[Changes in immunological parameters in vitro and in vivo due to midazolam]

We investigated in vitro the influence of midazolam concentrations ranged between 0.2 and 1.6 microgram/ml on immunological parameters by using the rosette-inhibition-test and the lymphocyte-transformation-test. Additionally, in vivo studies using the lymphocyte-transformation-test and the immunomodulatory activity of serum were performed in young volunteers during experimental determination of hypnotic threshold concentration of midazolam. In vitro, no significant evidence of immunodepression could be demonstrated in a concentration range usually achieved during anaesthesia. In vivo, midazolam concentrations between 0.4-0.8 microgram/ml more likely increased than decreased the reagibility of lymphocytes. This was determined by the lymphocyte-transformation-test, especially for T-lymphocytes stimulated by the mitogens phytohemagglutinin and concanavalin A. Thus, midazolam demonstrates no immunosuppressive effect in concentrations achieved during anaesthesia as could be observed by tests of cellular immune competence. However, one has to take into consideration that only parts of the immunesystem could be examined with these tests.