Isoniazid Oba (Isoniazid)

• Isoniazid is an antitubercular agent used in the management of Mycobacterium tuberculosis infection.
• Tuberculosis prophylaxis: prevents progression to active disease in individuals with latent infection.
• Active pulmonary tuberculosis: contributes to bacterial eradication as part of standard combination therapy.
• Extrapulmonary tuberculosis: used together with other agents to treat disease in sites such as lymph nodes or meninges.

• Isoniazid inhibits the synthesis of mycolic acids, essential components of the mycobacterial cell wall, by targeting the enzyme InhA. This disruption compromises cell wall integrity, leading to bacterial death. The drug is most active against rapidly dividing Mycobacterium tuberculosis organisms and is typically used in combination with other antitubercular agents to prevent resistance.

Isoniazid may cause a range of adverse reactions, from mild to severe.

Common Side Effects

• Nausea or vomiting
• Loss of appetite
• Peripheral neuropathy (tingling or numbness of extremities)
• Mild skin rash or fever

Serious or Rare Side Effects

• Hepatotoxicity, including hepatitis and liver failure
• Severe allergic reactions such as anaphylaxis
• Stevens‑Johnson syndrome or toxic epidermal necrolysis
• Blood dyscrasias, including agranulocytosis and thrombocytopenia

• Before initiating therapy, several safety considerations should be addressed.
• Liver function monitoring: obtain baseline hepatic tests and repeat periodically during treatment.
• Vitamin B6 supplementation: co‑administer pyridoxine to reduce risk of peripheral neuropathy.
• Hypersensitivity avoidance: discontinue if signs of allergic reaction appear.
• Renal impairment caution: adjust monitoring in patients with reduced kidney function.
• Pregnancy and lactation: safety data are limited; use only if benefits outweigh risks.
• Store at below 25°C: keep in the original pack, protect from moisture.

Isoniazid can affect, and be affected by, several other medicines.

Major Interactions (Avoid)

• Isoniazid + rifampin/pyrazinamide: combined hepatotoxic potential increases liver injury risk.
• Isoniazid + carbamazepine: enzyme induction reduces isoniazid plasma levels.
• Isoniazid + phenytoin: increased metabolism may lower therapeutic effect.

Moderate Interactions (Monitor Closely)

• Isoniazid + alcohol: additive hepatotoxicity; monitor liver enzymes.
• Isoniazid + warfarin: may enhance anticoagulant effect; check INR regularly.
• Isoniazid + zidovudine (or other antiretrovirals): increased risk of hematologic toxicity.
• Isoniazid + oral contraceptives: may reduce contraceptive efficacy; consider alternative methods.