Gastrointestinal

Drug-induced liver injury (DILI): patterns and management

Clinical Overview and When to Suspect DILI

— Intrinsic (direct, dose-dependent): predictable, short latency (hours–days). Prototype: acetaminophen.

— Idiosyncratic (host-dependent): unpredictable, latency 5 days–6 months, not strictly dose-related. Prototypes: isoniazid, amoxicillin-clavulanate, nitrofurantoin, minocycline.

— Indirect: drug alters immune system or metabolism (checkpoint inhibitors causing immune hepatitis, rituximab reactivating HBV).

— New unexplained ↑ALT, ↑AST, ↑ALP, or ↑bilirubin in a patient on any new medication, herbal, or supplement within the past 6 months.

— Jaundice, RUQ discomfort, pruritus, fatigue, nausea after starting a drug.

— Eosinophilia, rash, fever (drug hypersensitivity pattern; think DRESS).

— Always ask specifically about acetaminophen, antibiotics (Augmentin, TMP-SMX, nitrofurantoin), statins, antiepileptics, antituberculous drugs, methotrexate, amiodarone, and herbals (kava, green tea extract, Hydroxycut, ma huang, anabolic steroids).

Definition: Drug-induced liver injury (DILI) is hepatic injury caused by prescription drugs, OTC agents, herbals/supplements, or illicit substances, after exclusion of other causes. It is the leading cause of acute liver failure (ALF) in the US, with acetaminophen alone responsible for ~50% of ALF cases.

Two broad mechanisms:

When to suspect DILI:

Epidemiology: Idiosyncratic DILI ~14–19 per 100,000 person-years. Amoxicillin-clavulanate is the single most common implicated agent in US registries.

Board pearl: Any unexplained transaminitis on Step 3 deserves a focused medication and supplement history before any imaging — the answer is often "stop the drug" before "order MRCP."

Step 3 management: In the outpatient setting, a patient presenting with new LFT elevation on amoxicillin-clavulanate or a statin requires drug cessation, repeat LFTs in 1–2 weeks, and documentation of the suspected agent on the allergy/adverse reaction list to prevent inadvertent rechallenge.

Presentation Patterns and Key History

— Hepatocellular (R ≥ 5): marked ALT/AST elevation. Classic culprits: acetaminophen, isoniazid, methyldopa, statins, NSAIDs, kava, green tea extract.

— Cholestatic (R ≤ 2): predominant ALP/bilirubin rise. Culprits: amoxicillin-clavulanate, erythromycin estolate, chlorpromazine, anabolic steroids, oral contraceptives, terbinafine.

— Mixed (R 2–5): features of both. Culprits: phenytoin, sulfonamides, carbamazepine.

— <24 h: acetaminophen toxicity.

— Days–weeks: TMP-SMX, allopurinol, antiepileptics (often with rash → DRESS).

— Weeks–months: isoniazid, amoxicillin-clavulanate (often after drug stopped), nitrofurantoin, minocycline.

— Months–years: methotrexate (fibrosis), amiodarone (steatohepatitis), nitrofurantoin (autoimmune-like chronic hepatitis).

— All prescription drugs in past 6 months with start/stop dates.

— OTC analgesics — specifically quantify acetaminophen (combination cold remedies, opioid-APAP combos).

— Herbals, weight-loss/bodybuilding supplements, teas.

— Alcohol intake (synergistic with APAP).

— Occupational solvents, mushroom ingestion (Amanita).

— IV drug use, sexual history, tattoos (viral hepatitis differential).

— Prior episodes of jaundice or LFT abnormalities.

— Hypersensitivity DILI: rash, fever, eosinophilia, lymphadenopathy → think DRESS (allopurinol, lamotrigine, sulfa drugs, phenytoin).

— Autoimmune-like DILI: nitrofurantoin, minocycline, methyldopa, statins — ANA/ASMA may be positive.

— Steatohepatitis-pattern: amiodarone, methotrexate, tamoxifen, valproate.

Three biochemical patterns (R-value = [ALT/ULN] ÷ [ALP/ULN]):

Latency clues:

History essentials (write these as orders on CCS):

Symptom clusters:

Key distinction: Amoxicillin-clavulanate DILI often presents 1–4 weeks after completion of the antibiotic course with cholestatic jaundice — patients may deny "current medications." Always ask about recent antibiotics finished weeks ago.

Board pearl: Anabolic androgenic steroid use in a young male bodybuilder with bland cholestasis and profound pruritus is a recurrent Step 3 stem.

Physical Exam Findings (and Hemodynamic Assessment)

— Often well-appearing in mild DILI; nonspecific malaise and anorexia.

— Jaundice, scleral icterus, scratch marks from pruritus (especially cholestatic pattern).

— Fever and rash → hypersensitivity DILI / DRESS.

— Maculopapular or morbilliform rash on trunk with facial edema → DRESS (allopurinol, anticonvulsants, sulfa).

— Targetoid lesions / mucosal involvement → SJS/TEN (TMP-SMX, lamotrigine, allopurinol) — these may overlap with hepatitis.

— Excoriations from pruritus in cholestatic injury.

— Tender hepatomegaly suggests acute hepatocellular injury.

— Absence of stigmata of chronic liver disease (no spider angiomas, palmar erythema, caput medusae, gynecomastia) helps distinguish acute DILI from decompensated cirrhosis.

— Splenomegaly is uncommon in acute DILI — its presence should prompt evaluation for alternative or underlying chronic liver disease.

— Tachycardia and hypotension may reflect hypovolemia, SIRS from hepatic necrosis, or evolving shock.

