Monitoring patients on long-term drug therapy for genotoxic effects

The problems associated with the design and conduct of experiments involving surveys of human population sister chromatid exchange (SCE) frequencies are discussed. It is suggested that the problems of variation between culture occasions may be overcome by the rigid control of experimental conditions and the inclusion of the same negative controls (herein called "base controls") on all culture occasions. In addition, all experimental subjects are cultured, as far as possible, at the same time as controls drawn from the same population and matched for age (+/- 5 yr) and sex. Many factors in such surveys remain uncontrolled but the collection of data on potential environmental mutagen exposure in all subjects is suggested as a mechanism to measure and evaluate such factors. Data are reported on SCE frequencies in lymphocytes from patients receiving 4 separate drugs for chronic conditions. Using a square root transformation of SCE frequencies and the analysis of variance, there is clear evidence for a rise in SCE frequency in patients receiving sulphasalazine (SASP) and azathioprine (Aza). On the other hand, patients receiving atenolol or chlorpropamide show no evidence of a rise in SCE frequency.