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Drug-induced hepatitis involves inflammation of the liver, caused by medication. Drug-induced hepatitis is similar to acute viral hepatitis but parenchymal destruction tends to be more extensive. Certain drugs can cause damage to the liver in a variety of ways:
- Acute hepatocellular damage:
- Dose-unrelated - eg, antituberculous drugs, halothane, anticonvulsants.
- Dose-related - eg, alcohol, paracetamol poisoning, amiodarone, methotrexate.
- Both dose-unrelated and dose-related liver cell damage - eg, azathioprine.
- Chronic active hepatitis - eg, isoniazid, nitrofurantoin.
- Cirrhosis - eg, alcohol, methotrexate.
- Hepatic tumours - eg, anabolic steroids, combined oral contraceptives.
- Intrahepatic cholestasis: either dose-unrelated (eg, carbimazole, erythromycin, phenothiazines) or dose-related (eg, anabolic steroids, azathioprine, oestrogens).
- Gallstones - eg, clofibrate, oestrogens.
Drug hepatoxicity can be non-idiosyncratic (predictable) or idiosyncratic (unpredictable). About 10% of cases are idiosyncratic.
- A very large number of drugs have been implicated as a potential cause of drug-induced hepatitis but with variable risk of both frequency and severity.
- Estimates vary widely but 25-50% of all cases of hepatitis and even hepatic failure may be due to adverse drug effects.
- Approximately 15% of patients with autoimmune hepatitis have drug-induced liver disease.
- The development of drug-induced liver disease is dependent on the drug as well as individual patient factors, including genetic predisposition, age, gender, pre-existing liver disease and comorbidities.
There is no specific or diagnostic clinical presentation, laboratory test or histological pattern to aid in the diagnosis of drug-induced liver disease. Clinical features vary with the pattern and severity of injury, which vary with the particular drug and the individual patient.
- Often detected by routine drug monitoring - eg, disease-modifying antirheumatic drugs.
- Symptoms and signs are similar to other causes of liver damage. Thus, identifying drug-induced hepatitis relies on the history of exposure more than any particular finding on examination or investigation.
- Clinical evidence of sensitivity to a medication may occur on the first day of its use or not until several months later, depending on the medication.
- Usually, the onset is abrupt, with chills, fever, rash, pruritus, arthralgia, headache, abdominal pain, anorexia, nausea and vomiting.
- Later, overt evidence of liver damage, such as jaundice, dark urine and an enlarged and tender liver, may develop.
- Two general pathogenic mechanisms are recognised:
- Predictable or direct: usually promptly follows an exposure to a new medication. The mechanism appears to be due to direct toxicity or a toxic metabolite - eg, paracetamol.
- Unpredictable or idiosyncratic: may be related to immune hypersensitivity; rash, fever and eosinophilia are typically present. These reactions follow exposure by a few weeks - eg, Augmentin®.
- Late-onset idiosyncratic reactions are difficult to recognise. They follow exposure by many months and usually do not display features of hypersensitivity - eg, isoniazid.
- Other causes of abnormal liver function tests.
- Other causes of hepatitis, including:
- Viral hepatitis.
- Other viral infections - eg, glandular fever, cytomegalovirus, HIV infection.
- Autoimmune hepatitis.
- Wilson's disease, haemochromatosis.
- Toxins - eg, alcoholic liver disease.
- Poisoning - eg, paracetamol poisoning, and mushroom and toadstool poisoning
- Other causes of liver failure and coagulation disorders.
Medication-induced liver injury typically presents in one of three clinical patterns:
- Hepatitis: elevated AST/ALT - eg, paracetamol poisoning, thiazolidinediones, statins.
- Cholestasis: elevated alkaline phosphatase - eg, chlorpromazine, erythromycin, oestrogens.
- Mixed picture with damage to both biliary canaliculi and hepatocytes: variable elevations in aminotransferases and alkaline phosphatase - eg Augmentin®.
- Investigations may also need to include an assessment for other causes of hepatitis and may include hepatitis viral serology, antinuclear antibodies, copper and iron levels, abdominal ultrasound, CT/MRI scan and liver biopsy.
- There is no specific treatment for drug-induced hepatitis other than discontinuing the medication that is causing the problem.
- People with acute hepatitis should avoid physical exertion, alcohol, paracetamol and any other hepatotoxic substances.
- Unfortunately, other than the use of N-acetylcysteine for paracetamol hepatotoxicity, there are no specific antidotes for drug-induced liver disease.
- Supportive care for acute liver failure and even liver transplantation may be required.
Liver failure is a possible but uncommon complication of drug-induced hepatitis. The risk of acute liver failure is dependent on the degree of abnormality of liver enzyme levels and the presence of pre-existing liver disease. The risk is higher in women.[6, 7]
- Usually symptoms subside when the causative drug has been discontinued and drug-related hepatitis subsides within days or weeks after the offending drug is stopped.
- Reactions may be severe and even fatal.
- Careful prescribing and, when recommended, monitoring of all medication in line with established guidelines.
- Always consider drugs as a cause of any patient presenting with hepatitis in order to provide early effective management.
Further reading and references
; NICE Evidence Services (UK access only)
; Drug-induced liver injury. Mayo Clin Proc. 2014 Jan89(1):95-106. doi: 10.1016/j.mayocp.2013.09.016.
; Natural history and outcomes in drug-induced autoimmune hepatitis. Hepatol Res. 2015 May 5. doi: 10.1111/hepr.12532.
; Dept of Health, July 2011
; Drug-Induced Liver Injury. Arch Pathol Lab Med. 2015 Jul139(7):876-87. doi: 10.5858/arpa.2014-0214-RA.
; Drug-induced liver injury: the dawn of biomarkers? F1000Prime Rep. 2015 Mar 37:34. doi: 10.12703/P7-34. eCollection 2015.
; Risk of Acute Liver Failure in Patients with Drug-Induced Liver Injury: Evaluation of Hy's Law and a New Prognostic Model. Clin Gastroenterol Hepatol. 2015 Jun 26. pii: S1542-3565(15)00844-7. doi: 10.1016/j.cgh.2015.06.020.
; Use of Hy's law and a new composite algorithm to predict acute liver failure in patients with drug-induced liver injury. Gastroenterology. 2014 Jul147(1):109-118.e5. doi: 10.1053/j.gastro.2014.03.050. Epub 2014 Apr 1.
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