Introduction

An increasing number of herbal remedies are now being reported as hepatotoxic, with such reports on Chinese herbal products (CHPs) recently including a variety of types, such as Radix scutellariae, Radix bupleuri,[1] Herba ephedrae,[2] Radix polygoni multiflori,[3] Atractylodis macrocephalae rhizoma, Radix glycyrrhizae,[4] Radix paeoniae, Cortex moutan, and Cortex dictamni.[5], [6] However, regular users seem still to regard these remedies as ‘natural’ and nontoxic.[7] CHPs are also prescribed for chronic hepatitis[8] in Taiwan, especially in patients with hepatitis B virus (HBV) infection.[9]

CHPs containing Radix bupleuri, such as Da-Chai-Hu-Tang (Dai-saiko-to, TJ-8) and Xiao-Chai-Hu-Tang (syo-saiko-to, TJ-9) have been reported to induce hepatotoxicity.[1], [10], [11], [12] Among them, Xiao-Chai-Hu-Tang is often prescribed to treat HBV infection and the usual posology for Radix bupleuri is doses of 3–9 g/day. [8], [13], [14] However, another study undertaken in Hong Kong found that 32% of the patients with HBV infection had used CHPs, and 9% of them experienced moderate to severe side effects.[15]

Drug- or herb-induced liver injury is usually difficult to detect.[16], [17] A post-market pharmacoepidemiologic survey in a large automated database provides a method to detect the risk associated with herbal medications. The National Health Insurance (NHI) program in Taiwan is a universal system of compulsory health insurance that has been providing coverage for 96.2% of the population of Taiwan since the end of 2000. The Taiwanese government reimburses not only general healthcare expenditures but also the costs of prescriptions for CHPs (amounting to 780 different kinds of single herbs and mixed formulae in concentrated extract form). [18] This computerised database of CHPs provides us with an invaluable opportunity to undertake a population-based study.

This study was conducted to determine the association between the use of CHPs containing Radix bupleuri and the risk of hospitalisation related to liver injury among HBV-infected patients in Taiwan.

Methods

Results

After conforming to the inclusion and exclusion criteria from the population with 639,779 patients with HBV infection, the sample was comprised of 1,080 cases with at least one 30-day referent exposure window during the study period. Among them, 13.4% were 60 year of age or older, with a mean age of 40.2±14.6 years. Table 1 shows that case subjects had larger Charlson co-morbidity index scores and more pre-admission use of hepatotoxic drugs and CHPs per person than control subjects had.

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Table 1. Characteristics, co-morbidities, prescriptions and time-dependent hepatotoxic drugs for study subjects with viral hepatitis B infection, 1997–2004.

https://doi.org/10.1371/journal.pone.0016064.t001

In the case-control design, the adjusted OR during the 30-day window was 1.90 (95% Confidence Interval (CI): 1.30 to 2.77) between all products with Radix bupleuri and admissions with liver injury. The risks from Xiao-Chai-Hu-Tang and Long-Dan-Xie-Gan-Tang were significantly high, and the tests for trends in the dose-response reaction were significant. The additional risk incurred by adding each 19 gm dose of Radix bupleuri was 2.19 (CI: 1.66 to 2.89). The results using the case-crossover design remained similar.

Discussion

Although our study found that the prescription of two CHPs containing Radix bupleuri, Xiao-Chai-Hu-Tang and Long-Dan-Xie-Gan-Tang, increased the risk of hospitalisation for liver injury among HBV-infected subjects, it does not necessarily follow that the association might be causal. We have following arguments to suspect that the hypothesis is plausible.

The risk trends were consistent in both designs—case-control and case crossover, and there seems a dose-response relationship, as summarized in the Table 2. To prevent potential confounding by misdiagnosis, we deliberately included only patients who were hospitalised and excluded other possible causes of hepatobiliary diseases, including all other hepatitis-related infections, alcohol-related liver disorders, cholelithiasis and de-compensated hepatic conditions, as these conditions might make patients more likely to suffer liver injury from exposure to potentially hepatotoxic drugs. Our estimates were more conservative as we did not include the above cases. Because we did not have any direct access to the original clinical data, our study was necessarily limited to the more severe cases resulting in hospitalisations, which may increase the validity of the diagnosis but undoubtedly resulted in an underestimation of hepatotoxicity with only mild manifestations.