— Hyperdynamic circulation (warm extremities, wide pulse pressure, low SVR) is characteristic of ALF.

— Watch RR and oxygenation — ARDS and pulmonary edema can complicate severe DILI.

— Grade I: mild confusion, sleep reversal.

— Grade II: lethargy, asterixis.

— Grade III: somnolence but rousable, marked confusion.

— Grade IV: coma. Grade III/IV mandates ICU and transplant center transfer.

General appearance:

Skin and mucosa:

Abdominal exam:

Hemodynamic / systemic assessment (critical in ALF):

Neurologic exam — encephalopathy grading:

CCS pearl: When you examine a jaundiced patient on CCS, always order "mental status exam" and "asterixis check" — encephalopathy in the setting of acute hepatitis defines acute liver failure and changes disposition from floor to ICU.

Board pearl: The combination of jaundice + transaminitis + INR ≥1.5 + any encephalopathy = acute liver failure. This triad is what triggers transplant evaluation, not the bilirubin alone.

Diagnostic Workup — Initial Labs

— ALT, AST, ALP, total/direct bilirubin, albumin, total protein.

— GGT to confirm hepatic origin of elevated ALP (vs. bone).

— INR/PT — the most important measure of hepatic synthetic function in acute injury. Albumin lags (3-week half-life).

— R = (ALT/ULN) ÷ (ALP/ULN). Categorizes injury pattern and narrows differential.

— CBC (eosinophilia → hypersensitivity; thrombocytopenia → portal hypertension or DRESS).

— BMP for AKI (hepatorenal, ATN from APAP).

— Glucose — hypoglycemia is an ominous sign of hepatic failure.

— Lactate, ammonia, ABG in suspected ALF.

— Lipase if epigastric pain (rule out concurrent pancreatitis).

— Viral hepatitis: HAV IgM, HBsAg, anti-HBc IgM, anti-HCV with HCV RNA, HEV IgM (especially in older adults, immunocompromised, or returning travelers).

— Acetaminophen level — always check in any acute hepatitis, even without reported ingestion (occult overdose, staggered ingestion).

— Autoimmune workup: ANA, ASMA, anti-LKM, IgG levels.

— Ceruloplasmin if <40 years old (Wilson disease — low ALP/bilirubin ratio <4 is suggestive).

— Iron studies (hemochromatosis), alpha-1 antitrypsin if indicated.

— TSH (hypothyroidism causes mild ALT/AST elevation).

— Pregnancy test in women of reproductive age (HELLP, AFLP differential).

— Rule out biliary obstruction, mass, Budd-Chiari, portal vein thrombosis.

— Usually normal in DILI; useful for ruling out cholestatic competitors.

Core liver panel:

Calculate the R-value at presentation:

Severity assessment:

Exclude alternative etiologies (mandatory before labeling DILI):

Imaging — RUQ ultrasound with Doppler:

Step 3 management: In a patient with new jaundice and transaminitis, the standard outpatient/ED workup is liver panel + INR + viral hepatitis panel + APAP level + RUQ US + autoimmune markers + ceruloplasmin (if young) before invoking DILI. DILI remains a diagnosis of exclusion.

Board pearl: A bilirubin/ALP ratio >0.5 with ALT >5× ULN in a patient on a drug ("Hy's law") predicts ~10% mortality from idiosyncratic DILI — a critical regulatory and clinical threshold.

Diagnostic Workup — Advanced or Confirmatory Studies

— Standardized scoring tool used to assess probability of DILI causality.

— Components: time to onset, course after drug withdrawal, risk factors, concomitant drugs, exclusion of other causes, prior known hepatotoxicity, response to rechallenge.

— Score categories: highly probable (>8), probable (6–8), possible (3–5), unlikely (1–2), excluded (≤0).

— Used in research/registries; clinical judgment still drives bedside management.

— Atypical presentation, persistent injury after drug withdrawal, suspicion of autoimmune hepatitis, or concern for malignancy.

— Useful when several drugs are candidates or the patient has underlying chronic liver disease.

— Common histologic patterns: zone 3 necrosis (APAP), eosinophilic infiltrate (hypersensitivity), microvesicular steatosis (valproate, tetracycline, Reye), bland cholestasis (anabolic steroids, OCPs), granulomas (allopurinol, sulfa, phenytoin), ductopenia (vanishing bile duct syndrome — amox-clav, chlorpromazine).

— Order when cholestatic pattern persists or biliary obstruction not excluded by US.

— Rules out primary sclerosing cholangitis, choledocholithiasis, malignancy.

— HLA-B*57:01 with flucloxacillin DILI.

— HLA-B*35:02 with minocycline.

— HLA-A*33:01 with terbinafine and fenofibrate.

— Not routine but appears in board vignettes linking HLA to specific drugs.

— LFTs every 24–48 h in hospitalized patients; weekly in stable outpatients.

— Trend INR — rising INR despite drug withdrawal is a red flag for evolving ALF.

RUCAM score (Roussel Uclaf Causality Assessment Method):

Liver biopsy — when indicated:

MRCP / EUS:

HLA typing (research / select cases):

Repeat / serial labs:

Key distinction: Drug rechallenge is contraindicated for confirming DILI in most cases because of risk of fatal recurrence, except in life-saving therapies (TB drugs, chemotherapy) where it is done cautiously under specialist supervision.

CCS pearl: If your CCS case shows persistent transaminitis at 2 weeks after stopping the suspected drug, advance the clock and order MRCP and hepatology consult / liver biopsy rather than repeating the same labs indefinitely.

Risk Stratification and First-Line Management Logic

— For polypharmacy, stop the most likely culprit; if uncertain or patient is severely ill, stop all non-essential medications.

