Acute Liver Failure

Clinical Snapshot

Acute liver failure (ALF) is defined as coagulopathy — an international normalized ratio (INR) of 1.5 or greater — together with any degree of hepatic encephalopathy, occurring within 26 weeks of the onset of illness in a patient with no evidence of pre-existing cirrhosis.^[1] A small number of conditions are recognized exceptions to the "no pre-existing cirrhosis" rule because they can present as ALF on top of previously unrecognized chronic liver disease: Wilson disease, reactivation of chronic hepatitis B, and autoimmune hepatitis.^[2] ALF is further described by the interval between jaundice onset and encephalopathy onset — hyperacute (0-7 days; classically acetaminophen, ischemic hepatitis, or hepatitis A/E), acute (8-28 days), and subacute (29 days to 26 weeks; classically idiosyncratic drug-induced liver injury, seronegative/indeterminate hepatitis, or Wilson disease) — a distinction that matters because hyperacute presentations carry a higher risk of cerebral edema but a better chance of spontaneous (transplant-free) recovery, while subacute presentations carry a lower cerebral edema risk but a worse chance of spontaneous recovery.^[3] Acetaminophen (paracetamol) toxicity is the single leading cause of ALF in North America, and idiosyncratic drug-induced liver injury (DILI) — most often from antituberculous therapy, anticonvulsants, certain antibiotics, or herbal/dietary supplements — is one of the next most common identifiable causes, which places pharmacists in a genuinely front-line position for both recognizing an emerging case and directing its specific antidotal treatment.^[4]

Recognize the Condition

Yellow discoloration of the sclera (scleral icterus) in a child with jaundice

Scleral icterus — yellowing of the sclera — in a child with jaundice from hemolytic anemia; the sclera often shows visible yellowing before skin discoloration becomes obvious, making it a key early sign to look for on exam. (Sab3el3eish, CC BY 3.0, Wikimedia Commons)

Typical evolution

ALF typically begins with a nonspecific prodrome — nausea, anorexia, malaise, right upper quadrant discomfort — that is easy to dismiss, followed by jaundice, and then by the two findings that define the syndrome: coagulopathy (easy bruising, mucosal bleeding, oozing from venipuncture sites) and hepatic encephalopathy (from subtle personality change through to coma). The degree of aminotransferase elevation does not reliably predict severity or outcome — synthetic function (INR) and mental status are what determine severity, not how high ALT/AST climbed.

Hepatic encephalopathy grading (West Haven criteria)

Grade	Mental status	Neuromuscular findings
I	Trivial lack of awareness, mild euphoria or anxiety, shortened attention span	Mild incoordination; asterixis usually absent or barely detectable
II	Lethargy or apathy, mild disorientation for time or place, subtle personality change, inappropriate behaviour	Asterixis present — this marks the transition to overt encephalopathy
III	Somnolence to semi-stupor but responsive to verbal stimuli, marked confusion, gross disorientation	Asterixis usually still present; increased muscle tone, hyperreflexia
IV	Coma, unresponsive to verbal or noxious stimuli	Asterixis no longer elicitable (patient cannot sustain the posture); decorticate or decerebrate posturing may be seen

Grade III-IV encephalopathy is the threshold at which cerebral edema and intracranial hypertension become a real, immediate risk — this is the point at which airway protection, ICU-level neuro-monitoring, and active management of intracranial pressure become urgent (see Red Flags & Refer and Choose Initial Treatment).^[1]

Signs of evolving cerebral edema / raised intracranial pressure

Systemic hypertension with bradycardia, abnormal pupillary responses, decorticate/decerebrate posturing, and papilledema can all indicate rising intracranial pressure in a patient with grade III-IV encephalopathy — a late-stage, life-threatening development that needs immediate escalation rather than routine reassessment.

Risk Factors

Acetaminophen-induced ALF

Intentional single large overdose.
"Therapeutic misadventure" — repeated supratherapeutic dosing over days, often from combination opioid-acetaminophen products taken for genuine pain, or from stacking multiple acetaminophen-containing products without realizing it — is a distinct and easily missed risk pattern; it does not fit the single-ingestion Rumack-Matthew nomogram (see Assessment & Diagnosis).
Chronic alcohol use, malnutrition, or a fasting/low-glycogen state — all lower glutathione stores and increase susceptibility to hepatotoxicity at doses that would otherwise be considered safe.
Concurrent use of other CYP2E1-inducing or hepatotoxic agents.

Idiosyncratic drug-induced liver injury (DILI)

Antituberculous therapy — isoniazid, alone or combined with rifampin, is one of the most commonly implicated agents; risk rises with age, alcohol use, and slow-acetylator genotype.
Anticonvulsants — valproate carries a particular risk of severe, sometimes fatal hepatotoxicity, highest in young children and in those with an underlying mitochondrial disorder.
Antibiotics — amoxicillin-clavulanate is among the most frequently implicated drugs in DILI registries generally (though its liver injury is more often cholestatic than fulminant); nitrofurantoin and certain sulfonamides are other recognized culprits.
Herbal and dietary supplements — a genuinely underappreciated and under-reported cause; bodybuilding/anabolic supplements, weight-loss products, and certain "green tea extract" or kava-containing products are specifically implicated.^[4]
Polypharmacy and genetic susceptibility (specific HLA haplotypes are increasingly recognized as risk markers for particular drugs).
Pre-existing chronic liver disease, which both increases DILI risk and increases the severity of a superimposed episode.

