Chinese medicines that contain bufalin, such as Chan Su, Lu-Shen-Wan and Kyushin, can interfere with some immunoassay methods of
digoxin, particularly the fluores- cence polarisation immunoassay. Similarly, a study found that a fluorescent polarization immunoassay method (Abbott Laboratories) for
digoxin gave falsely high readings in the presence of danshen, whereas a microparticle
enzyme immunoassay (Abbott Laboratories) gave falsely low readings.
It has been suggested that the false readings caused by bufalin could be eliminated by monitoring the free (i.e. unbound)
digoxin concentrations or by using a chemiluminescent assay. Similarly, to reduce the interference from danshen, measure free
digoxin levels or choose assay systems that are unaffected by the presence of danshen (said to be the Roche and Beckman systems or an
enzyme linked chemiluminescent immunisorbent
digoxin assay by Bayer HealthCare).