Lonazolac is a nonsteroidal anti-inflammatory drug. The mononuclear cell response to a synovial stimulus can be abolished by very low concentrations of lonazolac. This blockade can be completely released by the addition of prostaglandin E2. Lonazolac appears therefore as an agent able in addition to modulate the immune response. The release of histamine from human basophils was significantly decreased after preincubation of the cells with lonazolac Ca. Preincubation of human polymorphonuclear leukocytes with lonazolac Ca led to an inhibition of leukotriene generation induced by either the Ca ionophore or opsonized zymosan. Lonazolac Ca affected different enzymes of the platelet activating factor metabolism. After pre- and post-treatment with lonazolac-Ca, the numbers of animals with lung metastases and the score of metastases significantly decreased. Lonazolac-Ca is indicated for the treatment of painful inflammatory rheumatic diseases of the joints and the spine. Acute irritation in osteoarthritis and spondylosis. Soft tissue rheumatism. Post-traumatic and postoperative pain and swelling states.