Linetastine has anti-inflammatory and anticarcinogenic effects. It is a potent inhibitor of 5-lipoxygenase. It also inhibits histamine release and epidermal cyclooxygenase activity. It also markedly inhibited TPA-stimulated leukotriene B4 formation, but inhibited formation of prostaglandin E2, a cyclooxygenase product, only slightly. This suggested that neither cyclooxygenase inhibition nor antihistaminic activity were essential to the anti-inflammatory action of linetastine. The anti-inflammatory effect of oral linetastine is probably due to 5-lipoxygenase inhibition. Oral administration of linetastine almost completely suppressed Cyp1a1 mRNA levels in mouse epidermis induced by a topical application of 3-methylcholanthrene or benzo[a]pyrene to mouse skin. Oral administration of linetastine inhibited DMBA-caused skin tumor initiation at least in part by inhibiting Cyp1a1 mRNA induction and epidermal aryl hydrocarbon hydroxylase activity. Linetastine had been in phase II clinical trial for the treatment of allergic rhinitis. However, this study was discontinued.