Other causes and their risk factors

Viral hepatitis A, B, or E (hepatitis E particularly in pregnancy and in those exposed to undercooked pork/game).
Autoimmune hepatitis — can present acutely, more often in women.
Ischemic hepatitis ("shock liver") — recent hypotension, cardiac arrest, or severe heart failure.
Wilson disease — consider specifically in patients under 40, especially with a low alkaline phosphatase relative to bilirubin and a Coombs-negative hemolytic anemia.
Acute fatty liver of pregnancy or HELLP syndrome — third-trimester pregnancy.
Amanita phalloides and related mushroom ingestion.
Budd-Chiari syndrome (hepatic venous outflow obstruction) — underlying prothrombotic states.
In up to about 15% of cases despite full work-up, no cause is ever identified (indeterminate/seronegative ALF).

Red Flags & Refer

Meeting the diagnostic definition of ALF — coagulopathy (INR ≥1.5) plus any hepatic encephalopathy — is itself the red flag. Contact a liver transplant centre immediately once this definition is met; do not wait for further deterioration, and do not wait for King's College Criteria to be positive before making first contact.^[1]

Grade III-IV hepatic encephalopathy, or any sign of evolving cerebral edema (hypertension with bradycardia, abnormal pupils, posturing) — emergency, needs airway protection and active intracranial-pressure management.
King's College Criteria met — the standard prognostic checklist for transplant listing.^[3]
Acetaminophen-induced ALF
Either arterial pH <7.30 (after adequate fluid resuscitation), or all three of: INR >6.5, serum creatinine >300 micromol/L (>3.4 mg/dL), and grade III-IV encephalopathy.
Non-acetaminophen ALF
Either INR >6.5, or at least 3 of: age <11 or >40 years; etiology is indeterminate, drug-induced, or seronegative hepatitis; jaundice-to-encephalopathy interval >7 days; INR >3.5; serum bilirubin >300 micromol/L (>17.5 mg/dL).
King's College Criteria have imperfect sensitivity — especially for non-acetaminophen causes — so a negative result does not rule out the need for transplantation; use it alongside, not instead of, ongoing hepatology/transplant-centre judgment.^[1]
Known or suspected acetaminophen overdose, or unexplained transaminitis with any acetaminophen exposure — start N-acetylcysteine without waiting for a full toxicology work-up (see Choose Initial Treatment).
Arterial ammonia markedly elevated (roughly >150-200 micromol/L) — associated with a materially higher risk of intracranial hypertension and cerebral herniation, and should heighten vigilance for neurologic deterioration even before encephalopathy is advanced.
Hypoglycemia — the failing liver loses its capacity for gluconeogenesis and glycogen storage; check glucose frequently and treat proactively rather than waiting for symptoms.
Pregnancy in the third trimester with new liver injury — assess urgently for acute fatty liver of pregnancy or HELLP syndrome, for which delivery is the definitive treatment.
Suspected Amanita phalloides (mushroom) poisoning — involve a poison control centre immediately; injury can be delayed 6-24 hours after ingestion, well after gastrointestinal symptoms have already settled.
A presentation that may not be ALF from hepatocyte injury at all — biliary obstruction or vascular occlusion (Budd-Chiari) need their own urgent, distinct work-up.

Assessment & Diagnosis

Confirming the diagnosis

INR ≥1.5 plus any grade of hepatic encephalopathy, illness duration <26 weeks, and no pre-existing cirrhosis (exceptions: Wilson disease, reactivated chronic hepatitis B, autoimmune hepatitis).^[1]
A history for exposures: every medication, supplement, and herbal/natural health product taken in the preceding weeks (dose, duration, timing), alcohol use, recent travel, mushroom foraging/ingestion, and any recent hypotensive or cardiac arrest event.

Core laboratory work-up

INR/PT, CBC, comprehensive metabolic panel (including glucose and creatinine), lactate, and arterial blood gas.
Venous or arterial ammonia — correlates only loosely with encephalopathy grade but a markedly elevated arterial level is a useful early warning for cerebral edema risk.
Acetaminophen level plus a full urine/serum toxicology screen for co-ingestants — check in every ALF patient regardless of the stated history, since unwitnessed or denied acetaminophen ingestion is common.
Viral serologies: anti-HAV IgM, HBsAg, anti-HBc IgM, anti-HCV/HCV RNA, anti-HEV (particularly in pregnancy or after relevant travel/exposure); consider HSV and VZV PCR in an unexplained case, especially if immunocompromised or pregnant.
Autoimmune markers (ANA, anti-smooth-muscle antibody, immunoglobulin levels), and in patients under 40, ceruloplasmin plus a 24-hour urine copper if Wilson disease is a possibility (a low alkaline phosphatase-to-bilirubin ratio and Coombs-negative hemolytic anemia are supportive clues).
Pregnancy test in every patient of childbearing potential.
Abdominal Doppler ultrasound to assess liver size and rule out hepatic venous outflow obstruction (Budd-Chiari) or biliary obstruction.
Liver biopsy is not required to make the diagnosis and is rarely pursued acutely given the coagulopathy; when histology is genuinely needed to resolve an unclear etiology, a transjugular (rather than percutaneous) approach is used specifically because of the bleeding risk.

