STUDIES ON THE INHIBITORY ACTION OF CHLORAMPHENICOL AND THIAMPHENICOL UPON ERYTHROPOIESIS

Abstract

In order to elucidate the mechanism by which both chloramphenicol (CP) and thiamphenicol (TP) induce reversible erythroid suppression, an inhibitory effect of these drugs on heme synthesis was investigated in the patients having CP and/or TP-induced acute bone marrow failure.The patients consisted of five TP cases and the case which had been given both drugs. All cases but a case of polycythemia vera had reversible erythroid suppression. The case of polycythemia vera died of cerebral thrombosis. The anemia observed at the occurrence of acute bone marrow failure were normocytic and normochromic in all cases but one of polycythemia vera, which already had low value of MCV, MCH and MCHC prior to TP administration. Among six patients one had pancytopenia, three had only anemia and two had anemia with thrombocytopenia. Normal to slightly elevated level of serum iron was observed in all cases which were measured one to two days after the occurrence of acute bone marrow failure. Morever, the appearance of ringed sideroblasts were noted in two of six cases which bone marrow examination was performed.Out of five cases examined, two showed a decrease in deltaaminolevulinic acid synthetase (δ-A-LA-s) activity while the other two did the normal values. Out of three cases two showed an increase in both free erythrocyte copro- and protoporphyrin, and the third did the normal value. Neither inhibitory effect of CP succinate nor TP on δ-ALA-s was observed in the in vitro study examined at a concentration of less than 10-3 mol of CP or TP.