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©2013 Baishideng Publishing Group Co.
World J Gastroenterol. May 21, 2013; 19(19): 2864-2882
Published online May 21, 2013. doi: 10.3748/wjg.v19.i19.2864
Published online May 21, 2013. doi: 10.3748/wjg.v19.i19.2864
Table 1 Essential steps of herbal hepatotoxicity assessments
Quality specifications |
Herbal product quality |
Good agricultural practices |
Good manufacturing practices |
Definition of plant family, subfamily, species, subspecies, and variety |
Definition of plant part |
Definition of solvents and solubilizers |
Lack of impurities, adulterants, and misidentifications |
Minimum of batch and product variability |
Lack of variety to variety variability |
Clinical assessment quality |
Brand name with details of ingredients, plant parts, batch number, and expiration date |
Identification as herbal drug or herbal supplement |
Herb as an ingredient of a polyherbal product or an undetermined herbal product |
Manufacturer with address |
Indication of herbal use with dates of symptoms leading to herbal treatment |
Daily dose with details of the application form |
Exact date of herb start and herb end |
Accurate dates of emerging new symptoms after herb start in chronological order |
Accurate date of initially increased liver values |
Timeframes of challenge, latency period, and dechallenge |
Verification or exclusion of a temporal association |
Provided temporal association is verified, evaluation of a causal relationship |
Gender, age, body weight, height, body mass index |
Ethnicity, profession |
Past medical history regarding general diseases and specifically liver diseases |
ALT value initially including normal range |
ALT values during dechallenge at least on days 8 and 30, as well as later on |
ALT values during dechallenge to exclude a second peak |
ALT normalization with exact date and actual value |
ALP value initially including normal range |
ALP values during dechallenge up to 180 d, as well as later on |
ALP values during dechallenge to exclude a second peak |
ALP normalization with exact date and actual value |
AST value initially including normal range |
Laboratory criteria for definition of hepatotoxicity and its pattern |
Definition of risk factors such as age and alcohol |
Alcohol and drug use |
Statement regarding actual treatment including steroids or ursodesoxycholic acid |
Assessment of preexisting and coexisting liver unrelated diseases |
Assessment of preexisting and coexisting liver diseases |
Consideration of the several hundreds of other possible liver diseases |
Providing details to exclude alternative diagnoses |
Assessment and exclusion of hepatitis A virus, hepatitis B virus, hepatitis C virus, hepatitis E virus, cytomegalovirus, Epstein-Barr virus, HSV, VZV |
Liver and biliary tract imaging including color Doppler sonography of liver vessels |
Specific evaluation of alcoholic, cardiac, autoimmune, and genetic liver diseases |
Individual quantitative score of each alternative diagnosis |
Comedicated synthetic drugs, herbal drugs, herbal and other dietary supplements |
Definition of and search for accidental, unintended reexposure |
Assessing of unintended reexposure |
Search for evidence of prior known hepatotoxicity of the suspected herb |
Assessing of known hepatotoxicity caused by the herb |
Qualified data acquisition and documentation of complete data |
Transparent presentation of all data |
Causality assessment quality |
Prospective assessment by the physician suspecting herb induced liver injury |
Structured and quantitative method |
Liver specific causality assessment method validated for hepatotoxicity |
Use of the CIOMS scale |
Gathering of all data required for the CIOMS scale item by item |