Etiology at a glance

Category	Examples	Distinguishing clue
Acetaminophen	Single overdose or staggered supratherapeutic dosing	Markedly elevated ALT/AST (often >3,000-5,000 U/L), positive level or history
Idiosyncratic DILI	Isoniazid, valproate, amoxicillin-clavulanate, nitrofurantoin, herbal/supplement products	Temporal relationship to a new drug/supplement; a diagnosis of exclusion
Viral	Hepatitis A, B, E (rarely C alone); HSV/VZV in the immunocompromised or pregnant	Positive serology/PCR
Autoimmune hepatitis	—	Positive ANA/ASMA, elevated IgG, may respond to corticosteroids
Ischemic ("shock liver")	Recent hypotension, cardiac arrest, severe heart failure	Very high, rapidly falling transaminases; renal injury often coexists
Wilson disease	—	Age <40, low alkaline phosphatase relative to bilirubin, hemolytic anemia, low ceruloplasmin
Pregnancy-related	Acute fatty liver of pregnancy, HELLP	Third trimester; hypoglycemia and coagulopathy out of proportion (AFLP) or hemolysis/low platelets (HELLP)
Amanita mushroom poisoning	—	GI symptoms 6-24h after ingestion, followed by a latent period, then liver injury
Indeterminate	—	No cause found despite complete work-up (~15% of cases)

For suspected DILI specifically, the ACG guideline suggests a prognostic model combining MELD score, Charlson comorbidity index, and serum albumin to help estimate 6-month mortality and inform how urgently to escalate care.^[5]

Treatment Targets

Identify a specifically treatable cause promptly, and start N-acetylcysteine without delay whenever acetaminophen toxicity is possible.
Stop any hepatotoxic drug or supplement immediately once DILI is suspected — this is the single most important intervention in DILI.
Prevent and manage the major complications: cerebral edema, coagulopathy-related bleeding, infection, renal failure, and hypoglycemia.
Determine transplant candidacy early — via King's College Criteria and ongoing hepatology/transplant-centre judgment — rather than waiting for irreversible deterioration.
Provide ICU-level supportive care to maximize the chance of either spontaneous recovery or a successful bridge to transplantation.

Choose Initial Treatment

Two etiology-specific tracks, plus universal supportive care

Acetaminophen-induced ALF

N-acetylcysteine (NAC) is a genuine antidote — start immediately.

Idiosyncratic DILI

Stop the causative drug/supplement immediately; there is no specific antidote for most agents.

Every cause of ALF

ICU-level supportive care, cerebral-edema and coagulopathy management, and early transplant-centre contact apply regardless of etiology.

Direct treatment rule

Acetaminophen toxicity — N-acetylcysteine

Start immediately for known or suspected acetaminophen overdose, or unexplained transaminitis with any acetaminophen exposure — do not wait for a confirmatory level or a fully developed toxicology picture if the history is compelling.^[6]

For a single, acute, known-time ingestion, plot the 4-hour (or later) acetaminophen level on the Rumack-Matthew nomogram against time since ingestion to decide whether treatment is indicated.^[6]

The nomogram does not apply to staggered/repeated supratherapeutic ingestion, an unknown ingestion time, or an extended-release product — treat these using clinical judgment and a lower threshold (any detectable level with symptoms or abnormal LFTs, or a reported intake pattern consistent with a potentially toxic cumulative dose) rather than a single nomogram point.^[6]

Give NAC for the full course (see Drug Tables for exact IV and oral protocols); once ALF is present, continue NAC beyond the standard protocol duration until encephalopathy resolves, INR normalizes, or transplantation occurs — do not stop simply because the scheduled infusion time has elapsed.^[1]

Idiosyncratic DILI

Stop the suspected drug or supplement immediately — this is the single highest-yield intervention and applies before any other work-up is complete.^[4]

Consider corticosteroids only for a specific autoimmune-like or hypersensitivity DILI phenotype (features such as eosinophilia, rash, or a clinical picture resembling autoimmune hepatitis) — this is not a routine intervention for ordinary idiosyncratic DILI.^[5]

Do not rechallenge with the suspected agent to "confirm" the diagnosis — the risk of a more severe recurrent injury outweighs any diagnostic benefit.

N-acetylcysteine in non-acetaminophen ALF

Consider IV N-acetylcysteine even when acetaminophen is not the cause — a randomized trial found improved transplant-free survival with NAC specifically in patients with early-stage (grade I-II) encephalopathy from non-acetaminophen ALF, with no benefit demonstrated once encephalopathy was advanced (grade III-IV).^[7] Because NAC carries low risk, current guidance supports considering it broadly in non-acetaminophen ALF, particularly if identified early.^[1]

Cerebral edema / raised intracranial pressure — grade III-IV encephalopathy

Secure the airway (intubate for grade III-IV encephalopathy, both for airway protection and to allow controlled sedation/ventilation); elevate the head of bed 30 degrees; minimize unnecessary stimulation and noise.

Hypertonic saline to target a serum sodium of roughly 145-155 mmol/L is the mainstay for preventing/treating intracranial hypertension in this setting.

Mannitol bolus for an acute rise in intracranial pressure or acute neurologic deterioration, provided renal function and serum osmolality allow it.

