Monoethanolamine oleate Other names: cis-9-Octadecenoic acid, ethanolamine salt beta-Hydroxyethylammonium oleate

Monoethanolamine oleate is a mild sclerosing agent indicated for the treatment of patients with esophageal varices that have recently bled, to prevent rebleeding.

When injected intravenously, monoethanolamine oleate acts primarily by irritation of the intimal endothelium of the vein and produces a sterile dose-related inflammatory response. This results in fibrosis and possible occlusion of the vein. Monoethanolamine oleate also rapidly diffuses through the venous wall and produces a dose-related extravascular inflammatory reaction.

The oleic acid component of monoethanolamine oleate is responsible for the inflammatory response, and may also activate coagulation in vivo by release of tissue factor and activation of Hageman factor. The ethanolamine component, however, may inhibit fibrin clot formation by chelating calcium, so that a procoagulant action of monoethanolamine oleate has not been demonstrated.

After injection, monoethanolamine oleate disappears from the injection site within five minutes via the portal vein. When volumes larger than 20 mL are injected, some monoethanolamine oleate also flows into the azygos vein through the periesophageal vein. In human autopsy studies it was found that within four days after injection there is neutrophil infiltration of the esophageal wall and hemorrhage within six days. Granulation tissue is first seen at ten days, red thrombi obliterating the varices by twenty days, and sclerosis of the varices by two and a half months. The time course of these findings suggests that sclerosis of esophageal varices will be a delayed rather than an immediate effect of the drug.

The minimum lethal dose of monoethanolamine oleate administered intravenously to rabbits is 130 mg/kg. In dogs, monoethanolamine oleate injected into the right atrium at a dose of 1 mL/kg over one minute has been shown to increase extravascular lung water. The maximum recommended human dose is 20 mL, or 0.4 mL/kg for a 50-kg person. The concentration of monoethanolamine oleate reaching the lung in human treatment will be less than in the dog studies, but pleural effusions, pulmonary edema, pulmonary infiltration and pneumonitis have been reported in clinical trials, and minimizing the total per-session dose, especially in patients with concomitant cardiopulmonary disease, is recommended.