Isoniazid

Administration

• Type: Anti-TB
• Dosage Forms:
• Routes of Administration: PO, IM
• Common Trade Names: INH

Adult Dosing

• Typically 5 mg/kg (or 300mg) daily

Pediatric Dosing

• ≤40 kg: 10-15 mg/kg daily, maximum 300mg/dose
• >40kg: 5 mg/kg daily max 300mg/dose

Special Populations

Pregnancy Rating

• Category A

Lactation risk

• Considered compatible with breast feeding

Renal Dosing

• No adjustment

Hepatic Dosing

• No official adjustment necessary per manufacturer's labeling but use with caution in patient's with preexisting liver disease

Contraindications

• Allergy/hypersensitivity to class/drug
• Prior history of hepatic injury or severe adverse reaction to isoniazid
• Acute liver disease

Adverse Reactions

Common

• Increased serum transaminases

Pharmacology

• Half-life: Fast acetylators: 30 to 100 minutes, slow acetylators: 2 to 5 hours
• Metabolism: Hepatic
• Excretion: Mostly urine

Mechanism of Action

• Inhibits synthesis of mycoloic acids (essential bacterial cell wall component)

See Also

• Isoniazid toxicity

References

• Nahid P, Dorman SE, Alipanah N, et al. Official American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America Clinical Practice Guidelines: Treatment of Drug-Susceptible Tuberculosis. Clin Infect Dis. 2016;63(7):e147-e195.
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