Drug-Induced Liver Injury Patterns: Hepatocellular vs. Cholestatic
The pattern of drug-induced liver injury is determined by the ALT/ALP ratio: hepatocellular injury (ALT/ALP ratio ≥5) is caused by drugs like acetaminophen, isoniazid, statins, and herbal medications, while cholestatic injury (ALT/ALP ratio ≤2) is classically caused by chlorpromazine, amoxicillin-clavulanate, and anabolic steroids. 1, 2
Biochemical Classification
The international consensus defines three patterns of DILI based on the ratio (R) of ALT to ALP, both expressed as multiples of upper limit of normal (ULN): 1, 2
- Hepatocellular injury: R ≥5 (isolated ALT >2× ULN or ALT/ALP ratio >5)
- Cholestatic injury: R ≤2 (isolated ALP >2× ULN or ALT/ALP ratio <2)
- Mixed injury: R between 2-5
Hepatocellular Pattern Drugs
Hepatocellular injury is the predominant form of DILI, accounting for approximately 60-70% of cases. 1, 3 This pattern is characterized by elevated transaminases reflecting direct hepatocyte damage with necrosis or steatosis. 4
Common Hepatocellular DILI Culprits:
- Acetaminophen (dose-dependent hepatotoxin causing acute necrosis) 5, 6
- Isoniazid (idiosyncratic hepatocellular injury)
- Statins (predominantly hepatocellular pattern, though can rarely cause cholestatic injury) 7
- Herbal medications and traditional preparations (more commonly hepatocellular than prescription drugs, with higher AST/ALT elevations) 3
- Minocycline (hepatocellular pattern with autoimmune features) 5, 8
- Doxycycline (rare cause, short latency period, hepatocellular pattern) 9
- Methotrexate (can produce hepatic fibrosis with chronic use) 5
- Azathioprine (highest estimated incidence among common drugs at 1:349-2329 prescriptions) 8
Cholestatic Pattern Drugs
Cholestatic DILI represents 20-40% of all DILI cases and has a better prognosis than hepatocellular injury, though recovery is typically slower. 1, 10 Cholestatic injury results from either inhibition of hepatocellular bile transporters or inflammatory/hypersensitivity reactions at the bile duct level. 1
Common Cholestatic DILI Culprits:
- Chlorpromazine (prototype drug causing prolonged cholestasis >6 months; can cause vanishing bile duct syndrome leading to permanent liver damage) 1
- Amoxicillin-clavulanate (most common antibiotic cause of DILI; cholestatic pattern; estimated incidence 1:1000-2400 prescriptions) 8
- Anabolic steroids (C-17 alkylated steroids are indirect cholestatic hepatotoxins) 4
- Contraceptive steroids (indirect cholestatic mechanism) 4
- Flucloxacillin (cholestatic hepatitis often with prolonged cholestasis and vanishing bile duct syndrome) 5
- Nitrofurantoin (estimated incidence approximately 1:1000-2400 prescriptions) 8
Clinical Implications and Prognosis
Drug-induced cholestatic injury generally has better outcomes than hepatocellular injury, but the time course for improvement is typically slower. 1, 10 Blood tests usually normalize within 3 months after drug withdrawal for cholestatic injury, compared to faster resolution with hepatocellular patterns. 1
Important Caveats:
- Cholestatic DILI onset typically occurs 2-12 weeks after drug initiation but may occur after one year, whereas hepatocellular DILI typically occurs 2-24 weeks after starting the drug. 10
- Older patients (≥60 years) are more prone to cholestatic DILI, comprising up to 61% of cases in this age group. 10
- Vanishing bile duct syndrome is a rare but serious complication of cholestatic DILI that can progress to biliary cirrhosis and permanent liver damage. 1, 10, 1
- Herbal medications and traditional preparations induce more hepatocellular DILI with higher AST/ALT elevations compared to prescription medications. 3