Avoid routine prophylactic hyperventilation — reserve brief hyperventilation for impending herniation only, not as a standing strategy.

Use short-acting, minimally hepatically-dependent sedation (e.g., propofol, fentanyl) if sedation is required for ventilation, and avoid unnecessary benzodiazepines, which accumulate and can mask or worsen the neurologic exam (see Drug Tables).

Coagulopathy, infection, and metabolic support

Coagulopathy

Do not correct an elevated INR prophylactically — INR is a key prognostic and transplant-listing marker in ALF, and reflexively normalizing it removes the ability to track the patient's true trajectory.

Reserve vitamin K, fresh frozen plasma, cryoprecipitate, and platelets for active bleeding or immediately before an invasive procedure; recombinant factor VIIa is a reasonable alternative when a procedure is urgent and volume-sensitive.

Infection

ALF impairs innate immune function — keep a low threshold for surveillance cultures and empiric broad-spectrum antibiotics with any clinical deterioration or fever; some transplant centres use scheduled prophylactic antimicrobial regimens.

Renal support

Continuous renal replacement therapy is preferred over intermittent hemodialysis when renal support is needed, given better hemodynamic and intracranial-pressure stability.

Glucose

Check glucose frequently and treat proactively with a dextrose infusion — the failing liver loses both gluconeogenic capacity and glycogen reserve, and hypoglycemia can compound encephalopathy.

Etiology-specific therapy

Suspected HSV/VZV hepatitis (unexplained ALF with fever or coagulopathy out of proportion to the biochemical picture, especially if immunocompromised or pregnant): start empiric IV acyclovir while serology/PCR is pending.

Amanita phalloides poisoning: activated charcoal if within the early post-ingestion window; IV penicillin G and/or silibinin under toxicology/poison-control direction — no standardized regimen exists, so specialist direction is required.

Acute fatty liver of pregnancy or HELLP syndrome: expedite delivery — this is the definitive treatment, not a pharmacologic one.

Every etiology: contact the liver transplant centre as soon as the diagnostic definition of ALF is met — do not wait for King's College Criteria to become positive before making first contact.^[1]

Non-Pharmacologic Treatment

ICU-level monitoring for any patient with grade II or higher encephalopathy.
Head-of-bed elevation to 30 degrees and a low-stimulation environment once encephalopathy reaches grade III-IV.
Avoid unnecessary sedation — it masks the neurologic exam and can precipitate or worsen encephalopathy.
Maintain adequate nutrition — enteral feeding with protein intake of roughly 1.0-1.5 g/kg/day; protein restriction is outdated and not recommended, since it does not reliably improve encephalopathy and worsens nutritional status.
Gut decontamination for a large or recent ingestion: activated charcoal if within about 1-2 hours of ingestion (or later for an extended-release product or a co-ingestant that delays gastric emptying); whole bowel irrigation is an option for extended-release acetaminophen or a co-ingested enteric-coated/sustained-release product.
Avoid unnecessary invasive procedures given the coagulopathy; when a procedure is required, plan it around correction of coagulopathy rather than around routine correction beforehand.
Early and repeated communication with a liver transplant centre — this is itself a core part of management, not an afterthought once the patient has deteriorated.

Pharmacologic Treatment Options

Drug / intervention	Role	Dose / use	Important adverse effects	Teaching points
N-acetylcysteine, IV Preferred	Antidote for acetaminophen toxicity; consider in non-APAP ALF with early-grade encephalopathy	150 mg/kg over 60 min, then 50 mg/kg over 4h, then 100 mg/kg over 16h (300 mg/kg total over ~21h)	Anaphylactoid reaction (rash, flushing, bronchospasm) — slow the infusion and treat symptomatically; nausea	Start immediately on suspected overdose. Continue beyond the standard course once ALF is present, until encephalopathy resolves, INR normalizes, or transplant occurs.
N-acetylcysteine, oral Alternative	Antidote for acetaminophen toxicity when IV access/route is not preferred	Loading 140 mg/kg, then 70 mg/kg PO/NG every 4h for 17 doses (72h protocol)	Nausea, vomiting (dose-limiting), unpleasant odour/taste	An option when IV NAC is unavailable or not preferred; pretreat with an antiemetic if vomiting is a concern.
Vitamin K1 (phytonadione) Preferred	Coagulopathy — one-time empiric trial only	10 mg PO or IV once	Rare anaphylactoid reaction with IV administration — give slowly	A persistently elevated INR despite vitamin K reflects true synthetic liver failure, not a deficiency state — do not treat as a dosing failure; do not correct INR further outside active bleeding or a planned procedure.
Hypertonic saline (3%) Preferred	Prevention/treatment of cerebral edema, grade III-IV encephalopathy	Titrated to target serum sodium ~145-155 mmol/L	Hypernatremia, fluid overload	Mainstay of ICP management in ALF; requires ICU monitoring and frequent electrolyte checks.
Mannitol Alternative	Acute rise in intracranial pressure or acute neurologic deterioration	0.5-1 g/kg IV bolus	Hyperosmolality, renal injury with repeated dosing, fluid shifts	Confirm adequate renal function and serum osmolality before dosing; not a substitute for hypertonic saline as ongoing therapy.
Lactulose Special situation	Adjunct for lower-grade (I-II) hepatic encephalopathy	Titrated to 2-3 soft stools/day	Diarrhea, dehydration, electrolyte disturbance, bloating	Use cautiously — overzealous purging causing dehydration/electrolyte derangement can itself worsen encephalopathy. Evidence in ALF specifically is weaker than in chronic hepatic encephalopathy.
Acyclovir, IV Special situation	Empiric therapy for suspected HSV/VZV hepatitis	Per current product monograph, weight-based IV dosing	Renal impairment (crystal nephropathy) — ensure adequate hydration	Start empirically while HSV/VZV serology/PCR is pending in an unexplained ALF case, especially if immunocompromised or pregnant.

