16/17 - TB AntiMycobacterials Flashcards
2nd Line TB Agents
for
Drug-Resistant TB
or
Problems of Tolerance to 1st line agents
- *FLUOROQUINOLONES**
- *Levo-Moxi-Gati**
- *OXAZOLIDINONES**
- *Linezolid**
- *Diarylquinoline**
- *BEDAQUILINE**
- Nitroaromatics = Nitroimidazoles*
- *Pretomanid & Delamanid**
- still in trials for LATENT TB*
HIV & TB
Co-Infection
Symptoms & Treatment
- *IRIS**
- *Immune Reconsititution Inflammatory Syndrome**
- *Mild –> IBUPROFEN**
- *SEVERE –> CORTICOSTEROID**
high fevers
- worsening respiratory symptoms
- Inflamed lymph nodes
- new lymphadenopathy
- expanding CNS lesions,
- worsening of pulmonary parenchymal infiltrations
- new/increasing pleural effusions,
- intra-abdominal or retroperitoneal abscesses
Treatment of
M.Avium Complex
Non-Tuberculous Mycobacteria = NTM
REM-A
Rifamycin
Ethambutol
Macrolide
AMINOGLYCOSIDE
- *Nitroaromatics = Nitroimidazoles**
- *Pretomanid & Delamanid**
Uses for TB / Toxicities
Bacterial PRODRUG
require activation by M. TB
Active vs BOTH:
NON-REPLICATING TB=LATENT TB
likely due to :
multiple molecular targets due to liberation of NA
- *Rifapentine Uses**
- in comparison to RIFAMPIN*
- *LONGER HALF LIFE**
- *intermittent dosing** –> 2x a week for initial phase
ONCE A WEEK in Continuation phase
not active against Rifampin-resistant strains of M. TB
Pyrazinamide Resistance
significant HEPATOTOXICITY
↑ALT / ↑AST
Resistance via:
pncA mutations
pyrazinamidase used to activate –> pyrazinoic acid
Is this drug a Bacterial Activated PRODRUG?
What activates it?
PYRAZINAMIDE
YES
pncA
pyrazinamidase
VVV
pyrazinoic acid = active agent
Which TB Drug based on Target?
inhibits:
ARABINOSYL TRANSFERASE
affecting the synthesis of:
arabinogalactan & lipoarabinomannan in cell wall
ETHAMBUTOL
OPTIC NEURITIS
visual acuity –> red-green differentiation
TB TREATMENT
for
Intensive Phase
2 MONTHS DAILY
Kills 99% of bacteria
ISONIAZID = INH
RIFAMPIN
PYRAZINAMIDE
Ethambutol
not used if other 3 are sufficient
Treatment & Duration for:
HIV & TB Co-infection
If Recieving ART –> standard Regimen
CD4 < 50 = start within weeks
CDC > 50 = start within 8-12 weeks
- If NOT recieving ART*
- *extend continuation phase for +3 months (7 months)**
RIFABUTIN
may be substituted for rifampin –> reduce CYP450 induction
may need dosage adjustment with some PI’s & NNRTI
Oxazolidinones
Uses for TB / Concerns
LINEZOLID
targets the ribosome
Active against MDR & XDR-TB = Resistant TB
but…
BONE MARROW TOXICITY
need for long treatment
myelosuppression / various neuropathies
Fluoroquinolones
Uses for TB / Concerns
Moxifloxacin
Gatifloxacin + Levofloxicin
Used for:
DRUG-RESISTANT TB
Inhibit - DNA Gyrase
Resistance:
Mutations in gyrA subunit
AORTIC RUPTURES
- *Is this drug a Bacterial Activated PRODRUG?**
- *What activates it?**
ISONIAZID
YES
- *katG**
- *catalase peroxidase**
also:
Ethionamide = monooxygenase etA
DiarylQuinoline = Bedaquiline
Uses for TB
Targets: ATP-SYNTHASE
5 month half life –> single dose
highly potent vs:
NON-REPLICATING M.TB = LATENT TB
FDA approved for MDR-TB when no other options available
Adr:
Prolonged QT Interval + Hepatotoxicities
Ethambutol Resistance
OPTIC NEURITIS
very low resistance
OVERexpression of:
embA**+**embB**+**embC
Treatment & Duration for:
Single-drug resistant ACTIVE TB
replace resistant drug with:
FLUOROQUINOLONE
Moxi-Levo-Gati
If RIFAMPIN-Resistant –> extend to 12 months
Isoniazid Resistance
PERIPHERAL NEURITIS –> GIVE B6
HEPATOTOXICITY
65% in
- *katG** = activating enzyme
- *Missense** or Large deletions in catalase peroxidase
20% in
- *inhA** = final target
- *mutations in NADH binding site**
Diagnosis of TB
Definitive Diagnosis:
CULTURE
S/Sx:
Weight Loss / Night Sweats / Cough
HEMOPTYSIS-blood in sputum
CXR
AFB = Acid Fast Bacilli in Sputum
- *Non-Tuberculous Mycobacteria = NTM**
- *Pulmonary Infection**
TREATMENT
“REM” for 12 months of culture-negative sputum
RIFAMPIN
ETHAMBUTOL
MACROLIDE
clarithroycin or azithromycin
- may consider:*
- *moxifloxacin**
- *amikacin - streptomycin**
- *linezolid - clofazimine - trimethoprim**
Impact of NEW TB DRUGS
3 Things
↓Treatment Duration
↑Compliance –> ↓drug resistance
↓labor in DOTS
↓cost of treatment
- *Successful Treatment of MDR/XDR-TB**
- *↓**transmission of MDR-TB
- *Cure LATENT TB Infection**
- *↓**disease reservoir
Is this drug a Bacterial Activated PRODRUG?