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Table 2. Number of exposed subjects with viral hepatitis B in the 30-day windows and adjusted odds ratios between hospitalisations with liver injury and Chinese herbal products with Radix bupleuri by case-control and case-crossover designs, 1997–2004.

https://doi.org/10.1371/journal.pone.0016064.t002

Another potential explanation is the confounding by indication, as the two major CHPs were frequently prescribed by Chinese medicine doctors to treat hepatitis. However, the most frequently prescribed CHP containing Radix bupleuri for subjects with HBV infection was Jia-Wei-Xia-Yao-San and the adjusted OR was 1.87 (CI: 0.69 to 5.06) by case-crossover design (Table 2). Moreover, prescriptions of all the other CHPs containing Radix bupleuri combined together did not show a significantly higher risk of liver injury, either. As these products were usually prescribed to HBV-infected patients, or, supposedly to be associated with HBV infection, the results of no existing association in other CHPs might serve as a contrast against the possibility of confounding by indication. However, since the number for each individual CHPs is small, we cannot draw a strong inference.

To test the potential dose-response relationship, we summed up the cumulative prescribed doses of Radix bupleuri for every window period of each patient, and then stratified the groups into 0, below and above the median dose of 19 gm. We detected a statistically significant linear trend between the increased dose and hospitalization related to liver injury (Table 2). We conducted further sensitivity analyses by stratification to clarify the misclassifications and potential confounders in the case-crossover design. The results reveal no significant changes in the ORs of the subgroups stratified by different prescribing conditions, matched patterns and co-morbidities.[16] Although the medications being studied were co-prescribed with seven potentially hepatotoxic drugs, the results reveal no significant contributions of drug-drug interactions. (Appendix S1) Since there is no other alternative explanation for the reasons of hospitalisation, we tentatively conclude that the association between liver injury and CHPs containing Radix bupleuri in HBV-infected patients exists and deserves our attention.

In Japan, Xiao-Chai-Hu-Tang and other CHPs containing Radix bupleuri produced no significant effect of acute and chronic toxicity on rats.[25] However, these animals were not suffering from HBV infection. With a retrospective study of reviewing HBV-infected cases with liver injury, Yuen et al. found 45 cases with suspected CHP-associated liver injury. [26] A hospital-based questionnaire survey found 10 of 116 patients who had taken CHPs experienced side effects.[15] But they did not explore the detailed active ingredients in the exposed CHPs. The only one clinical trial that involved applying Xiao-Chai-Hu-Tang in 16 HBV-infected patients with cirrhosis for 60 months (or, a total of 80 person years) did not detect any side effect.[27] Our study is conducted on a nation-wide basis and followed for 7 years, of which we collected 281,982 person-years of exposure to Xiao-Chai-Hu-Tang and there were a total of 224 cases with liver injury that required hospitalisation, which reveals an annual incidence rate of 7.94×10⁻⁴ per year, while that of Long-Dan-Xie-Gan-Tang is 5.96×10⁻⁴.

Potential limitations of this study, including unmeasured confounders, use of other out-of-pocket drugs, and patient compliance should also be discussed. First, the NHI reimburses for prescribed CHPs in concentrated extract form only, whereas herbal stores can sell raw herbs for patients to self-prepare decoction, according to the Pharmaceutical Affairs Law in Taiwan. The potential impact of current practices should not be ignored. However, as self-purchased raw herbs were not regularly reimbursed, people usually take them once in a while or when the CHPs fails to improve the symptom. Thus, the cumulative dose is usually small after stratification for different window periods. Furthermore, if such habits among patients remained unchanged within a 2-year period, the case-crossover design might eliminate this potential confounding, taking the advantage of each patient serving as his/her own control. Finally, this study also presumed that all prescribed medications were actually taken by subjects as prescribed, which may overestimate the actual ingested dosage, as some degree of noncompliance is always expected.

Supporting Information