Special Populations

Pregnancy

Third-trimester liver injury needs urgent evaluation for acute fatty liver of pregnancy (AFLP) and HELLP syndrome, both of which can cause or mimic ALF — hypoglycemia and coagulopathy out of proportion to the degree of transaminase elevation point toward AFLP, while hemolysis, elevated liver enzymes, and low platelets point toward HELLP. Delivery is the definitive treatment for both and should not be delayed for further liver-specific work-up once either is suspected. Hepatitis E also carries a disproportionately severe course in pregnancy. N-acetylcysteine is considered safe in pregnancy for acetaminophen toxicity — the risk to the fetus from untreated maternal toxicity far outweighs any risk from NAC itself.

Pediatrics

The etiology distribution differs from adults: indeterminate/seronegative hepatitis and inherited metabolic disease are relatively more common causes in children, and acetaminophen and DILI are relatively less dominant than in adults, though still important. King's College Criteria were derived in and validated mainly for adults and perform less reliably in children — pediatric-specific prognostic scoring is used at specialized centres. NAC dosing is weight-based using the same mg/kg regimen as adults.

Renal impairment

N-acetylcysteine dosing does not require renal adjustment. Avoid other nephrotoxic drugs where possible. Continuous renal replacement therapy is preferred over intermittent hemodialysis if renal support is needed, given better hemodynamic and intracranial-pressure stability.

Obesity

Weight-based NAC dosing in a patient over roughly 100 kg should be capped or calculated using an adjusted body weight per current toxicology-consensus guidance, rather than dosed on actual body weight without limit — uncapped dosing in a larger patient increases nausea/vomiting and anaphylactoid reaction risk without added benefit.^[6]

Older adults

Reduced hepatic functional reserve and a higher burden of comorbidity both lower the threshold for early transplant-centre involvement and can affect ultimate transplant candidacy — involve the transplant team early rather than waiting to see whether an older patient "declares" a clearly poor trajectory.

Monitoring & Follow-Up

Neurologic/encephalopathy-grade checks at least every 1-2 hours in any patient with grade II or higher encephalopathy, or with any downward trend.
Serial INR, glucose, lactate, electrolytes, and renal function — frequency guided by severity and trend (as often as every few hours in a rapidly evolving case, less often once clearly stabilizing).
Serial ammonia is reasonable in a patient with evolving or worsening encephalopathy, recognizing its correlation with encephalopathy grade is imperfect.
Continue N-acetylcysteine and monitoring for acetaminophen-induced injury until acetaminophen is undetectable and INR/encephalopathy are clearly improving from their worst point, not simply until the scheduled infusion ends.
Low threshold for repeat cultures and clinical reassessment for infection at any sign of deterioration.
Invasive intracranial pressure monitoring is used selectively at specialized centres given its own bleeding risk in a coagulopathic patient; non-invasive approaches (e.g., optic nerve sheath diameter ultrasound, clinical/imaging assessment) are used more often as a lower-risk alternative.
Reassess transplant candidacy daily — King's College Criteria status can change quickly in either direction.

Treatment Failure / Next Step

Worsening INR, encephalopathy grade, or new signs of cerebral edema despite N-acetylcysteine and supportive care — escalate immediately to the transplant centre and expedite listing evaluation rather than continuing routine monitoring.
King's College Criteria met — expedite transplant listing; remember the criteria's imperfect sensitivity means a patient who does not meet them can still be deteriorating and warrants continued close involvement of the transplant team rather than reassurance.^[1]
Refractory intracranial hypertension despite hypertonic saline and mannitol — consider second-tier measures (e.g., targeted temperature management/mild hypothermia, or other specialist-directed interventions) under critical-care/hepatology direction; these are not first-line and should not be attempted outside a specialized setting.
Not a transplant candidate (irreversible multi-organ failure, or another absolute contraindication) — shift the goals-of-care conversation toward comfort-focused management rather than continuing maximal interventions indefinitely.
Etiology remains indeterminate despite a complete work-up — consider transjugular liver biopsy to help clarify diagnosis and guide any etiology-specific therapy (e.g., corticosteroids for an autoimmune-hepatitis-like picture) under specialist direction.

