Egualen, formulated as a sodium salt, was marketed in Japan for the
treatment of gastric ulcers and gastritis. It is a water-soluble sodium sulfonate analog of
guaiazulene, a natural azulene with anti-ulcer activity. Egualen can be prepared from an 7-
isopropyl azulen-2-yl carboxylate by successive 3-acetylation, reduction, decarboxylation
and finally, sulfonylation in l-position. The mechanism of action is not well defined; egualen is a weak inhibitor of the enzyme system H+/K+ ATPase and a weak antagonist of
prostanoid receptors; concomitantly, it was shown to possess some anti-inflammatory
properties. In animal models of gastric ulcers induced with cortisone or acetic acid, oral
treatment with egualen sodium promoted healing of ulcers and, at higher doses, mucosal
regeneration. The data available from clinical studies for egualen are limited; in one trial,
the combination of egualen sodium and cimetidine administered to patients with unhealing
gastric ulcers produced an appreciable rate of healing without any adverse events.