— Document the suspected agent in problem list and allergy/adverse reaction section to prevent rechallenge.

— Mild: ALT/ALP elevated, bilirubin <2.5 mg/dL, INR <1.5.

— Moderate: Bilirubin ≥2.5 or INR ≥1.5 without symptoms of decompensation.

— Moderate–severe: Above + hospitalization required.

— Severe: Hepatic dysfunction (INR ≥1.5, ascites, encephalopathy) or other organ failure.

— Fatal/transplant: Death or LT due to DILI.

— ALT or AST >3× ULN and total bilirubin >2× ULN without initial cholestasis (ALP <2× ULN) and no other cause.

— Predicts ~10% mortality or transplant need from idiosyncratic DILI.

— Triggers urgent hepatology consult.

— Mild + reliable patient: outpatient with drug cessation, LFT recheck in 3–7 days.

— Moderate or Hy's-law-positive: admit for monitoring.

— Severe / ALF features (encephalopathy, INR ≥1.5, hypoglycemia): ICU and contact transplant center.

— IV fluids, glucose monitoring, electrolyte correction.

— Avoid sedatives (mask encephalopathy).

— Lactulose for hepatic encephalopathy (grade II+).

— Vitamin K for coagulopathy if cholestatic component (often ineffective in hepatocellular ALF).

— Treat coexisting infections aggressively.

Stop the offending drug — first and most important step.

Severity grading (DILIN/FDA framework):

Hy's law (key prognostic marker):

Disposition logic:

Supportive care priorities:

Step 3 management: A patient on amoxicillin-clavulanate with jaundice and bilirubin 4, ALT 800, ALP 350, INR 1.2 → meets Hy's law → admit, stop drug, hepatology consult, daily LFTs and INR, transplant center awareness even if not yet transferring.

Board pearl: "Stop the drug" beats "give a specific antidote" on Step 3 for virtually all idiosyncratic DILI — the exam tests recognition and removal, not heroic pharmacology.

Pharmacotherapy — Specific Treatments

— Replenishes glutathione, neutralizes NAPQI metabolite.

— Use Rumack-Matthew nomogram for single acute ingestion at known time (4–24 h post-ingestion).

— Treat if: level above treatment line, unknown time, staggered ingestion, ALT elevated, or any sign of hepatotoxicity.

— IV regimen: 150 mg/kg over 1 h → 50 mg/kg over 4 h → 100 mg/kg over 16 h (21-h protocol).

— Continue NAC beyond 21 h if LFTs still rising, INR >2, or encephalopathy present.

— NAC also reduces mortality in non-APAP ALF with early-stage encephalopathy (give empirically in suspected DILI ALF).

— Silibinin (IV, where available), high-dose penicillin G, NAC, aggressive fluids; activated charcoal if early.

— L-carnitine IV.

— Cholestyramine or ursodeoxycholic acid (UDCA) for pruritus and to potentially shorten cholestasis (variable evidence).

— Antihistamines (hydroxyzine) for mild pruritus.

— Rifampin or naltrexone for refractory pruritus.

— Stop offending drug immediately.

— Systemic corticosteroids (prednisone 1 mg/kg/day taper over weeks) for severe DRESS with hepatitis.

— Supportive skin care; ICU for SJS/TEN overlap.

— Grade 2: hold ICI, prednisone 0.5–1 mg/kg.

— Grade 3–4: permanent discontinuation, methylprednisolone 1–2 mg/kg, add mycophenolate if no response in 3 days. Do not use infliximab (hepatotoxic).

— Benzodiazepines and opioids (encephalopathy mask).

— Acetaminophen >2 g/day, NSAIDs.

— Other hepatotoxic drugs until recovery confirmed.

Acetaminophen toxicity — N-acetylcysteine (NAC):

Amanita phalloides mushroom toxicity:

Valproate hepatotoxicity / hyperammonemia:

Cholestatic DILI symptomatic management:

Hypersensitivity DILI / DRESS:

Immune checkpoint inhibitor hepatitis:

Drugs to AVOID in DILI:

CCS pearl: When you suspect APAP toxicity, start NAC immediately — do not wait for the level. NAC is most effective within 8–10 hours but still beneficial later, including in established hepatic failure.

Liver Transplantation and Advanced Management

— Coagulopathy (INR ≥1.5) + any degree of encephalopathy + illness <26 weeks duration in a patient without prior liver disease.

— For acetaminophen ALF:

— Arterial pH <7.30 after resuscitation, OR

— All three: INR >6.5 (PT >100s), creatinine >3.4 mg/dL, grade III–IV encephalopathy.

— Lactate >3.5 after fluid resuscitation also predicts poor outcome.

— For non-APAP ALF (idiosyncratic DILI):

— INR >6.5 alone, OR any three of:

— Age <10 or >40, jaundice >7 days before encephalopathy, INR >3.5, bilirubin >17.5 mg/dL, drug toxicity/indeterminate etiology.

— Head-of-bed at 30°, monitor ICP if grade III/IV encephalopathy.

— Mannitol or hypertonic saline for cerebral edema; hyperventilation as bridge.

— Mechanical ventilation for grade III/IV encephalopathy.

— Continuous renal replacement therapy (CRRT) for hyperammonemia or AKI — preferred over intermittent HD.

— Empiric broad-spectrum antibiotics + antifungals at low threshold (sepsis risk high).

— Glucose infusion for hypoglycemia (frequent in ALF).

— Avoid FFP unless active bleeding or planned procedure — masks trend in INR.

— Vitamin K 10 mg IV daily ×3.

