Study Notes on Drug-Induced Liver Injury (DILI)

Overview of Drug-Induced Liver Injury (DILI)

  • Presenter: Nick Buckley

  • Focus: Epidemiology and diagnosis of drug-induced liver injury

  • Key Aspects Covered: Common causes, diagnostic principles, liver biomarkers

Epidemiology of Drug-Induced Liver Injury (DILI)

  • Definition: Drug-induced liver injury refers to liver damage resulting from medication use.

  • Diagnosis Challenges: Diagnosing DILI can be difficult, akin to diagnosing autoimmune diseases.

  • Importance of Awareness: Knowing common medications that cause liver injury is crucial for healthcare professionals.

    • Key Point: Inquire about medications used in cases of unexplained acute liver injury.

Common Medications Causing Liver Injury

  • Epidemiological Studies: Majority of the studies rely on case reviews to identify drug-induced liver injury.

  • Age Statistics:

    • Average Age of Patients: Around 50 years.

    • Implication: Higher average age of medication users in Australia (70-80 years) suggests missed diagnoses in older patients.

  • Mortality Rates:

    • Range: 5% to 10% mortality associated with DILI.

    • Chronic Issues: Some patients develop chronic liver problems.

  • Common Drug Categories Leading to DILI:

    • Antibiotics: Most prevalent cause of acute liver injury.

    • Psychotropic Drugs: Second most common.

    • Herbal and Dietary Supplements: Notable contributors.

    • Other Drugs: Cardiovascular agents and central nervous system drugs are less commonly implicated.%

Diagnosis of Drug-Induced Liver Injury

  • Clinical Suspicion:

    • Requirement: High clinical suspicion necessary for making a diagnosis of DILI.

    • Key Insight: "The eye cannot see what the mind is not looking for."

  • Timing of Onset:

    • Critical Element: The timing of liver injury in relation to drug exposure can indicate the cause.

      • Acute Toxic Reactions: Expected to occur quickly after first exposure.

      • Immune Reactions: Typically manifest 1-3 weeks after exposure.

      • Chronic Reactions (e.g., Methotrexate): Can take years to develop.

  • Biopsy Utilization: In some cases, liver biopsy can aid in diagnosis.

  • Other Causes of Liver Injury: Extensive differential diagnoses must be considered due to numerous conditions affecting liver function.

Common Causes Leading to Abnormal Liver Function Tests

  • Key Conditions Affecting Liver Function:

    • Hepatitis

    • Hemochromatosis

    • Non-specific liver function abnormalities

    • Various liver diseases

  • Diagnostic Complications: Ruling out other liver diseases is necessary to confirm DILI.

Mechanism of Injury and Drug Patterns

  • Patterns of Liver Injury: Different drugs cause specific types of liver injury (hepatocellular vs. cholestatic).

  • Assessment Methodology: Ratio comparison of liver enzymes used for assessing liver injury types:

    • Ratio = Change in ALT above normal / Change in ALK Phos above normal.

      • Hepatocellular Injury: High ALT and low ALK Phos changes suggest damage to hepatocytes.

      • Cholestatic Injury: Low ALT and high ALK Phos changes indicate bile duct injury.

  • Examples of Drugs:

    • Flucloxacillin and Amoxicillin/Clavulanic Acid: Commonly cause cholestatic hepatitis.

    • Note: Different drugs have characteristic profiles which can help in suspicion of DILI.

Biomarkers in Drug-Induced Liver Injury

  • Biomarker Utility: Biomarkers are used to assist in diagnosing and measuring the severity of DILI.

    • Common Enzymes: Check liver enzymes, although not very specific.

    • Specific Antibody Tests:

      • Example: Autoantibodies specific to certain drug-induced liver injuries.

    • Adducts Measurement: Detection of drug adducts (e.g., paracetamol toxic metabolites) can indicate liver injury.

    • Measuring Drug Levels: Can provide information on the potential for injury.

  • Severity Indicators:

    • Rapid onset, jaundice, impaired synthetic liver function, and hepatic encephalopathy signify severe liver injury.

  • Case Example (Paracetamol):

    • Responsible for about 50% of fulminant hepatic failure due to drug-induced injury.

    • Mechanism of Injury: Normally detoxified by phase II conjugation, but toxic metabolite causes injury when glutathione is depleted.

  • DILI Outcomes:

    • Normal liver function tests do not preclude severe liver injury; patients can have normal tests upon initial presentation.

Emerging Biomarkers and Future Directions

  • Desire for Sensitive Biomarkers: Current biomarkers may not adequately predict susceptibility or injury risk.

  • Candidate Biomarkers:

    • NaPQID Bound Proteins: Potentially a better marker for identifying those at risk of paracetamol toxicity.

    • MicroRNA-122: Non-coding RNA specific to liver injury, superior to ALT in distinguishing liver dysfunction.

      • ROC curves have shown microRNA-122 to be significantly better than ALT in accurately predicting liver injury.

Summary Points for Clinical Practice

  • Common Drug-Induced Liver Injury Causes: Keep in mind antibiotics, psychotropic drugs, herbal supplements.

  • Diagnostic Framework: Assess timing, patterns of liver injury, and rule out other liver conditions.

  • Biomarker Importance: Recognize the limitations of traditional liver tests and stay attuned to newer biomarkers that may improve outcomes.