Chan Su

Traditional Chinese medicines are readily available without prescription in local Chinese herbal stores. One such Chinese medicine is Chan Su, which is prepared from the dried white secretion of the auricular glands and the skin glands of Chinese toads (Bufo melanostictus Schneider or Bufo bufo gargarzinas Gantor). Chan Su is also a major component of traditional Chinese medicines Liu-Shen-Wan and Kyushin (79, 80). These medicines are used for the treatment of such disorders as tonsillitis, sore throat, and palpitation. Traditional use of Chan Su given in small doses also includes stimulation of myocardial contraction, anti-inflammatory effect, and analgesia (81). The cardiotonic effect of Chan Su is due to its major bufadienolides such as bufalin (Fig. 1), cinobufagin, and resibufogenin (82). Bufalin is known to block vasodilatation and increases vasoconstriction, vascular resistance, and blood pressure by inhibiting Na, K-ATPase (83).

Fushimi and Amino (84) reported a serum digoxin concentration of 0.51 nmol/L (0.4 ng/mL) in a healthy volunteer after ingestion of Kyushin tablets containing Chan Su as the major component. Panesar (85) reported an apparent digoxin concentration of 1124pmol/L (0.88 ng/mL) in a healthy volunteer who ingested LSW pills. The author used the FPIA and TDx analyzer for the study. Chan Su is the major component of LSW pills. An apparent digoxin concentration of 4.9 ng/mL (FPIA) was reported in one woman who died from ingestion of Chinese herbal tea containing Chan Su (86). Therefore, FPIA digoxin assay can be used to indirectly show the presence of Chan Su in serum in a suspected overdose, although a definite diagnosis is not possible without verification of the presence of bufalin in serum using a direct analytical technique such as HPLC combined with tandem mass spectrometry. In a recent article, Panesar commented that the digoxin measured by the FPIA in 2004 showed less sensitivity to the FPIA the authors used in 2003 to demonstrate apparent digoxin concentrations in volunteers after taking Chan Su-containing Chinese medicines (87).

Although the FPIA demonstrated the highest reported cross-reactivity with Chan Su, the Beckman digoxin assay (Synchron LX system) and Roche assay (Tian-Quant) are also affected by Chan Su. However, the magnitude of interference was almost 50% less compared with that of the FPIA. This may be related to the use of a more specific monoclonal antibody against digoxin in the assay design of both Tina-Quant and the Beckman assay although the FPIA utilizes a rabbit polyclonal antibody against digoxin (88).

Chan Su extracts also falsely increased serum digoxin concentration in vitro when FPIA (Digoxin II, TDx analyzer Abbott Laboratories) was used for serum digoxin measurement. In contrast, serum digoxin levels were falsely lowered (negative interference) when the MEIA (Abbott Laboratories) and AxSYM analyzer were used. However, the components of Chan Su responsible for digoxin-like immunoreactivity are significantly bound to serum proteins (>90%) and are virtually absent in the proteinfree ultrafiltrate. Therefore, measuring free digoxin concentration in the protein-free ultrafiltrate maybe used to eliminate the interference of Chan Su in serum digoxin measurements. A chemiluminescent digoxin assay marketed by the Bayer Diagnostics is also virtually free from interference of Chan Su (89).

Chinese Herbs

Chinese Herbs

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