— Molecular Adsorbent Recirculating System (MARS) and plasma exchange may bridge to transplant.

— Auxiliary partial orthotopic LT in selected centers.

— Spontaneous survival ~60% in APAP-ALF; ~25% in idiosyncratic DILI-ALF without LT.

— Post-LT 1-year survival ~80%.

Acute liver failure (ALF) definition:

Liver transplant evaluation triggers (King's College Criteria):

ICU management bundle:

Bridge therapies:

Outcomes:

Board pearl: King's College Criteria is the most-tested prognostic tool in hepatology on Step 3 — memorize the APAP criteria (pH <7.3 OR triad of INR>6.5, Cr>3.4, grade III–IV encephalopathy).

Step 3 management: Early transfer to a transplant center is far more important than any specific therapy — call before the patient is intubated and unstable.

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher risk for DILI from isoniazid, amoxicillin-clavulanate, nitrofurantoin, statins.

— Polypharmacy multiplies causality dilemmas — Beers Criteria flags nitrofurantoin (avoid in CrCl <30) and chronic NSAIDs in older adults.

— Slower recovery and higher mortality once DILI develops.

— Cholestatic DILI predominates with age.

— Lower threshold for hospitalization given comorbidities, frailty, dehydration risk.

— Many drugs require dose adjustment to avoid both nephrotoxicity and indirect hepatotoxicity.

— Methotrexate, allopurinol, and TMP-SMX accumulate in CKD → higher hepatotoxicity risk.

— Avoid contrast and NSAIDs during acute DILI to prevent compounding renal injury.

— Combined hepatorenal injury in APAP overdose: NAC + CRRT (clears ammonia, lactate, supports volume management).

— Pre-existing NAFLD, hepatitis B/C, alcohol-related liver disease increases vulnerability and severity.

— Methotrexate requires baseline fibrosis assessment (FibroScan/elastography or biopsy), avoidance of alcohol, and folate supplementation.

— Statins are not contraindicated in stable chronic liver disease or compensated cirrhosis — they may actually improve outcomes; check baseline LFTs, monitor periodically, hold only if ALT >3× ULN with bilirubin elevation.

— Avoid amiodarone, methotrexate, and pyrazinamide where alternatives exist.

— Isoniazid, rifampin, pyrazinamide all hepatotoxic. In cirrhosis, use modified regimens (e.g., 2 hepatotoxic drugs in Child-Pugh A; 1 in Child-Pugh B; none in Child-Pugh C — use levofloxacin, ethambutol, amikacin, cycloserine).

— Monitor LFTs every 2 weeks initially.

— Higher DILI risk with antiretrovirals (nevirapine, efavirenz), and reactivation/flare risk with HBV/HCV coinfection.

Elderly patients:

Renal impairment:

Underlying chronic liver disease:

Tuberculosis treatment in chronic liver disease:

HIV coinfection:

Key distinction: Mildly elevated ALT alone on a statin in a patient with NAFLD is not an indication to stop the statin — Step 3 distractor. Discontinue only if ALT >3× ULN with symptoms or bilirubin rise.

Step 3 management: In elderly polypharmacy with new transaminitis, deprescribe nonessential drugs first; reconcile with pharmacist; check for OTC supplements often forgotten.

Special Populations — Pregnancy, Pediatrics, and Subgroups

— Differential for elevated LFTs in pregnancy is high-yield and must be excluded before invoking DILI:

— Hyperemesis gravidarum (1st trimester, mild ALT rise).

— Intrahepatic cholestasis of pregnancy (3rd trimester, pruritus, bile acids ↑).

— HELLP / preeclampsia (HTN, hemolysis, low platelets).

— Acute fatty liver of pregnancy (3rd trimester, hypoglycemia, encephalopathy).

— Drugs commonly causing DILI in pregnancy: methyldopa, labetalol (rare), antiepileptics, nitrofurantoin.

— APAP remains first-line analgesic in pregnancy; in overdose, NAC is safe and crosses the placenta to protect the fetus.

— Avoid methotrexate, isotretinoin, statins (teratogenicity).

— Acetaminophen overdose: same NAC protocol; common in unintentional toddler ingestion and adolescent self-harm.

— Avoid aspirin in viral illness (Reye syndrome — microvesicular steatosis, encephalopathy).

— Valproate hepatotoxicity highest in children <2 years on polytherapy; check for fatty acid oxidation disorders.

— Anti-TB drugs: lower hepatotoxicity than adults but still monitored.

— Herbal supplements (especially "natural" diet/sports products in adolescents) are an underrecognized cause.

— Anabolic-androgenic steroid use → bland cholestasis, severe pruritus, normal LFTs may surprise; bilirubin 20–40 mg/dL not uncommon.

— MDMA, cocaine → acute hepatocellular necrosis.

— Body-building supplements (hydroxycut, OxyELITE Pro) and green tea extract → severe hepatotoxicity.

— INH alone or rifapentine-INH (3HP); baseline LFTs in high-risk groups (pregnancy, postpartum, alcohol use, HIV, chronic liver disease) per CDC.

— Hold INH if ALT >3× ULN with symptoms or >5× ULN asymptomatic.

Pregnancy:

Pediatrics:

Adolescents and young adults:

Tuberculosis prophylaxis (LTBI):

Board pearl: A 3rd-trimester woman with pruritus, no rash, normal LFTs except modestly elevated ALT/ALP, and elevated serum bile acids has intrahepatic cholestasis of pregnancy — treat with UDCA, deliver at 36–37 weeks. Do not mislabel as DILI.

CCS pearl: In any pediatric APAP ingestion, start NAC even before nomogram interpretation if presentation >8 h or ingestion timing uncertain.

