Antimycobacterial Agents (First-line TB drugs) Flashcards
Properties of Isoniazid (INH)
dose adjustment is not important for renal failure, but it is important for liver failure
MoA of Isoniazid (INH)
Isoniazid interferes with the production of Mycolic acid
A.D.M.E of Isoniazid (INH)
D: it can penetrate phagocytes and target intracellular latent TB. It also crosses the BBB
M: metabolized by the liver enzyme N-acetyltransferase. Isoniazid metabolism rate depends on the genetics
Properties of Rifampin
source: a semi-synthetic drug derived from the old anti-TB Rifamycin
MoA of Rifampin
Rifampin inhibits the RNA polymerase of mycobacteria
A.D.M.E of Rifampin
D: penetrates alveolar macrophages and target intracellular TB. no BBB penetration except in case of meningitis
M: after bile excretion, it undergoes Enterohepatic recirculation
E: excreted in the bile
Adverse Effects of Rifampin
- Discoloration of body fluids
→ including urine, sweat, and tears
→ they will have harmless orange-to-red discoloration - Thrombocytopenia
→ low plates count; patients will be more susceptible to bleeding - Cholestatic hepatitis
→ the hepatitis due to bile obstruction
MoA OF Pyrazinamide
Pyrazinamide acts as intracellular sterilizing agent along the other drugs
A.D.M.E OF Pyrazinamide
M: as the drug enters alveolar macrophages, TB will convert it into its active form Pyrazinoic acid by the enzyme Mycobacterial Pyrazinamidase
Adverse Effects of Pyrazinamide
- Hepatotoxicity
- Hyperuricemia
MoA of Ethambutol
Ethambutol inhibits the enzyme Arabinosyl transferase, the enzyme that polymerizes Arabinoglycans, the monomers of mycobacterial cell wall
Adverse Effects of Ethambutol
- Retrobulbar neuritis
→ it is the temporary loss of visual acuity and red-green color blindness
