5-Ethyl-5-(1-methylbutyl)-2-thiobarbituric acid, also known as thiopental acid, is primarily used as the active moiety in the synthesis of thiopental (sodium thiopental), a short-acting barbiturate anesthetic employed for the induction and maintenance of anesthesia, particularly in surgical procedures. It serves as a key intermediate in the production of thiobarbiturate derivatives, which are central nervous system depressants historically used as sedatives, hypnotics, and anticonvulsants. The thiobarbiturate structure enhances lipid solubility and metabolic stability compared to oxo-barbiturates, allowing rapid onset and shorter duration of action. Due to its role in controlled substances, it is restricted to research, pharmaceutical synthesis, and specialized medical applications under strict regulatory oversight.