Complications and Adverse Outcomes

— Cerebral edema and intracranial hypertension (leading cause of death in ALF).

— Hepatorenal syndrome / acute kidney injury.

— Coagulopathy with bleeding (GI, intracranial).

— Hypoglycemia (impaired gluconeogenesis).

— Sepsis and SIRS — pneumonia, bacteremia, fungal infection.

— Acid–base disturbances: metabolic acidosis with elevated lactate (poor prognosis).

— Multisystem organ failure.

— Persistent biochemical abnormality beyond 6–12 months after drug withdrawal.

— Most common with nitrofurantoin, methyldopa, minocycline (autoimmune-like), amox-clav.

— May progress to cirrhosis (rare).

— Prolonged ductopenic cholestasis.

— Implicated drugs: amoxicillin-clavulanate, chlorpromazine, flucloxacillin, carbamazepine, TMP-SMX.

— May require liver transplantation if progressive.

— Methotrexate, amiodarone, tamoxifen, valproate; long-term use → fibrosis/cirrhosis.

— Azathioprine, 6-mercaptopurine, oxaliplatin, busulfan, cyclophosphamide.

— Presents with non-cirrhotic portal hypertension or post-HSCT painful hepatomegaly + jaundice + fluid retention.

— Nitrofurantoin, minocycline, methyldopa, infliximab, statins.

— Positive ANA/ASMA, hypergammaglobulinemia; may need steroids; usually does not recur after drug withdrawal (unlike true AIH).

— Anabolic steroids → hepatic adenomas and HCC.

— OCPs → hepatic adenoma (rupture risk if >5 cm).

Acute liver failure (ALF):

Chronic DILI (~10–20% of cases):

Vanishing bile duct syndrome:

Steatohepatitis / fibrosis:

Nodular regenerative hyperplasia and sinusoidal obstruction syndrome:

Drug-induced autoimmune hepatitis:

Carcinogenic potential:

Key distinction: Chronic DILI is defined by persistent abnormalities 6 months after drug withdrawal; "delayed onset" DILI (drug-induced injury appearing weeks after stopping) is different — amox-clav classically shows this.

Board pearl: A patient with persistent jaundice and ductopenia on biopsy after antibiotic exposure has vanishing bile duct syndrome — counsel on transplant possibility and chronic management.

When to Escalate Care

— Bilirubin >2.5 mg/dL.

— INR ≥1.5.

— ALT/AST >10× ULN.

— Symptoms: vomiting, dehydration, anorexia preventing oral intake.

— Suspicion of hypersensitivity/DRESS (admit for steroids, monitoring).

— Patient unable to reliably stop drug or follow up.

— Any encephalopathy (grade I–II warrants close monitoring; III–IV mandates ICU).

— Worsening INR despite drug cessation.

— Hypoglycemia, hypotension, metabolic acidosis, rising lactate.

— Renal failure or oliguria.

— Hypoxemia or aspiration risk.

— Initiate early contact (don't wait for King's Criteria to be met).

— Acute liver failure (encephalopathy + INR ≥1.5).

— Rapidly rising bilirubin and INR despite supportive care.

— Hy's law–positive injury with worsening trajectory.

— Idiosyncratic DILI with bilirubin >17.5 or INR >3.5.

— Hepatology: any moderate–severe DILI, ambiguous diagnosis, chronic DILI, biopsy decisions.

— Toxicology / Poison Control: all APAP and mushroom ingestions.

— Dermatology: suspected DRESS/SJS overlap.

— Oncology: checkpoint inhibitor hepatitis management.

— Infectious disease: TB therapy reintroduction after hepatotoxicity, viral hepatitis exclusion.

— Pharmacy: medication reconciliation, identification of culprit drug, drug-drug interactions.

Outpatient → Hospital admission:

Hospital floor → ICU:

Hospital → Transplant center transfer:

Specialist consultations:

CCS pearl: On a CCS case of suspected APAP overdose with worsening INR at 24–48 h, order: ICU transfer, hepatology consult, transplant center contact, NAC continuation, frequent INR/glucose/ammonia checks, and head CT if mental status worsens (rule out cerebral edema or bleed). Advancing the clock without these orders loses points.

Step 3 management: The decision to transfer to a transplant center should be made when ALF is anticipated, not when it is established — early transfer saves lives and is the high-yield management answer.

Key Differentials — Other Hepatocellular Causes

— Hepatitis A: acute, often self-limited; fecal-oral; HAV IgM positive.

— Hepatitis B: acute (anti-HBc IgM, HBsAg+) vs. chronic flare (reactivation with rituximab, chemo); always check HBV serologies before immunosuppression.

— Hepatitis C: acute rare; chronic asymptomatic — HCV antibody + HCV RNA.

— Hepatitis E: consider in pregnancy (high mortality), travelers, immunocompromised, older men; HEV IgM.

— HSV, CMV, EBV: rare but consider in immunocompromised, pregnancy, or with atypical lymphocytosis.

— Young women, hypergammaglobulinemia, ANA/ASMA+, IgG↑.

— Can be triggered by drugs (nitrofurantoin, minocycline) — distinguishing AIH vs. drug-induced AIH may require biopsy and observation off therapy.

— <40 years old, hemolytic anemia + acute hepatitis, ALP low, bilirubin high, ratio ALP/bilirubin <4; low ceruloplasmin, high urinary copper.

— Massive transient ALT/AST rise (>1000) with rapid LDH elevation and quick normalization after hemodynamic recovery.

— Setting: hypotension, heart failure, sepsis.