Common Errors to Avoid

Waiting for a confirmatory acetaminophen level, or for transaminases to become dramatically abnormal, before starting N-acetylcysteine — start based on a compelling ingestion history and treat while confirmatory results are pending.
Applying the Rumack-Matthew nomogram to a staggered/repeated-ingestion or unknown-timing overdose — the nomogram is only valid for a single, acute, known-time ingestion; use a lower, non-nomogram treatment threshold instead.^[6]
Stopping N-acetylcysteine at the end of the standard protocol duration in a patient who has already progressed to ALF — continue until encephalopathy resolves, INR normalizes, or transplantation occurs.
Correcting an elevated INR prophylactically with FFP or vitamin K outside of active bleeding or an imminent procedure — this destroys a key prognostic marker without a clinical benefit.
Treating a persistently elevated INR after a single vitamin K dose as a "dosing failure" rather than recognizing it as true synthetic liver failure and a red flag for urgent referral.
Missing chronic supratherapeutic acetaminophen dosing ("therapeutic misadventure") as a cause because the presentation doesn't look like a classic single overdose.
Failing to check an acetaminophen level in every ALF patient regardless of the stated history — unwitnessed or denied ingestion is common.
Rechallenging a patient with a suspected DILI-causing drug to "confirm" the diagnosis.
Missing Wilson disease in a young patient, or acute fatty liver of pregnancy/HELLP in a third-trimester patient, because the presentation was assumed to be viral or drug-induced by default.
Using benzodiazepines liberally for agitation in a patient with hepatic encephalopathy — they accumulate in liver failure and can precipitate or mask worsening encephalopathy (see Drug Tables).
Delaying first contact with a liver transplant centre until the patient has already deteriorated significantly — early contact is the default even when the patient ultimately does not need transplantation.

Clinical Decision Algorithm

Algorithm A — Recognizing and confirming acute liver failure

Jaundice, altered mentation, and/or bleeding/bruising in a patient with acute liver injury

Obtain INR, ammonia, glucose, acetaminophen level plus full toxicology screen, viral serologies, and a directed history (medications, supplements, alcohol, pregnancy status, mushroom ingestion)

INR ≥1.5 AND any grade of encephalopathy, illness <26 weeks, no pre-existing cirrhosis

Acute liver failure confirmed — contact liver transplant centre immediately, proceed to Algorithm B

Criteria not met

Manage as acute liver injury without failure — continue work-up and monitor closely for progression

Algorithm B — Etiology-directed initial treatment

ALF confirmed — determine most likely etiology

Acetaminophen toxicity known/suspected

Single known-time ingestion: apply Rumack-Matthew nomogram. Staggered/unknown timing: use non-nomogram threshold

Start N-acetylcysteine immediately; continue beyond standard duration while ALF persists

Idiosyncratic DILI suspected

Stop the causative drug/supplement immediately

Supportive care; consider corticosteroids only for an autoimmune-like/hypersensitivity phenotype

Other/indeterminate etiology

Etiology-specific therapy if identified (e.g., empiric IV acyclovir for suspected HSV/VZV, expedited delivery for AFLP/HELLP)

Consider IV N-acetylcysteine if encephalopathy is early-grade (I-II) — improves transplant-free survival even without acetaminophen involvement

Universal supportive care: avoid prophylactic INR correction, monitor glucose closely, low threshold for infection work-up, proceed to Algorithm C for encephalopathy management

Algorithm C — Hepatic encephalopathy grade-directed management

Grade hepatic encephalopathy (West Haven I-IV)

Grade I-II

Ward/step-down monitoring; consider lactulose cautiously; avoid sedatives; monitor for progression

Grade III-IV

ICU admission; intubate for airway protection; head of bed 30°; minimize stimulation

Hypertonic saline (target Na 145-155 mmol/L); mannitol bolus for acute ICP rise; avoid routine hyperventilation

Proceed to Algorithm D — assess King's College Criteria without delay

Algorithm D — King's College Criteria and transplant referral

Liver transplant centre already contacted (Algorithm A) — apply King's College Criteria

Acetaminophen-induced ALF

Arterial pH <7.30? OR all three of INR >6.5, creatinine >300 micromol/L, grade III-IV encephalopathy?

Non-acetaminophen ALF

INR >6.5? OR ≥3 of: age <11/>40, indeterminate/drug-induced/seronegative etiology, jaundice-to-coma interval >7 days, INR >3.5, bilirubin >300 micromol/L?

Either pathway

Criteria met

Expedite transplant listing evaluation

Criteria not met but clinical trajectory is worsening: criteria have imperfect sensitivity — continue close transplant-team involvement rather than reassurance

Drug Tables

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

N-acetylcysteine dosing protocols (acetaminophen toxicity, and consider in early-grade non-acetaminophen ALF)

Give with an antihistamine and slow the infusion rate for an anaphylactoid reaction (rash, flushing, bronchospasm, hypotension) rather than stopping treatment unless the reaction is severe.

