Isoniazid

Definition

Isoniazid is an antibiotic primarily used to treat tuberculosis (TB) by inhibiting the synthesis of mycolic acids in the bacterial cell wall. While effective against TB, it is also known for its potential to cause hepatotoxicity, which can lead to significant liver damage, especially in certain populations or under specific circumstances.

5 Must Know Facts For Your Next Test

1. Isoniazid is metabolized primarily in the liver, and its metabolism can produce toxic byproducts that may contribute to liver damage.
2. Certain individuals, including those with pre-existing liver conditions, alcohol users, and older adults, are at a higher risk for isoniazid-induced hepatotoxicity.
3. Routine monitoring of liver function tests is recommended for patients taking isoniazid to detect early signs of liver injury.
4. Symptoms of hepatotoxicity may include jaundice, dark urine, fatigue, and abdominal pain, and if these occur, isoniazid should be discontinued immediately.
5. Isoniazid can also interact with other medications that affect liver metabolism, which can increase the risk of hepatotoxicity.

Review Questions

• How does isoniazid's mechanism of action relate to its potential for causing hepatotoxicity?
  • Isoniazid works by inhibiting the synthesis of mycolic acids, which are critical for the cell wall integrity of Mycobacterium tuberculosis. This metabolic pathway occurs in the liver, where isoniazid is processed. The resulting metabolites can be toxic to liver cells, leading to hepatotoxicity. Therefore, while effectively targeting TB, its primary action in the liver contributes to potential risks associated with its use.
• Evaluate the risk factors that increase the likelihood of hepatotoxicity in patients receiving isoniazid therapy.
  • Risk factors for hepatotoxicity in patients on isoniazid include pre-existing liver disease, concurrent use of alcohol or hepatotoxic medications, and age over 35. Patients with a history of hepatic issues may have compromised liver function, making them more susceptible to drug-induced damage. Additionally, women and individuals with a slow acetylator phenotype are at greater risk due to how their bodies metabolize isoniazid.
• Synthesize a management plan for monitoring and mitigating the risks associated with hepatotoxicity when prescribing isoniazid.
  • A comprehensive management plan should include baseline liver function tests before initiating isoniazid treatment. Regular monitoring (e.g., every month) during therapy can help catch any signs of liver damage early. Educating patients about potential symptoms of hepatotoxicity such as jaundice or abdominal pain is crucial. If elevated liver enzymes or symptoms arise, discontinuing isoniazid and considering alternative treatments for TB should be discussed with healthcare professionals to ensure patient safety.

Related terms

Hepatotoxicity: The potential of a substance to cause damage to the liver, which can result in liver dysfunction and various health issues.

Tuberculosis: A highly infectious bacterial disease caused by Mycobacterium tuberculosis, primarily affecting the lungs but can also impact other parts of the body.

Mycolic Acids: Long-chain fatty acids found in the cell wall of Mycobacterium species, essential for the bacteria's survival and virulence.