Presentation of individual CIOMS items and of scores to regulatory agency |
Gathering all clinical data and presentation to regulatory agency |
Excluding all alternative causes and presentation to regulatory agency |
Regulatory case assessment by skilled hepatologist with clinical experience |
Regulatory assessment with assistance of external experts |
Transparent presentation of regulatory verified causality assessment results |
Table 2 Check list for herb induced liver injury diagnosis
Items to be assessed | Information obtained | ||
Yes | No | Partial | |
Brand name with batch number and expiration date | □ | □ | □ |
Indication of herbal use | □ | □ | □ |
Dates of symptoms leading to herbal treatment | □ | □ | □ |
Daily dose | □ | □ | □ |
Application form of herbal product | □ | □ | □ |
Exact date of herb start | □ | □ | □ |
Exact date of herb end | □ | □ | □ |
Accurate dates of emerging new symptoms after herb start in chronological order | □ | □ | □ |
Accurate date of initially increased liver values | □ | □ | □ |
Time frame of challenge | □ | □ | □ |
Time frame of latency period | □ | □ | □ |
Time frame of dechallenge | □ | □ | □ |
Verification of temporal association | □ | □ | □ |
Exclusion of temporal association | □ | □ | □ |
Gender, age, body weight, height, BMI | □ | □ | □ |
Ethnicity, profession | □ | □ | □ |
Past medical history and actual assessment regarding preexisting general diseases | □ | □ | □ |
Past medical history and actual assessment regarding preexisting liver diseases | □ | □ | □ |
Risk factors such as age and alcohol | □ | □ | □ |
Quantification of alcohol and drug use | □ | □ | □ |
Comedicated synthetic drugs, herbal drugs, herbal and other dietary supplements with all details of product, daily dose, exact dates of start and end of use, indication | □ | □ | □ |
ALT value initially including exact date and normal range | □ | □ | □ |
ALT values during dechallenge at least on days 8 and 30, and later on, with exact dates | □ | □ | □ |
ALT values during dechallenge to exclude a second peak, with exact dates | □ | □ | □ |
ALT normalization with exact date and actual value | □ | □ | □ |
ALP value initially including exact date and normal range | □ | □ | □ |
ALP values during dechallenge up to 180 d, and later on, with exact dates | □ | □ | □ |
ALP values during dechallenge to exclude a second peak, with exact dates | □ | □ | □ |
ALP normalization with exact date and actual value | □ | □ | □ |
AST value initially including normal range | □ | □ | □ |
Laboratory criteria for definition of hepatotoxicity | □ | □ | □ |
Laboratory criteria for injury pattern | □ | □ | □ |
Liver and biliary tract imaging including hepatobiliary sonography, CT, MRT, MRC | □ | □ | □ |
Color Doppler sonography of liver vessels | □ | □ | □ |
Unintended reexposure | □ | □ | □ |
Known hepatotoxicity caused by the herb | □ | □ | □ |
Consideration and exclusion of other possible causes | □ | □ | □ |
Hepatitis A | □ | □ | □ |
Anti-HAV-IgM | |||
Hepatitis B | □ | □ | □ |
HBsAg, anti-HBc-IgM, HBV-DNA | |||
Hepatitis C | □ | □ | □ |
Anti-HCV, HCV-RNA | |||
Hepatitis E | □ | □ | □ |
Anti-HEV-IgM, anti-HEV-IgG, HEV-RNA | |||
CMV | □ | □ | □ |
CMV-PCR, titer change for anti-CMV-IgM and anti-CMV-IgG | |||
EBV | □ | □ | □ |
EBV-PCR, titer change for anti-EBV-IgM and anti-EBV-IgG | |||
HSV | □ | □ | □ |
HSV-PCR, titer change for anti-HSV-IgM and anti-HSV- IgG | |||
VZV | □ | □ | □ |
VZV-PCR, titer change for anti-VZV-IgM and anti-VZV-IgG | |||
Other virus infections | □ | □ | □ |
Specific serology of Adenovirus, Coxsackie-B-virus, Echovirus, Measles virus, Rubella virus, Flavivirus, Arenavirus, Filovirus, Parvovirus, HIV, and others | |||
Other infectious diseases | □ | □ | □ |
Specific assessment of bacteria, fungi, parasites, worms, and others | |||
