Antibiotics: Antimycobacterials Flashcards
Drugs used for an Active TB infection
Isoniazid, rifampin, pyrazinamide, ethanbutol.
TB Multiple drug resistance to these drugs…
isoniazid, rifampin
TB extreme drug resistance to these drugs…
isoniazid, rifampin, fluoroquinolones, injectable second-line drugs.
TB Treatment (0-2 months)
isoniazid, rifampin, pyrazinamide, ethanbutol.
TB Treatment (2-6 months)
Isoniazid and rifampin.
Latent TB treatment
Monotherapy with either isonizaid or rifampin
Isoniazid MOA
Inhibits mycolic acid biosynthesis. Prodrug that becomes active within the bacilli. Given orally.
Isoniazid Metabolismq
metabolized through acetylation in the liver. bimodal distribution in terms of fast and slow acetylators.
Fast acetylators
eskimos, native americans and asians.
Isoniazid toxicities
Hepatitis (especially fast acetylators), peripheral neuritis (especially slow acetylators), hemolysis (G6PD), Lupus like syndrome, CNS stimulation.
Lupus like syndrome drugs
Hydralazine, isoniazid, procainamide
Rifampin MOA
inhibits DNA dependent RNA polymerase. given orally.
Rifampin spectrum
TB (active and latent), Leprosy, most gram positive cocci and some gram negative organisms.
Rifampin toxicities
hepatic enzyme inducer: VERY strong inducer of P450s. Causes drug interactions especially in HIV positive patients who are taking protease inhibitors.
Harmless orange color to body fluids
Decreases the effectiveness of birth control by inducing the metabolism of progestins.
Ethambutol MOA
Inhibits arabinosyl transferases that are involved in the synthesis or arabinogalactan in the mycobacteria cell wall. given orally. Great penetration of the CNS.
Ethambutal elimination
renal elimination. Renal dosing needed in cases of renal insufficiency.
Ethambutal toxicities
Decreased visual acuity and loss of green/red perception. Not recommended in children under 13.
Pyrazinamide MOA
Prodrug with unknown mechanism. Very active at acidic pH like the environment of the macrophage. Active against dormant organisms.
Pyrazinamide toxicities
hepatic dysfunction
Streptomycin MOA
Protein synthesis inhibitor of 30S ribosome.
Streptomycin toxicities
ototoxicity and nephrotoxicity.
streptomycin and TB
Used as a first line drug for drug resistant strains.
Rifabutin uses
Replaces rifampin in HIV-TB coinfected patients. Less potent inhibitor of P450s.
Rifabutin MOA
Same as Rifampin. Inhibits RNA polymerase.
