antimycobacterial drugs Flashcards by dena danji

1st line for TB

isoniazid
rifampin
rifabutin (1st line in HIV)
ethambutol
pyrazinamide

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1st line TB tx in HIV

rifabutin

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2nd line for TB

streptomycin
ethionamide
levofloxacin
amikacin

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TB tx goals

1) kill bacilli
2) prevent emergence of resistance
3) eliminate persistence bacilli to prevent relapse

needs multiple drugs and long duration of tx

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Directly Observed Treatment

recommended in noncompliant pt or in resistant strains

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Isoniazid

1st line
most potent anti-TB drug

used in combo tx

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Isoniazid MOA

pro-drug: activated by mycobacterial catalase peroxidase - KatG

targets: enoyl acyl carrier protein reductase (InhA) AND beta-ketoacyl-ACP synthase (KasA)
- similar as cell wall synthesis inhibitor

bacteriostatic and cidal

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why should isoniazid not be given alone

resistance emerges rapidly

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Isoniazid resistance

NO cross resistance with other anti-tb drugs

mutations in: deletion of KatG, acyl carrier protein mutations, inhA overexpression

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ioniazid AE

**peripheral neuritis (d/t pyridoxine deficiency) - 1st AE to be seen; easily corrected with B6

hepatotoxic

p450 inhibitor

Lupus like syndrome

if pregnant, HIGH risk of hepatitis (dec risk with B6 supplement)

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Rifamycins

rifampin, rifabutin

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rifampin

cidal, given in combo
1st line

P450 INDUCER

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rifampin MOA

block transcription by binding to beta subunit of bacterial RNA pol = inhibit RNA synth

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rifampin use

intra AND extracellular mycobacteria = m. tuberculosis AND m. kansasii

Gram - and +

can also tx MRSA (its an OPTION - not necessarily a 1st/2nd/3rd)

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rifampin resistance

mutations to rpoB

gene for B subunit of RNA pol = dec affinity of RNA pol

dec permeability

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rifampin clinical app

latent tb in INH intolerant

leprosy

prophylaxis in those w/ meningitis exposure

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rifampin AE

proteinuria

GI distress

thrombocytopenia, rashes, nephritis, liver dysfunction

orange color to body fluids

P450 inducer

(safe in pregnancy)

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isoniazid vs rifampin: P450 inducer/inhibitor

isoniazid: P450 inhibitor
rifampin: P450 inducer

If given together, inducer effect wins

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rifabutin

used in HIV pt - b/c of dec effect on CYP

substitute for rifampin if intolerable

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ethambutol

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1st line
COMBO tx

for m. tuberculosis, m. kansasii

ethambutol MOA

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inhibits arabinosyl transferases

ethambutol use

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in combo with pyrazinamide, izoniazid, rifampin

resistance happens if used alone

ethambutol AE

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*****dose dependent visual disturbances (red/green color blindness) - cannot be used in children too young to recieve sight tests –> can become permanent

confusion
hyperuricemia
peripheral neuritis

pyrazinamide

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1st line

hydrolyzed to active pyrazinoic acid

pyrazinamide use

in combo with isoniazid, rifampin, ethambutol

pyrazinamide AE/contraindications

renal/hepatic insufficiency = lower doses **nongouty polyarthralgia hyperuricemia heptaotoxicity photosensitivity only use in pregnancy when benefits outweigh risk

streptomycin

in drug resistant strains

streptomycin use

TB disease of meningitis, miliary, severe organ TB **more severe AE and inc risk of resistance = limited use

amikacin

2nd line streptomycin or multi drug resistant strains teratogenic similar AE to streptomycin

levofloxacin

if TB is resistant against 1st lines always use in combo tx teratogenic

ethionamide

no cross resistance with INH. "congener of INH" SEVERE neuro effects teratogenic

duration of isoniazid tx in latent TB

6-9 months

duration of rimfapin tx in latent TB

4 months

Empirical tx options - INITAL PHASE and duration

isoniazid + rifampin + pyrazinamide + ethambutol = 8 weeks - THEN isoniazid + rifampin = 18 weeks OR just izoniazid + rifampin + ethambutol THEN isoniazid and rifampin = 31 weeks

Leprosy combo drugs

dapsone clofazimine rifampin

dapsone

bacteriostatic | also used in PCP tx in HIV pt

dapsone MOA

inhibits folate synthesis

repository form of dapsone

acedapsone

dapsone AE

hemolysis erythema nodosum leprosum p450 inhibitor fever/hepatitis/methemoglobinemia

clofazimine

phenazine dye (can dye skin) bactericidal

clofazimine MOA

binds DNA - inhibits replication | generate oxygen radicals

clofazimine AE

red brown discoloration of skin eosinophilic enteritis (NO erythema nodosum)

WHO Leprosy tx

1-5 skin lesions: rifampin + dapsone ( 6 months) >5: rifampin + clofazimine + dapsone (12 months)

m. kansaii tx

isoniazid + rifamin + ethambutol resembles TB

m. marinum tx

2 drug combo: rifampin, ethambutol, clarithromycin, minocycline, doxycycline, sulfonamide resembles granulomatous cutaneous disease

m. avium tx

clarithromycin + ethambutol +-- rifabutin

m. chelonae tx

clarithromycin (monotherapy is adequate)

m. fortuitum tx

amikacin, cefoxitin, levofloxacin, sulfonamides, imipenem

antimycobacterial drugs Flashcards

(48 cards)