— Hepatic vein thrombosis; RUQ pain, hepatomegaly, ascites; Doppler US diagnostic.

— Heavy alcohol use, AST:ALT >2:1, AST rarely >300, bilirubin elevated; Maddrey discriminant function for severity.

— Look for elevated CK, history of exertion or environment.

Viral hepatitis (must always exclude):

Autoimmune hepatitis:

Wilson disease:

Ischemic hepatitis ("shock liver"):

Budd-Chiari syndrome:

Acute alcoholic hepatitis:

Heat stroke, rhabdomyolysis-related transaminitis:

Key distinction: AST:ALT ratio >2 with AST <300 suggests alcoholic hepatitis; AST/ALT >5000 with rapid LDH spike suggests ischemic hepatitis; ALT >1000 with detectable APAP and history suggests APAP toxicity. The pattern often reveals the diagnosis before serologies return.

Board pearl: Always check HBV serologies before starting any immunosuppression or chemotherapy — reactivation hepatitis from rituximab is preventable with prophylactic entecavir/tenofovir.

Key Differentials — Cholestatic and Other Causes

— Choledocholithiasis: RUQ pain, fever, jaundice (Charcot triad → cholangitis); dilated CBD on US; MRCP/ERCP.

— Pancreatic head malignancy: painless jaundice, weight loss, palpable gallbladder (Courvoisier sign).

— Cholangiocarcinoma, ampullary tumor.

— Mirizzi syndrome.

— Primary biliary cholangitis (PBC): middle-aged women, fatigue, pruritus, AMA+, IgM↑; treat with UDCA.

— Primary sclerosing cholangitis (PSC): young men, IBD association, beaded ducts on MRCP, p-ANCA+.

— IgG4-related sclerosing cholangitis: mimics PSC; responds to steroids.

— Cholestasis of sepsis: total bilirubin >10 with disproportionately mild ALT/ALP rise in critically ill patients.

— Granulomatous: sarcoidosis, TB, fungal — also caused by drugs (allopurinol, sulfonamides, phenytoin).

— Lymphoma, metastatic disease, amyloidosis.

— Hemochromatosis: high ferritin, transferrin saturation >45%, HFE mutation.

— Alpha-1 antitrypsin deficiency: low A1AT level, ZZ phenotype.

— Wilson disease.

— NAFLD/NASH: mild ALT rise in metabolic syndrome.

— Congestive hepatopathy: right heart failure, ALP↑, mild bilirubin↑, distended IVC on US.

— HELLP, AFLP, intrahepatic cholestasis of pregnancy, hyperemesis gravidarum.

— Long-term TPN in adults and infants; manage with cycled TPN, fish-oil-based lipids, enteral feeding.

Extrahepatic biliary obstruction:

Intrahepatic cholestatic conditions:

Infiltrative liver disease:

Metabolic and genetic:

Cardiac:

Pregnancy-specific (covered in chunk 10):

Total parenteral nutrition (TPN)–associated cholestasis:

Step 3 management: A patient with cholestatic LFTs and dilated CBD on US needs MRCP or ERCP, not a DILI causality assessment — never miss obstructive jaundice. Pursue imaging first when ALP-predominant pattern is found.

Key distinction: AMA+ middle-aged woman with pruritus and cholestasis = PBC, not DILI; do not stop her statin reflexively. Coexistence is possible but PBC has a defined treatment path with UDCA.

Secondary Prevention, Discharge Planning, and Long-Term Care

— Add culprit drug (and entire drug class, where appropriate) to allergy/adverse reaction list in the EHR with reaction type ("DILI — hepatocellular injury").

— Cross-class warnings: amoxicillin-clavulanate DILI → avoid future amox-clav; penicillin alone usually tolerated.

— Statin DILI → may attempt alternate statin at low dose after recovery, with monitoring.

— Halothane DILI → avoid all halogenated anesthetics for life.

— Patient wallet card or MedicAlert bracelet recommended for serious reactions.

— Continue UDCA (13–15 mg/kg/day) if cholestatic pattern persists.

— Cholestyramine for pruritus, taken 1 h before or 4 h after other drugs.

— Vitamin K, vitamin D supplementation if cholestasis prolonged (fat-soluble vitamin deficiency risk).

— Folate supplementation if on methotrexate elsewhere.

— Avoid acetaminophen >2 g/day until recovery; counsel against NSAIDs.

— Alcohol abstinence during recovery; long-term limits per AUDIT.

— Avoid herbal supplements, weight-loss products, body-building powders.

— Hepatitis A and B vaccination if not immune (especially if chronic liver disease unmasked).

— Weight management, treat metabolic syndrome (NAFLD overlap).

— In general, do not rechallenge — recurrence risk and severity increase.

— Exceptions only for essential drugs (TB, HIV, malignancy) under specialist guidance and graded reintroduction.

— HAV and HBV in non-immune patients.

— Annual influenza, pneumococcal per chronic liver disease schedule if persistent injury.

— Report serious DILI to FDA MedWatch to support pharmacovigilance.

Drug avoidance documentation:

Discharge medications:

Lifestyle counseling:

Drug rechallenge counseling:

Vaccinations:

Reporting:

Step 3 management: A patient recovered from amox-clav DILI being seen for new UTI months later — order TMP-SMX or nitrofurantoin (avoiding amox-clav), counsel on lifetime avoidance, and reconfirm allergy documentation. This longitudinal management decision is a classic Step 3 testing pattern.

Board pearl: The FDA MedWatch report is the patient-safety answer when asked "what is the next best step after diagnosing serious DILI to a marketed drug?"