AIH type I | □ | □ | □ |
Gamma globulins, ANA, SMA, AAA, SLA/LP, anti-LSP, anti-ASGPR | |||
AIH type II | □ | □ | □ |
Gamma globulins, anti-LKM-1 (CYP 2D6), anti-LKM-2 (CYP 2C9), anti-LKM-3 | |||
PBC | □ | □ | □ |
AMA, anti-PDH-E2 | |||
PSC | □ | □ | □ |
p-ANCA, MRC | |||
AIC | □ | □ | □ |
ANA, SMA | |||
Overlap syndromes | □ | □ | □ |
See AIH, PBC, PSC, and AIC | |||
NASH | □ | □ | □ |
BMI, insulin resistance, hepatomegaly, echogenicity of the liver | |||
ALD | □ | □ | □ |
Patient’s history, clinical and laboratory assessment, sonography | |||
DILI | □ | □ | □ |
Patient’s history, clinical and laboratory assessment, sonography, use of the CIOMS scale | |||
Cocaine, ecstasy and other amphetamines | □ | □ | □ |
Toxin screening | |||
Rare intoxications | □ | □ | |
Toxin screening for household and occupational toxins | |||
Hereditary hemochromatosis | □ | □ | □ |
Serum ferritin, total iron-binding capacity, genotyping for C2824 and H63D mutation, hepatic iron content | |||
Wilson’s disease | □ | □ | □ |
Copper excretion (24 h urine), ceruloplasmin in serum, free copper in serum, Coombs-negative hemolytic anemia, hepatic copper content, Kayser-Fleischer-Ring, neurologic-psychiatric work-up, genotyping | |||
Porphyria | □ | □ | □ |
Porphobilinogen in urine, total porphyrines in urine | |||
α1-Antitrypsin deficiency | □ | □ | □ |
α1-Antitrypsin in serum | |||
Biliary diseases | □ | □ | □ |
Clinical and laboratory assessment, hepatobiliary sonography, endosonography, CT, MRT, MRC | |||
Pancreatic diseases | □ | □ | □ |
Clinical and laboratory assessment, sonography, CT, MRT | |||
Celiac disease | □ | □ | □ |
TTG antibodies, endomysium antibodies, duodenal biopsy | |||
Anorexia nervosa | □ | □ | □ |
Clinical context | |||
Parenteral nutrition | □ | □ | □ |
Clinical context | |||
Cardiopulmonary diseases with shock liver (cardiac hepatopathy, ischemic hepatitis) | □ | □ | □ |
Cardiopulmonary assessment of congestive heart disease, myocardial infarction, cardiomyopathy, cardiac valvular dysfunction, pulmonary embolism, pericardial diseases, arrhythmia, hemorrhagic shock, and various other conditions | |||
Addison’s disease | |||
Plasma cortisol | □ | □ | □ |
Thyroid diseases | |||
TSH basal, T4, T3 | □ | □ | □ |
Grand mal seizures | |||
Clinical context of epileptic seizure (duration > 30 min) | □ | □ | □ |
Heat stroke | |||
Shock, hyperthermia | □ | □ | □ |
Polytrauma | |||
Shock, liver injury | □ | □ | □ |
Systemic diseases | |||
Specific assessment of M. Boeck, amyloidosis, lymphoma, other malignant tumors, sepsis and others | □ | □ | □ |
Other diseases | |||
Clinical context | □ | □ | □ |
Table 3 Methods of causality assessments for suspected herbal hepatotoxicity
Methods of causality assessment | Specific criteria of various causality assessment methods | |||||
Expert based | Structured | Qualitative | Quantitative | Liver specific | Liver validated | |
Prospective evaluation | ||||||
CIOMS scale | No | Yes | No | Yes | Yes | Yes |
MV scale | No | Yes | No | Yes | Yes | Yes |
Naranjo scale | No | Yes | No | Yes | No | No |
KL method | No | Yes | Yes | No | No | No |
Ad hoc approach | No | No | No | No | No | No |
Retrospective evaluation | ||||||
DILIN method | Yes | Yes | Yes | No | Yes | No |
WHO method | Yes | Yes | No | No | No | No |
Expert opinion | Yes | No | No | No | Yes | No |
Table 5 Updated Council for International Organizations of Medical Sciences scale for the hepatocellular type of injury with items required for causality assessment in herb induced liver injury cases
Items for hepatocellular injury | Possible score | Patient’s score |
Time to onset from the beginning of the herb | ||
5-90 d (rechallenge: 1-15 d) | +2 | |
< 5 or > 90 d (rechallenge: > 15 d) | +1 | |
Alternative: Time to onset from cessation of the herb | ||
