To provide potassium salts of substituted cycloalkene derivatives, which suppress the production of an inflammatory mediator caused by intracellular signal transduction or cell activation induced by endotoxin, and crystals thereof. The present invention provides potassium (2-chloro-4-fluorophenyl){[(2R,3R,8R)-7-(ethoxycarbonyl)-2,3-bis(hydroxymethyl)-1,4-dioxaspiro[4.5]deca-6-en-8-yl]sulfonyl}azanide and potassium (2-bromo-4-fluorophenyl){[(2R,3R,8R)-7-(ethoxycarbonyl)-2,3-bis(hydroxymethyl)-1,4-dioxaspiro[4.5]deca-6-en-8-yl]sulfonyl}azanide, each of which suppresses the production of an inflammatory mediator caused by intracellular signal transduction or cell activation induced by endotoxin, crystals thereof, and a pharmaceutical containing any of the same, and a prophylactic and/or therapeutic agent for sepsis containing any of the same.