What activates it?
ETHAMBUTOL
NOPE
inhibits arabinosyl transferase –> affects cell wall
TB TREATMENT
for
Continuation Phase
4 MONTHS DAILY
kills the small% of PERSISTANT bacteria, can come back
ISONIAZID = INH
RIFAMPIN
How does M. tb become drug-resistant
(and become progressively more so…)?
- *SPONTANEOUS MUTATIONS**
- since only confound to lungs, doesnt have a TRANSFER of RESISTANCE*
Target of Drug / Amount of Target
TB Enzymes that activate drug
↑Efflux Pump Activity
↑Cell Wall Permeability
↑Mutation Rates –> DNA REPAIR
Treatment & Duration for:
- *EXTRAPULMONARY TB**
- *&**
- *TB Meningitis**
Std Regimen + Continuation Phase = 4 - 7 months
TB Meningitis:
Std Regimen + Continuation Phase = >10months
Dexamethasone** or **Prednisolone
tapered over 6-8 weeks –> ↓mortality
Which TB Drug based on Target?
binds to:
beta-subunit rpoB of RNA polymerase
changes conformation -> prevents binding of nucleotides & inhibits initiation of transcription
RIFAMYCINS
HEPATITIS + RED URINE
INDUCTION OF CYP450 ENZYMES –> ↓Half-Life of:
steroids / anticoagulants / macrolides / imidazoles
Protease inhibitors / NNRTIs
Rifampin
- *Rifabutin**
- less p450 activation –> recommended for HIV/TB co-infection*
- *Rifapentine**
- LONG HALF LIFE –> can be dosed WEEKLY in continuation phase*
Which TB Drug based on Target?
INHIBIT:
Mycolic Acid Synthesis - C60-90 alpha alkyl
&
target inhA = long chain NAD-dependent enoyl-ACP reductase
INH covalently attaches to nicotinamide ring of NADH@ side of hydride exhange
- *ISONIAZID** = INH
- *ETHIONAMIDE = ETH**
Hepatotoxicity** & **PERIPHERAL NEURITIS –> give B6
Both are:
Bacterial-Activated Prodrugs
Isoniazid is activated by Catalase Peroxidase = katG
Ethionamide is activated by Monooxygenase = etA
Is this drug a Bacterial Activated PRODRUG?
What activates it?
RIFAMPIN
NOPE
Just binds to rpoB of RNA poymerase
- *Rifabutin Uses**
- in comparison to RIFAMPIN*
- LESS ACTIVATION OF P450*
- rifampin –> strong p450 INDUCER*
Rifamycin of choice for:
HIV/TB Co-infection when using protease inhibitors
Active vs some:
Rifampin-resistant strains of M. TB
use for:
M.AVIUM - intracellulare infection
Third Line TB Agents
approved for other disease but have no formal trials to assess efficacy in MDR/XDR TB
- *“I-C-C-T**”
- order of decreasing evidence*
IMIPENEM
Clofazimine
Clarithromycin
Thioridazine
Rifamycin Resistance
HEPATITIS + RED URINE
P450 INDUCER
Single AA substitutions in hotspot in:
rpoB
RNA polymerase subunit
Treatment & Duration for:
Latent TB Infection = LTBI
INH ALONE - 9 months
or
RMP alone - 4 months
or
INH + RifaPENTINE - 3 months
rifapentine = WEEKLY dosage
Which TB Drug based on Target?
only active in vitro at low pH <6
Requires:
Pyrazinamide** = **pncA
to generate the active agent = pyrazinoic acid
Sterilizing Activity
treatment 9mo –> 6mo
PYRAZINAMIDE
Significant HEPATOTOXICITY
↑ALT ↑AST
MOA IS UNCERTAIN
TB-SPECIFIC DRUG:
TB has deficient efflux compared to some naturally resistant mycobacteria
Strategies to Prevent Development of Drug Resistance in TB treatment
DOTS
Directly Observed Therapy Short-course
Fixed Dose Combinations:
INH + RIF + PZA
(+/- EMB)
1 drug regimen –> resistance
multiplicative resistance patterns, 2 drugs = less resistance chance
Drug Susceptibility Testing
NEVER ADD 1 DRUG TO A FAILING REGIMEN
fact that they’re failing –> ALREADY RESISTANT