Follow-Up, Monitoring, and Counseling

— Mild outpatient DILI: LFTs at 1 week, 2 weeks, 4 weeks; expect normalization within 4–8 weeks for hepatocellular pattern, longer (up to 6 months) for cholestatic.

— Moderate inpatient DILI: daily LFTs + INR during admission; weekly until normal; then monthly until 3 months.

— If not normalized by 6 months → diagnose chronic DILI; reassess with imaging, autoimmune markers, consider biopsy.

— Isoniazid (INH): baseline LFTs in high-risk; monthly clinical assessment; LFTs only if symptomatic or risk factors. Stop if ALT >3× ULN with symptoms or >5× ULN asymptomatic.

— Methotrexate: baseline LFTs, then every 1–3 months. Cumulative dose monitoring with non-invasive fibrosis assessment (FibroScan) every 1–2 years.

— Statins: baseline LFTs; no routine monitoring needed; check if symptoms.

— Amiodarone: LFTs every 6 months.

— Valproate: LFTs at baseline, every 1–3 months in first year, especially in children.

— Tolvaptan, terbinafine, ketoconazole: specific monitoring schedules apply.

— Checkpoint inhibitors: LFTs before each cycle.

— Anti-TB therapy: LFTs every 2–4 weeks in high-risk; monthly clinical screening in others.

— Recognize early symptoms: fatigue, RUQ pain, jaundice, dark urine, pale stools, pruritus, nausea.

— Avoid alcohol throughout treatment with hepatotoxic drugs.

— Limit acetaminophen to ≤2 g/day in patients with chronic liver disease.

— Disclose all herbal supplements at every visit.

— Carry medication list with documented DILI agents.

— HAV/HBV vaccination, influenza, pneumococcal.

— Screen for HCC in those with progression to cirrhosis (US ± AFP every 6 months).

Monitoring schedule:

Targeted monitoring during certain therapies (board-relevant):

Counseling points:

Vaccinations and health maintenance:

CCS pearl: When you advance the simulated clock 4 weeks after stopping the drug, order "follow-up LFT panel" and "office visit" — this hits the value-based-care follow-up flag the case scoring rewards.

Step 3 management: The Step 3 follow-up answer for any drug initiation with hepatotoxic potential is "baseline LFTs and recheck at the guideline-specified interval" — never "no monitoring needed" if the drug is on the watchlist.

Ethical, Legal, and Patient Safety Considerations

— Drugs with known hepatotoxicity require disclosure of risk before initiation — methotrexate, amiodarone, isoniazid, valproate, ICIs, statins.

— Document discussion of monitoring plan and warning symptoms.

— Special consent for high-risk uses (e.g., methotrexate in non-malignant disease) often includes alcohol abstinence agreements.

— Serious or unexpected DILI reactions should be reported to FDA MedWatch — voluntary for clinicians but expected practice; pharmacies and manufacturers have mandatory reporting.

— Suspected pediatric or vulnerable-adult abuse from intentional poisoning requires Child/Adult Protective Services notification per state law.

— Suicide attempts with APAP overdose: report per institutional policy, place on safety hold pending psychiatric evaluation, do not discharge from ED without psychiatric clearance.

— DILI patients are at high risk for inadvertent rechallenge during care transitions (ED → admission → discharge → primary care → specialist).

— Use medication reconciliation at every handoff; update allergies in EHR; communicate to PCP and pharmacy.

— A culprit drug listed only as "intolerance" rather than "adverse reaction — DILI" risks re-prescription. Specify the reaction type in the chart.

— In intentional overdose (suicide attempt), maintain confidentiality balanced against safety; psychiatric hold (varies by state) when imminent risk.

— Substance use disclosure: protected but documentation needed for care.

— TB therapy hepatotoxicity may impact employment of healthcare workers; ensure occupational health involvement.

— Discuss return-to-work timing with patients in jaundice resolution phase.

— Failure to monitor LFTs per guideline (e.g., methotrexate) is a documented liability risk.

— Failure to document drug-allergy reaction type leading to rechallenge is a reportable patient safety event.

Informed consent:

Mandatory and recommended reporting:

Transition-of-care risks:

Confidentiality vs. duty to warn:

Workplace and disability:

Liability and product safety:

Key distinction: "Allergy" and "intolerance" are not interchangeable in the EHR — DILI is a serious adverse reaction, not an "intolerance." Mislabeling causes rechallenge.

Step 3 management: After an APAP suicide attempt with hepatic recovery, do not discharge without psychiatric evaluation, suicide-risk assessment, lethal-means counseling, and arranged outpatient mental health follow-up — these are required patient safety steps.

High-Yield Associations and Rapid-Fire Facts

— Amoxicillin-clavulanate (#1 idiosyncratic), isoniazid, nitrofurantoin, TMP-SMX, methotrexate, allopurinol, statins, NSAIDs, valproate, herbals (especially body-building/weight-loss).

— Hepatocellular: APAP, isoniazid, statins, methyldopa, ketoconazole, NSAIDs, troglitazone.

— Cholestatic: amox-clav, erythromycin estolate, chlorpromazine, anabolic steroids, OCPs, terbinafine.

— Mixed: phenytoin, sulfonamides, carbamazepine.

— Steatosis: valproate, tetracycline, amiodarone, nucleoside RTIs, tamoxifen.

— Granulomas: allopurinol, phenytoin, sulfonamides, hydralazine, quinidine.

— Autoimmune-like: nitrofurantoin, minocycline, methyldopa, statins, infliximab.

— Vanishing bile duct: amox-clav, chlorpromazine, flucloxacillin.

— Sinusoidal obstruction: azathioprine, oxaliplatin, busulfan.

