Isoniazid (INH)

Overview

• Antibiotic used to treat tuberculosis (TB) or prevent its reactivation.
• Can be used alone or in combination with other anti-tubercular medications.
• Mechanism of action: Inhibits the synthesis of mycolic acids, an essential fatty acid for the survival of mycobacterium.

Patient Education

Major Side Effects

• Hepatotoxicity (Liver Damage):

  • Educate patients to monitor for and report signs/symptoms such as:
    • Jaundice (yellowing of skin and sclera)
    • Vomiting
    • Dark urine
    • Fatigue
  • Advise avoidance of alcohol and other hepatotoxic medications.

• Peripheral Neuropathy:

  • Caused by interference with vitamin B6 metabolism.
  • Results in tingling and numbness in hands and feet.
  • Prophylaxis: Patients can take pyridoxine (vitamin B6 supplement).

Other Side Effects

• Effects on Blood Glucose:

  • Monitor blood glucose in patients with diabetes mellitus.
  • May impair release and action of insulin, leading to hyperglycemia.

• Vision and Dizziness:

  • Monitor for changes.

• Drug Interactions:

  • May increase risk of toxicity of anti-seizure medications like carbamazepine and phenytoin.

Administration Tips

• Antacids:

  • Avoid aluminum-containing antacids (e.g., Maalox) within one hour of taking isoniazid as they interfere with absorption.

• Timing with Food:

  • Take one hour before or two hours after a meal as food may delay absorption.