NCLEX Review Guide: First-Line Medications for Tuberculosis

Rifampin (R)

• Mechanism: Inhibits RNA synthesis by blocking RNA polymerase, preventing bacterial protein synthesis and reproduction.
• Major Side Effect: Orange-red discoloration of body fluids (urine, tears, saliva, sweat) - reassure patient this is harmless but permanent staining of contact lenses may occur.
• Hepatotoxicity risk requires baseline and periodic liver function monitoring (ALT, AST, bilirubin).
• Drug Interactions: Potent CYP450 inducer - reduces effectiveness of oral contraceptives, warfarin, and many other medications.

Isoniazid (I)

• Mechanism: Inhibits mycolic acid synthesis, disrupting bacterial cell wall formation in actively growing TB bacteria.
• Peripheral Neuropathy Prevention: Always administer with pyridoxine (Vitamin B6) 10-25mg daily to prevent nerve damage.
• Hepatotoxicity is most serious adverse effect - monitor liver enzymes monthly, especially in patients >35 years old.
• Contraindicated in patients with acute liver disease or history of isoniazid-induced hepatitis.

Pyrazinamide (P)

• Mechanism: Converted to pyrazinoic acid in acidic environments, effective against dormant TB bacteria in acidic lesions.
• Hyperuricemia Risk: Inhibits uric acid excretion - monitor uric acid levels and assess for gout symptoms (joint pain, especially big toe).
• Hepatotoxicity potential requires liver function monitoring, particularly when combined with other hepatotoxic anti-TB drugs.
• Most effective during first 2 months of treatment when bacterial load is highest.

Ethambutol (E)

• Mechanism: Inhibits arabinosyl transferase, preventing cell wall synthesis and acting as bacteriostatic agent.
• Optic Neuritis Warning: Can cause irreversible vision loss - baseline and monthly eye exams required, teach patient to report visual changes immediately.
• Contraindicated in children under 8 years (cannot reliably report visual symptoms) and patients with existing optic neuritis.
• Dose adjustment required in renal impairment as drug is primarily eliminated through kidneys.