Influence of amiodarone on urinary excretion of 6 beta-hydroxycortisol in humans

The present study was undertaken to evaluate the use of cortisol 6 beta -hy droxylation in defining the effect of amiodarone on cytochrome CYP3A activi ty. To accomplish this goal, the in vivo activity of CYP3A was estimated by measuring the 24-hour urinary excretion of 6 beta -hydroxycortisol (6 beta -OHC) and by calculating 24-hour ratio of 6 beta -hydroxycortisol to urina ry free cortisol (6 beta -OHC/UFC ratio). Nine cardiac patients scheduled f or amiodarone treatment were recruited to participate in this study. Urine was collected over a 24-hour period from each subject before the first amio darone administration and during the third day of oral administration of am iodarone (200 mg four times daily as a loading dose). Three days of amiodar one treatment caused a significant decrease (p<0.05) in both the 6<beta>-OH C/UFC ratio and the 24-hour urinary excretion of 6 beta -OHC. These results suggest that amiodarone is an inhibitor of CYP3A activity.