Drug	Dosage	Adverse effects	Drug interactions	Comments
N-acetylcysteine, IV (traditional 3-bag/Prescott protocol)	1st infusion (loading): 150 mg/kg IV over 60 minutes 2nd infusion: 50 mg/kg IV over 4 hours 3rd infusion (maintenance): 100 mg/kg IV over 16 hours	Anaphylactoid reaction, nausea	None clinically significant at antidote doses	The most established regimen. A simplified 2-bag alternative (e.g., 200 mg/kg over 4h then 100 mg/kg over 16h) is used off-label at some centres and appears to reduce anaphylactoid reactions with similar efficacy, but is not yet the universal standard.^[6]
N-acetylcysteine, oral/enteral	Loading: 140 mg/kg PO/NG Maintenance: 70 mg/kg PO/NG every 4 hours for 17 doses	Nausea, vomiting (dose-limiting), unpleasant odour/taste	None clinically significant at antidote doses	72-hour protocol; an option when IV access is unavailable or unnecessary. Pretreat with an antiemetic if vomiting is a concern.^[6]
N-acetylcysteine, extended/maintenance dosing once ALF is present	Continued maintenance: 100 mg/kg IV over 16 hours, repeated as needed	Same as above	None clinically significant	Continue the maintenance infusion rate beyond the standard protocol until encephalopathy resolves, INR trends toward normal, or transplantation occurs — do not stop at the scheduled end time in a patient who has progressed to ALF.^[1]

Coagulopathy and cerebral edema management

Do not correct INR prophylactically outside active bleeding or an imminent procedure — it is a prognostic marker, not simply a lab value to normalize.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Vitamin K1 (phytonadione)	Dosing: 10 mg PO or IV once	Rare anaphylactoid reaction with IV administration	None clinically significant	One-time empiric trial is reasonable; a persistently elevated INR despite vitamin K indicates true synthetic failure, not a deficiency state. Avoid IM/SC administration given bleeding risk.
Mannitol	Dosing: 0.5-1 g/kg IV bolus	Hyperosmolality, renal injury with repeated dosing, fluid/electrolyte shifts	Additive nephrotoxicity with other nephrotoxic agents	For an acute rise in intracranial pressure or acute neurologic deterioration in grade III-IV encephalopathy; confirm renal function and serum osmolality before dosing.
Hypertonic saline (3% sodium chloride)	Dosing: Titrated infusion per institutional ICU protocol	Hypernatremia, fluid overload, central pontine myelinolysis if corrected too fast in the wrong direction	None clinically significant	Mainstay of intracranial-pressure management in ALF; titrate to a target serum sodium of roughly 145-155 mmol/L with ICU-level monitoring.

Common idiosyncratic DILI culprits pharmacists should recognize

A diagnosis of exclusion — stop the suspected agent immediately once DILI is suspected; do not wait for the full work-up to be complete.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Isoniazid	Dosing: Per current tuberculosis treatment protocol	Hepatotoxicity ranging from asymptomatic transaminase elevation to fulminant liver failure; peripheral neuropathy	Risk compounded when combined with rifampin; slow-acetylator (NAT2) genotype increases risk	One of the most commonly implicated antituberculous agents; risk increases with age and alcohol use. Stop immediately if transaminases rise significantly or symptoms develop.^[4]
Valproic acid / divalproex	Dosing: Per current epilepsy/mood-stabilizer dosing guidance	Hepatotoxicity, including rare fatal cases; hyperammonemia; pancreatitis	Risk increased with concurrent hepatotoxic agents	Risk is highest in young children and in those with an underlying mitochondrial disorder. Stop immediately if hepatotoxicity is suspected.^[4]
Amoxicillin / clavulanic acid	Dosing: Per current infection-specific dosing guidance	Hepatotoxicity, typically cholestatic and delayed (can appear 1-6 weeks after stopping the drug); more common in older adults and with repeated courses	None clinically significant for this effect	Among the most frequently implicated antibiotics in DILI registries generally; injury pattern is more often cholestatic than the fulminant pattern seen with acetaminophen.^[4]
Rifampin	Dosing: Per current tuberculosis treatment protocol	Hepatotoxicity, particularly in combination with isoniazid; harmless orange discolouration of body fluids	Potent CYP3A4/CYP enzyme inducer — reduces levels of many co-administered drugs	Monitor liver enzymes closely when combined with isoniazid for tuberculosis treatment.^[4]
Nitrofurantoin	Dosing: Per current urinary tract infection dosing guidance	Hepatotoxicity (acute or chronic/autoimmune-like with long-term use); pulmonary toxicity with prolonged use	None clinically significant for this effect	Chronic use carries a distinct autoimmune-hepatitis-like hepatotoxicity pattern — a good candidate for a corticosteroid trial if that phenotype is present.^[4]
Methotrexate	Dosing: Per current indication-specific dosing guidance	Hepatotoxicity (more often chronic fibrosis with long-term low-dose use than acute failure), myelosuppression	Increased toxicity with other antifolate or hepatotoxic agents; avoid concurrent alcohol	Acute liver failure from methotrexate is uncommon but reported, particularly with dosing errors (e.g., inadvertent daily rather than weekly dosing).^[4]
Herbal and dietary supplement products	—: Not applicable — identification and discontinuation is the intervention	Hepatotoxicity of variable pattern and severity, often under-recognized and under-reported by patients	Variable and often uncharacterized	Specifically implicated products include bodybuilding/anabolic supplements, weight-loss products, and certain concentrated green tea extract or kava-containing products. Always ask about supplement use directly — patients rarely volunteer it.^[4]^[5]