≤ 15 d (except for slowly metabolized herbal chemicals: > 15 d) | +1 | |
Course of ALT after cessation of the herb | ||
Percentage difference between ALT peak and N | ||
Decrease ≥ 50% within 8 d | +3 | |
Decrease ≥ 50% within 30 d | +2 | |
No information or continued herbal use | 0 | |
Decrease ≥ 50% after the 30th day | 0 | |
Decrease < 50% after the 30th day or recurrent increase | -2 | |
Risk factors | ||
Alcohol use (drinks/d: > 2 for women, > 3 for men) | +1 | |
No alcohol use (drinks/d: ≤ 2 for women, ≤ 3 for men) | 0 | |
Age ≥ 55 yr | +1 | |
Age < 55 yr | 0 | |
Concomitant herbs(s) and drug(s) | ||
None or no information | 0 | |
Concomitant herb or drug with incompatible time to onset | 0 | |
Concomitant herb or drug with compatible or suggestive time to onset | -1 | |
Concomitant herb or drug known as hepatotoxin and with compatible or suggestive time to onset | -2 | |
Concomitant herb or drug with evidence for its role in this case (positive rechallenge or validated test) | -3 | |
Search for non drug causes | ||
Group I (6 causes) | ||
Anti-HAV-IgM | ||
HBsAg, anti-HBc-IgM, HBV-DNA | ||
Anti-HCV, HCV-RNA | ||
Hepatobiliary sonography/colour Doppler sonography of liver vessels/endosonography/CT/MRC | ||
Alcoholism (AST/ALT ≥ 2 IU/L) | ||
Acute recent hypotension history (particularly if underlying heart disease) | ||
Group II (6 causes) | ||
Complications of underlying disease(s) | ||
Infection suggested by PCR and titre change for | ||
CMV (anti-CMV-IgM, anti-CMV-IgG) | ||
EBV (anti-EBV-IgM, anti-EBV-IgG) | ||
HEV (anti-HEV-IgM, anti-HEV-IgG) | ||
HSV (anti-HSV-IgM, anti-HSV-IgG) | ||
VZV (anti-VZV-IgM, anti-VZV-IgG) | ||
Evaluation of group I and II | ||
All causes-groups I and II- reasonably ruled out | +2 | |
The 6 causes of group I ruled out | +1 | |
5 or 4 causes of group I ruled out | 0 | |
Less than 4 causes of group I ruled out | -2 | |
Non herb cause highly probable | -3 | |
Previous information on hepatotoxicity of the herb | ||
Reaction labelled in the product characteristics | +2 | |
Reaction published but unlabelled | +1 | |
Reaction unknown | 0 | |
Response to readministration | ||
Doubling of ALT with the herb alone, provided ALT below 5N before reexposure | +3 | |
Doubling of ALT with the herb(s) and drug(s) already given at the time of first reaction | +1 | |
Increase of ALT but less than N in the same conditions as for the first administration | -2 | |
Other situations | 0 | |
Total score for patient |
Table 6 Updated Council for International Organizations of Medical Sciences scale for the cholestatic (± hepatocellular) type of injury with items required for causality assessment in herb induced liver injury cases
Items for cholestatic (± hepatocellular) injury | Possible score | Patient’s score |
Time to onset from the beginning of the herb | ||
5-90 d (rechallenge: 1-90 d) | +2 | |
< 5 or > 90 d (rechallenge: > 90 d) | +1 | |
Alternative: Time to onset from cessation of the herb | ||
≤ 30 d (except for slowly metabolized herbal chemicals: > 30 d) | +1 | |
Course of ALP after cessation of the herb | ||
Percentage difference between ALP peak and N | ||
Decrease ≥ 50% within 180 d | +2 | |
Decrease < 50% within 180 d | +1 | |
No information, persistence, increase, or continued herbal use | 0 | |
Risk factors | ||
Alcohol use (drinks/d: > 2 for women, > 3 for men) and pregnancy | +1 | |
No alcohol use (drinks/d: ≤ 2 for women, ≤ 3 for men) | 0 | |
Age ≥ 55 yr | +1 | |
Age < 55 yr | 0 | |
Concomitant herbs(s) and drug(s) | ||
None or no information | 0 | |
Concomitant herb or drug with incompatible time to onset | 0 | |
Concomitant herb or drug with compatible or suggestive time to onset | -1 | |
Concomitant herb or drug known as hepatotoxin and with compatible or suggestive time to onset | -2 | |
