Isoniazid (INH, Nydrazid)
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Class(es)
Antitubercular agent.
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Clinical use(s)
FDA approved: Active tuberculosis (HIV and non-HIV); inactive tuberculosis (HIV and non-HIV).
Off-label/clinical use: Atypical mycobacterial infection; determination of acetylation rate. -
Mechanism(s) of action
Bactericidal.
Inhibits synthesis of mycoloic acids, an essential component of the bacterial cell wall. -
Key adverse effects
Increased liver enzymes, neuropathy, neurotoxicity.
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Key drug/food interactions
Acetaminophen: ↑ risk hepatotoxicity.
Food: ↓ bioavailabilty. -
Special considerations
Avoid administration with food.
Use caution in severe renal/hepatic impairment.
BBW: Hepatitis.
Pyrazinamide(PZD)
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Class(es)
Nicotinamide analogue, antitubercular agent.
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Clinical use(s)
FDA approved: Tuberculosis.
Off-label/clinical use: -
Mechanism(s) of action
Bacteriostatic/bactericidal.
Converted to pyrazinoic acid in susceptible strains of Mycobacterium which lowers pH of environment (exact mechanism unknown). -
Key adverse effects
Hyperuricemia, N/V, Arthralgia.
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Key drug/food interactions
Rifampin: Severe hepatic impairment.
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Special considerations
Renally adjusted: CrCl < 30 ml/min.
Ethambutol (Myambutol)
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Class(es)
Antitubercular agent.
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Clinical use(s)
FDA approved: Pulmonary tuberculosis (adjunct).
Off-label/clinical use: Tuberculosis meningitis, MAC, nontuberculosis mycobacterial disease (M. kansasii). -
Mechanism(s) of action
It inhibits the synthesis of metabolites, subsequently impairing cell metabolism and cell multiplication eventually leading to cell death.
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Key adverse effects
Hepatotoxicity, anaphylaxis, optic neuritis.
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Key drug/food interactions
Aluminum-containing antacids (↓ serum concentrations of Ethambutol).
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Special considerations
Renally adjusted: CrCl < 30 ml/min.
Rifampin (Rifadin)
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Class(es)
Rifamycins, antitubercular agent.
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Clinical use(s)
FDA approved: Active or latent TB, meningococcal carriers.
Off-label/clinical use: Endocarditis (prosthetic valve), osteomylitis. -
Mechanism(s) of action
Inhibits RNA synthesis by blocking RNA transcription.
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Key adverse effects
EENT: red discoloration of tears; GI: N/C, diarrhea, flatulence; GU: red urine.
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Key drug/food interactions
Rifampin stimulates liver enzymes, which may increase the metabolism and decrease the effectiveness of many other drugs.
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Special considerations
Part of a four drug regimen for the treatment of active TB (rifampin + isoniazid + pyrazinamide + ethambutol). Has activity against organisms which create biofilms.