Antitubercular Drugs

Anti-Infectives

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Examples

isoniazid (INH)rifampicin (rifampin)pyrazinamideethambutol

Prefix / Suffix: No consistent suffix

Physiology

Mycobacterium tuberculosis has a thick, waxy cell wall and slow growth, making it resistant to many antibiotics. Multi-drug therapy prevents resistance.

Mechanism of Action

Isoniazid inhibits mycolic acid (cell wall) synthesis. Rifampicin inhibits bacterial RNA polymerase. Pyrazinamide disrupts membrane transport. Ethambutol inhibits arabinosyl transferase (cell wall synthesis).

Indications

Active tuberculosis (combination therapy: RIPE)
Latent TB (isoniazid alone)

Side Effects / Adverse Effects

Isoniazid: hepatotoxicity, peripheral neuropathy (give B6/pyridoxine)
Rifampicin: hepatotoxicity, orange-red discoloration of body fluids (urine, sweat, tears)
Pyrazinamide: hepatotoxicity, hyperuricemia (gout)
Ethambutol: optic neuritis (red-green color blindness, vision changes)
GI upset (all)

Contraindications

Severe hepatic impairment
Optic neuritis (ethambutol)
Acute gout (pyrazinamide)

Nursing Considerations

Monitor liver function regularly — all 4 are hepatotoxic (LFTs at baseline and monthly)
Give pyridoxine (vitamin B6) with isoniazid (prevents peripheral neuropathy)
Warn about orange-red body fluids with rifampicin (harmless but stains contact lenses and clothing)
Baseline and periodic vision testing with ethambutol (optic neuritis)
Rifampicin reduces effectiveness of oral contraceptives — use alternative contraception
Stress importance of completing full 6–9 month course (prevents drug resistance)
Directly Observed Therapy (DOT) often used to ensure adherence
Take on an empty stomach (better absorption)

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Disclaimer: PharmPal Nurse is for education only and is not medical advice. Do not use it to diagnose, treat, prescribe, or make patient-care decisions; always verify with current drug references, your instructor, facility policy, and a licensed provider. In emergencies, call local emergency services.