalcidol

Alfacalcidol is a prodrug that is rapidly metabolized in the liver to the active form, calcitriol. As it is already 1α-hydroxylated, it does not require activation in the kidney as cholecalciferol does. After calcitriol binds to its intracellular receptor (vitamin D receptor, VDR), the synthesis of a calcium ion-binding protein increases. The compound enhances intestinal absorption of calcium and phosphate, regulates bone mineralization, and promotes calcium reabsorption in the renal tubules. == Synthesis ==

The multi-step synthesis of alfacalcidol is illustrated in the following reaction sequence: == Properties ==

Alfacalcidol is practically insoluble in water, slightly soluble in 96% ethanol, and soluble in fatty oils. It is sensitive to air, heat, and light. In solution, a reversible isomerization to pre-alfacalcidol occurs, depending on temperature and duration. Both compounds are biologically active. ==History==

Alfacalcidol was patented in 1971 and approved for medical use in 1978. ==Trade names==

Pharmaceutical trade names include AlphaD and One-Alpha. ==Other animals==

Used as a poultry feed additive, it prevents tibial dyschondroplasia and increases phytate bioavailability. == References ==