Nicozid (Isoniazid)

Isoniazid, marketed as Nicozid, is used in the antitubercular therapeutic area to combat Mycobacterium tuberculosis infection.

• Active tuberculosis: aids in rapid bacterial kill and contributes to cure when used as part of standard multidrug therapy for pulmonary and extrapulmonary disease.
• Latent tuberculosis infection: administered to individuals with a positive tuberculin skin test or interferon‑gamma release assay to lower the chance of developing active TB.
• Tuberculosis prophylaxis in close contacts: given to people who have been exposed to a contagious TB case to prevent infection from becoming active disease.

• Isoniazid exerts its antibacterial effect by inhibiting the enzyme InhA, a key component in the synthesis of mycolic acids, which are essential fatty acids of the mycobacterial cell wall. By blocking mycolic acid production, the drug compromises cell wall integrity, leading to bacterial death, particularly in actively replicating Mycobacterium tuberculosis. The pro‑drug is activated by the bacterial catalase‑peroxidase enzyme KatG, which converts it into reactive metabolites that further disrupt cellular processes.

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

Common Side Effects

• Nausea: mild stomach upset often occurring after the first doses.
• Peripheral neuropathy: tingling or numbness in hands and feet, usually reversible with supplementation.
• Rash: skin redness or itching that may resolve without intervention.
• Elevated liver enzymes: mild increase detectable in routine blood tests.

Serious or Rare Side Effects

• Hepatitis: severe liver inflammation presenting with jaundice, fatigue and abdominal pain.
• Stevens‑Johnson syndrome: rare severe skin reaction with blistering and mucosal involvement.
• Anemia: hemolytic or aplastic anemia leading to fatigue and pallor.

Before prescribing Nicozid, clinicians should consider several precautionary measures to ensure patient safety.

• Liver function monitoring: assess baseline transaminases and repeat during therapy.
• Vitamin B6 supplementation: co‑administer pyridoxine to reduce risk of peripheral neuropathy.
• Pregnancy risk assessment: evaluate benefits versus risks as isoniazid crosses the placenta.
• Alcohol consumption: advise patients to limit alcohol to lower hepatotoxicity risk.
• Store at ambient temperature: keep below 25°C in the original container, protect from moisture and light.

Isoniazid can interact with other medicines, affecting their efficacy or safety.

Major Interactions (Avoid)

• Rifampicin: concurrent use reduces isoniazid plasma levels, compromising anti‑TB effect.
• Phenytoin: isoniazid inhibits metabolism, increasing phenytoin concentrations and toxicity risk.

Moderate Interactions (Monitor Closely)

• Acetylsalicylic acid: combined use may increase risk of hepatotoxicity.
• Carbamazepine: may enhance liver enzyme induction, requiring liver function monitoring.
• Oral contraceptives: isoniazid may reduce effectiveness, advise alternative contraception.