Concomitant herb or drug with evidence for its role in this case (positive rechallenge or validated test) | -3 | |
Search for non drug causes | ||
Group I (6 causes) | ||
Anti-HAV-IgM | ||
HBsAg, anti-HBc-IgM, HBV-DNA | ||
Anti-HCV, HCV-RNA | ||
Hepatobiliary sonography/colour Doppler sonography of liver vessels/endosonography/CT/MRC | ||
Alcoholism (AST/ALT ≥ 2 IU/L) | ||
Acute recent hypotension history (particularly if underlying heart disease) | ||
Group II (6 causes) | ||
Complications of underlying disease(s) | ||
Infection suggested by PCR and titre change for | ||
CMV (anti-CMV-IgM, anti-CMV-IgG) | ||
EBV (anti-EBV-IgM, anti-EBV-IgG) | ||
HEV (anti-HEV-IgM, anti-HEV-IgG) | ||
HSV (anti-HSV-IgM, anti-HSV-IgG) | ||
VZV (anti-VZV-IgM, anti-VZV-IgG) | ||
Evaluation of group I and II | ||
All causes-groups I and II- reasonably ruled out | +2 | |
The 6 causes of group I ruled out | +1 | |
5 or 4 causes of group I ruled out | 0 | |
Less than 4 causes of group I ruled out | -2 | |
Non herb cause highly probable | -3 | |
Previous information on hepatotoxicity of the herb | ||
Reaction labelled in the product characteristics | +2 | |
Reaction published but unlabelled | +1 | |
Reaction unknown | 0 | |
Response to readministration | ||
Doubling of ALP with the herb alone, provided ALP below 5N before reexposure | +3 | |
Doubling of ALP with the herb(s) and drug(s) already given at the time of first reaction | +1 | |
Increase of ALP but less than N in the same conditions as for the first administration | -2 | |
Other situations | 0 | |
Total score for patient |
Table 4 Details of the various causality assessment methods for herb induced liver injury
Assessed items with specific scores | CIOMS | MV | Naranjo | KL | Ad hoc | DILIN | WHO | Expert opinion |
Time frame of latency period (score) | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Time frame of challenge (score) | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Time frame of dechallenge (score) | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Recurrent ALT or ALP increase (score) | + | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Definition of risk factors (score) | + | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Verified alternative diagnoses (score) | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Assessed HAV, HBV, HCV (score) | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Assessed CMV, EBV, HSV, VZV (score) | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Liver and biliary tract imaging (score) | + | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Liver vessel Doppler sonography (score) | + | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Assessed preexisting diseases (score) | + | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Evaluated cardiac hepatopathy (score) | + | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Excluded alternative diagnoses (score) | + | + | + | 0 | 0 | 0 | 0 | 0 |
Comedication (score) | + | 0 | + | 0 | 0 | 0 | 0 | 0 |
Prior known herbal hepatotoxicity (score) | + | + | + | 0 | 0 | 0 | 0 | 0 |
Searched unintended reexposure (score) | + | + | + | 0 | 0 | 0 | 0 | 0 |
Defined unintended reexposure (score) | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Unintended reexposure (score) | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Laboratory hepatotoxicity criteria | + | + | 0 | 0 | 0 | + | 0 | + |
Laboratory hepatotoxicity pattern | + | + | 0 | 0 | 0 | + | 0 | + |
Liver specific method | + | + | 0 | 0 | 0 | + | 0 | + |
Structured, liver related method | + | + | 0 | 0 | 0 | + | 0 | 0 |
Quantitative, liver related method | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Validated method for hepatotoxicity | + | + | 0 | 0 | 0 | 0 | 0 | 0 |