Medications to avoid or dose-adjust once liver failure is present

Impaired hepatic clearance, reduced protein binding from hypoalbuminemia, and the risk of masking or worsening encephalopathy all argue for a lower threshold to avoid or reduce these agents.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Diazepam, lorazepam, midazolam (benzodiazepines)	—: Avoid, or minimum effective dose only	Accumulation and prolonged sedation; can precipitate or mask worsening hepatic encephalopathy	Additive sedation with opioids and other CNS depressants	Avoid where possible; if sedation is unavoidable, use the lowest effective dose of a short-acting agent and reassess frequently.
Morphine, hydromorphone, fentanyl	—: Reduced dose, extended interval	Prolonged sedation and respiratory depression from reduced clearance	Additive sedation with benzodiazepines	Reduce the dose and extend the interval; fentanyl's short context-sensitive half-life makes it a reasonable choice when an opioid is required in the ICU setting.
Meperidine	—: Avoid	Accumulation of the neurotoxic metabolite normeperidine, causing tremor and seizures	Additive CNS toxicity with other agents	Avoid entirely in liver failure — the metabolite accumulation risk is disproportionate to its analgesic benefit.
Ibuprofen, naproxen (NSAIDs)	—: Avoid	GI bleeding risk (compounds existing coagulopathy), renal injury (worsens hepatorenal physiology)	Additive bleeding risk with existing coagulopathy	Avoid — the combination of coagulopathy and a tendency toward renal hypoperfusion makes NSAIDs a poor choice in ALF.
Acetaminophen (in a non-acetaminophen cause of ALF)	—: Avoid in active ALF	Further hepatotoxicity risk, though standard analgesic doses are tolerated by many patients with stable, mild chronic liver disease	None clinically significant at low dose	In active ALF, avoid regardless of etiology unless specifically directed by the treating hepatology team — the diagnostic and therapeutic confusion of introducing it outweighs its analgesic benefit.
Warfarin and other anticoagulants	—: Avoid initiating	Compounds an already deranged coagulation system, with unpredictable effect since INR is already elevated from liver disease itself	Unpredictable interaction with the baseline coagulopathy	Avoid starting; if a patient is already anticoagulated for an unrelated indication, discuss holding with the treating team given the baseline coagulopathy.
Amiodarone	—: Avoid initiating	Direct hepatotoxicity, and reduced clearance of other agents via CYP inhibition	Broad CYP interactions	Avoid initiating in ALF; itself a recognized (though uncommon) cause of drug-induced liver injury.
Clopidogrel	—: Reduced efficacy — reassess necessity	Reduced antiplatelet efficacy	Requires hepatic CYP2C19 activation to its active metabolite	Efficacy is reduced when hepatic activation capacity is impaired — discuss alternatives with the treating team if antiplatelet therapy is genuinely required.

Etiology-specific and adjunct therapies

Drug	Dosage	Adverse effects	Drug interactions	Comments
Acyclovir, IV	Dosing: Weight-based IV dosing per current product monograph	Renal impairment (crystal nephropathy) — ensure adequate hydration	None clinically significant	Start empirically for suspected HSV/VZV hepatitis (unexplained ALF, especially if immunocompromised or pregnant) while serology/PCR is pending.
Penicillin G	Dosing: Specialist-directed only	Hypersensitivity reactions; electrolyte load with high-dose IV potassium/sodium salts	None clinically significant at antidote doses	Used for suspected Amanita phalloides poisoning under toxicology/poison-control direction — no standardized regimen exists for this indication.
Lactulose	Dosing: Titrated to effect	Diarrhea, dehydration, electrolyte disturbance, bloating	None clinically significant	Reasonable adjunct for grade I-II encephalopathy; titrate to 2-3 soft stools/day and avoid overzealous purging, which can itself worsen encephalopathy through dehydration.

References

ACG Clinical Guideline: Acute Liver Failure Guidelines — American College of Gastroenterology (Shingina A, Mukhtar N, Wakim-Fleming J, Alqahtani S, Wong RJ, Limketkai BN, Larson AM, Grant L). Am J Gastroenterol 2023;118(7):1128-1153
AASLD Position Paper: The Management of Acute Liver Failure — Update 2011 — American Association for the Study of Liver Diseases (Lee WM, Stravitz RT, Larson AM). Hepatology 2012;55(3):965-967
Early indicators of prognosis in fulminant hepatic failure (King's College Criteria) — Gastroenterology (O'Grady JG, Alexander GJ, Hayllar KM, Williams R). Gastroenterology 1989;97(2):439-445
AASLD Practice Guidance on Drug, Herbal, and Dietary Supplement-Induced Liver Injury — American Association for the Study of Liver Diseases (Fontana RJ, Liou I, Reuben A, Suzuki A, Fiel MI, Lee W, Navarro V). Hepatology 2023;77(3):1036-1065
ACG Clinical Guideline: Diagnosis and Management of Idiosyncratic Drug-Induced Liver Injury — American College of Gastroenterology (Chalasani NP, Maddur H, Russo MW, Wong RJ, Reddy KR). Am J Gastroenterol 2021;116(5):878-898
Management of Acetaminophen Poisoning in the US and Canada: A Consensus Statement — America's Poison Centers, American Academy of Clinical Toxicology, American College of Medical Toxicology, and Canadian Association of Poison Control Centres (Dart RC, Mullins ME, Matoushek T, et al.). JAMA Netw Open 2023;6(8):e2327739
Intravenous N-acetylcysteine improves transplant-free survival in early stage non-acetaminophen acute liver failure — Gastroenterology (Lee WM, Hynan LS, Rossaro L, et al.; Acute Liver Failure Study Group). Gastroenterology 2009;137(3):856-864

Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.