Isoniazid Dawa (Isoniazid)

Isoniazid is an antitubercular drug used within the tuberculosis disease pathway.

• Tuberculosis: eradicates actively replicating Mycobacterium tuberculosis, reducing disease progression and transmission.
• Latent TB infection: eliminates dormant bacilli to prevent future active disease in individuals with a positive infection test.

• Isoniazid inhibits the synthesis of mycolic acids, essential components of the mycobacterial cell wall, by targeting the enzyme InhA after activation by the bacterial catalase‑peroxidase KatG. This disruption compromises cell wall integrity, leading to bacterial death and clearance of Mycobacterium tuberculosis.

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

Common Side Effects

• Nausea: mild gastrointestinal upset.
• Peripheral neuropathy: tingling or numbness, often in extremities.
• Hepatotoxicity: elevated liver enzymes or mild jaundice.
• Rash: skin irritation or mild erythema.
• Fever: low‑grade temperature increase.

Serious or Rare Side Effects

• Severe hepatitis: jaundice, dark urine, abdominal pain.
• Stevens‑Johnson syndrome: severe skin blistering and mucosal involvement.
• Anaphylaxis: rapid onset of airway swelling, hypotension.
• Hemolytic anemia: especially in patients with G6PD deficiency.
• Aplastic marrow suppression: pancytopenia with fatigue and infection risk.

Before initiating therapy, clinicians should assess baseline liver function and consider risk factors for neuropathy.

• Liver monitoring: check transaminases before treatment and periodically thereafter.
• Vitamin B6 supplementation: recommended for patients at risk of neuropathy.
• Pregnancy and lactation: evaluate benefits versus potential risks; data are limited.
• Drug interactions: review concomitant medications that affect hepatic metabolism.
• Renal impairment: adjust monitoring in patients with reduced clearance.
• Store at ambient temperature: keep below 25°C in the original container, protect from moisture and direct sunlight.

Isoniazid interacts with several medicines that influence hepatic enzymes or share toxicity pathways.

Major Interactions (Avoid)

• Rifampicin: reduces isoniazid plasma levels, compromising efficacy.
• Pyrazinamide: combined hepatotoxic risk may be heightened.
• Certain antiretrovirals (e.g., efavirenz): may increase neurotoxicity.

Moderate Interactions (Monitor Closely)

• Acetylsalicylic acid: additive risk of liver injury.
• Phenytoin: may increase isoniazid metabolism, lowering exposure.
• Carbamazepine: potential for enhanced hepatotoxicity.
• Oral contraceptives: reduced effectiveness, consider alternative contraception.