Table 7 Council for International Organizations of Medical Sciences scale as an example with items required for causality assessment in a patient with herb induced liver injury by four Indian Ayurvedic herbs
Items for hepatocellular injury | Possible score | Psoralea corylifolia | Acacia catechu | Eclipta alba | Vetivexia zizaniodis |
Time to onset from the beginning of the herb | |||||
5-90 d (rechallenge: 1-15 d) | +2 | ||||
< 5 d or > 90 d (rechallenge: > 15 d) | +1 | +1 | +1 | +1 | +1 |
Alternative: Time to onset from cessation of the herb | |||||
≤ 15 d (except for slowly metabolized herbal chemicals: > 15 d) | +1 | ||||
Course of ALT after cessation of the herb | |||||
Percentage difference between ALT peak and N | |||||
Decrease ≥ 50% within 8 d | +3 | +3 | +3 | +3 | +3 |
Decrease ≥ 50% within 30 d | +2 | ||||
No information or continued herbal use | 0 | ||||
Decrease ≥ 50% after the 30th day | 0 | ||||
Decrease < 50% after the 30th day or recurrent increase | -2 | ||||
Risk factors | |||||
Alcohol use (drinks/d: > 2 for women, > 3 for men) | +1 | ||||
No alcohol use (drinks/d: ≤ 2 for women, ≤ 3 for men) | 0 | 0 | 0 | 0 | 0 |
Age ≥ 55 yr | +1 | +1 | +1 | +1 | +1 |
Age < 55 yr | 0 | ||||
Concomitant herbs(s) and drug(s) | |||||
None or no information | 0 | ||||
Concomitant herb or drug with incompatible time to onset | 0 | ||||
Concomitant herb or drug with compatible or suggestive time to onset | -1 | -1 | |||
Concomitant herb or drug known as hepatotoxin and with compatible or suggestive time to onset | -2 | -2 | -2 | -2 | |
Concomitant herb or drug with evidence for its role in this case (positive rechallenge or validated test) | -3 | ||||
Search for non herb causes | |||||
Group I (6 causes) | |||||
Anti-HAV-IgM | - | - | - | - | |
HBsAg, anti-HBc-IgM, HBV-DNA | - | - | - | - | |
Anti-HCV, HCV-RNA | - | - | - | - | |
Hepatobiliary sonography/colour Doppler sonography of liver vessels/endosonography/CT/MRC | - | - | - | - | |
Alcoholism (AST/ALT ≥ 2 IU/L) | - | - | - | - | |
Acute recent hypotension history (particularly if underlying heart disease) | - | - | - | - | |
Group II (6 causes) | |||||
Complications of underlying disease(s) | - | - | - | - | |
Infection suggested by PCR and titre change for | |||||
CMV (anti-CMV-IgM, anti-CMV-IgG) | - | - | - | - | |
EBV (anti-EBV-IgM, anti-EBV-IgG) | - | - | - | - | |
HEV (anti-HEV-IgM, anti-HEV-IgG) | - | - | - | - | |
HSV (anti-HSV-IgM, anti-HSV-IgG) | - | - | - | - | |
VZV (anti-VZV-IgM, anti-VZV-IgG) | - | - | - | - | |
Evaluation of group I and II | |||||
All causes-groups I and II-reasonably ruled out | +2 | +2 | +2 | +2 | +2 |
The 6 causes of group I ruled out | +1 | ||||
5 or 4 causes of group I ruled out | 0 | ||||
Less than 4 causes of group I ruled out | -2 | ||||
Non herb cause highly probable | -3 | ||||
Previous information on hepatotoxicity of the herb | |||||
Reaction labelled in the product characteristics | +2 | ||||
Reaction published but unlabelled | +1 | +1 | |||
Reaction unknown | 0 | 0 | 0 | 0 | |
Response to readministration | |||||
Doubling of ALT with the herb alone, provided ALT below 5N before reexposure | +3 | ||||
Doubling of ALT with the herb(s) and drug(s) already given at the time of first reaction | +1 | ||||
Increase of ALT but less than N in the same conditions as for the first administration | -2 | ||||
Other situations | 0 | ||||
Total score for each individual herb used by the patient | +7 | +5 | +5 | +5 |
- Citation: Teschke R, Frenzel C, Schulze J, Eickhoff A. Herbal hepatotoxicity: Challenges and pitfalls of causality assessment methods. World J Gastroenterol 2013; 19(19): 2864-2882
- URL: https://www.wjgnet.com/1007-9327/full/v19/i19/2864.htm
- DOI: https://dx.doi.org/10.3748/wjg.v19.i19.2864