Inverse relationship between serum cholinesterase activity and the administration of cyclophosphamide: an Index of cyclophosphamide therapy

Abstract

To determine whether serum cholinesterase activity can be a monitoring index of cyclophosphamide therapy in patients with steroid-resistant glomerulopathy, we compared the cholinesterase activity of 37 patients who received a combined therapy that included the use of cyclophosphamide, prednisolone, antiplatelet drugs, and anticoagulant drugs, with the cholinesterase activity of 25 patients who received prednisolone therapy that excluded cyclophosphamide from the combined therapy. In the prednisolone and the combined groups, cholinesterase activity declined as shown in the following formula: Y = 371-26.4 x log(X): (r2 = 0.28), Y = 444-147.7 x log(X): (r2 = 0.95), respectively. (Y: cholinesterase activity, X: the day after treatment). In the combined therapy group, the prevalence of adverse reactions following treatment in the subgroup below 200 U/l of cholinesterase activity was significantly greater (P < 0.01) than that in the subgroup above 200 U/l of cholinesterase activity. However, there was no significant difference (P < 0.25) in the prevalence of adverse reactions between the subgroups with more or less than 184 U/l of cholinesterase activity following treatment. These results suggest the importance of not going below 200 U/l of cholinesterase activity after treatment when the normal cholinesterase activity range is between 300 and 760 U/l (e.g. less than 65% of the lowest value of the normal range of other hospitals) in order to eliminate the hazards of cyclophosphamide to the patients with steroid-resistant glomerulopathy.