— Adenomas/HCC: anabolic steroids, OCPs.

— Hy's law: ALT >3× ULN + bilirubin >2× ULN → ~10% mortality.

— King's College APAP: pH <7.3 or triad (INR>6.5, Cr>3.4, grade III–IV HE).

— APAP toxic dose: >7.5 g acute or >4 g/day chronic with risk factors.

— Rumack-Matthew line starts at 150 µg/mL at 4 h.

— NAC 21-h IV protocol: 150 → 50 → 100 mg/kg.

— Chronic DILI: persistence >6 months.

— Flucloxacillin — B*57:01.

— Amox-clav — DRB1*15:01.

— Minocycline — B*35:02.

— Terbinafine — A*33:01.

— Rituximab (highest risk), chemo, corticosteroids, TNF inhibitors. Screen all with HBsAg, anti-HBc.

— Chronic alcohol (induces CYP2E1), fasting, malnutrition, INH coadministration → lower toxic threshold.

Most common drugs causing DILI in US registries:

Pattern-drug pairings:

Key numbers:

HLA associations:

Triggers of HBV reactivation:

APAP risk modifiers:

Board pearl: "Patient on bodybuilding supplement with jaundice + bilirubin 25 + normal ALT" = anabolic steroid bland cholestasis. Treat with cessation and pruritus control; eventual recovery expected.

Board Question Stem Patterns

— 22-yr-old after suicide attempt, ingestion 6 h ago, APAP level above treatment line. → Start IV NAC immediately, psychiatric evaluation, do not discharge from ED. Trick: nomogram only valid for single acute ingestion at known time.

— Middle-aged patient with jaundice 3 weeks after completing amox-clav course; ALP ↑↑, ALT modestly ↑, bilirubin 5. → Stop drug (already done), supportive care, document allergy, expect slow recovery. Distractor: order ERCP — wrong unless dilated ducts.

— Patient 2 months into LTBI therapy with nausea and ALT 250. → Stop INH, recheck LFTs, evaluate for alternative cause. Reintroduce only after normalization with monitoring.

— ALT 600, bilirubin 4, ALP 200, INR 1.3 on drug X. → Hospitalize, hepatology consult, monitor for ALF.

— Phenytoin started 4 weeks ago; fever, rash, eosinophilia, ALT 400, lymphadenopathy. → Stop phenytoin, systemic corticosteroids, supportive care. Cross-reactivity with carbamazepine, lamotrigine, phenobarbital.

— 28-yr-old male with severe pruritus, bilirubin 28, ALP 250, ALT 60 — uses "supplements." → Anabolic steroid DILI; stop, UDCA, pruritus management.

— Mild ALT rise (1.5× ULN) on atorvastatin in patient with NAFLD. → Continue statin, monitor — do not discontinue.

— 3rd-trimester pruritus, bile acids elevated, ALT mildly elevated. → Intrahepatic cholestasis of pregnancy — UDCA, deliver at 36–37 weeks. Not DILI.

— Melanoma patient on ipilimumab/nivolumab with ALT 500. → Grade 3 hepatitis; hold ICI, methylprednisolone 1–2 mg/kg; do not give infliximab.

— After DILI, patient needs same drug class for essential indication. → Avoid rechallenge unless life-saving; use alternate agent or graded reintroduction under specialist.

Stem 1 — Acetaminophen overdose:

Stem 2 — Amox-clav cholestatic DILI:

Stem 3 — Isoniazid hepatotoxicity:

Stem 4 — Hy's law identification:

Stem 5 — DRESS:

Stem 6 — Bodybuilder cholestasis:

Stem 7 — Statin "intolerance":

Stem 8 — Pregnancy:

Stem 9 — ICI hepatitis:

Stem 10 — Rechallenge question:

Board pearl: When the stem includes "herbal supplement" or "bodybuilding product," the answer is almost always DILI — even if the patient denies taking medications.

One-Line Recap

Core teaching point: Drug-induced liver injury is a diagnosis of exclusion built on three pillars — recognize the pattern (hepatocellular, cholestatic, or mixed via R-value), exclude viral/autoimmune/obstructive mimics, and stop the offending drug while supporting the patient and watching for acute liver failure markers (Hy's law, encephalopathy, rising INR) that mandate transplant center transfer.

— R-value categorizes injury: ≥5 hepatocellular (APAP, INH, statins); ≤2 cholestatic (amox-clav, anabolic steroids); 2–5 mixed (phenytoin, sulfa). Always calculate at presentation to anchor your differential and prognosis.

— Hy's law (ALT >3× ULN + bilirubin >2× ULN without cholestasis) predicts ~10% mortality in idiosyncratic DILI — triggers hospitalization, hepatology consult, and consideration of transplant center notification before deterioration.

— Acetaminophen toxicity is the leading cause of US ALF: give NAC empirically and early, use Rumack-Matthew only for single acute ingestion at known time, and apply King's College Criteria (pH <7.3 or triad of INR>6.5 + Cr>3.4 + grade III/IV encephalopathy) to identify transplant candidates.

— Stop the drug, document the reaction type as DILI (not "intolerance"), report serious cases to FDA MedWatch, vaccinate against HAV/HBV, monitor LFTs to normalization, and avoid rechallenge — these are the longitudinal Step 3 management actions that differentiate adequate care from exam-correct care.

High-yield recap bullets:

Step 3 management: The exam-correct answer for nearly every DILI scenario is the same triad — stop the drug, support the patient, and arrange the right level of care and follow-up — and the wrong answers usually involve heroic pharmacology, unnecessary imaging, or rechallenging the culprit drug.