Misoprostol is an antineoplastic drug used to treat skin growths caused by sun exposure. Masoprocol is a novel antineoplastic agent was used for the treatment of actinic keratoses (precancerous skin growths that can become malignant if left untreated). Masoprocol was withdrawn from the U.S. market in June 1996. It is not known exactly how Masoprocol works. Studies have shown that masoprocol is a potent 5-lipoxygenase inhibitor and has antiproliferative activity against keratinocytes in tissue culture, but the relationship between this activity and its effectiveness in actinic keratoses is unknown. Masoprocol also inhibits prostaglandins but the significance of this action is not yet known. Symptoms of overdose or allergic reaction include bluish coloration of skin, dizziness, severe, or feeling faint, wheezing or trouble in breathing.