Anti-Mycobacterials Flashcards
How do you monitor a patient for elimination of TB?
- serial sputum specimens with smear and culture negative
- chest X-ray
Principles of TB treatment
- Multi drug therapy
- Focus on increasing adherence and dosage completion
- Adequate duration of therapy
Clinical use of Isoniazid Hal (INH)
- First line drug for active pulmonary TB
- used in combination, usually with at least two other active drugs
Resistance mechanisms to Isoniazid HCl
- Mutations in katG gene –>/ catalase peroxidase –> INH activation
- Mutation in inhA gene –>/ cell wall (mycelia acid) synthesis
Does INH spread to CNS?
yes
Clinical use of Rifampin
Only used alone in latent TB or meningitis prophylaxis because of rapid development of resistance
Does Rifampin spread to CNS?
yes
Toxicity of Rifampin
- red discoloration of body fluids
- influenza syndrome (more common with intermittent dosing)
- thrombocytopenia
Drug Interactions of Rifampin
-interactions with over 100 drugs through induction of microsomal enzymes
Clinical use of Ethambutol
- First line of TB therapy
- Helper drug that inhibits resistance to other drugs
Toxicity of Ethambutol
- Optic neuritis symptoms: blurred vision, central scotomata, red-green color vision loss, dose-related
- peripheral neuropathy
Clinical use of Pyrazinamide
- First line TB drug for first TWO MONTHS of therapy
- always used in combination
Clinical use of streptomycin
second line TB drug
Primary TB resistance
acquired at infection
Secondary TB resistance
developed during therapy
Describe resistance to two drugs
Risk of evolution of resistance to two drugs is the product of the risk of the development of each drug
What is MDR-TB?
resistance to both INH and rifampin
Consequence of rifampin resistance
eliminates short course therapy (6 months)
-requires therapy for at least 18-24 months
What is the 4 drug regimen for initial phase of TB treatment?
RIPE
- Rifampin
- INH (Isoniazid HCl)
- Pyrazinamide
- Ethambutol
What is the continuation phase of TB treatment?
RI
- Rifampin
- Isoniazid HCl
Requirements for intermittent therapy
Intermittent (2-3 times per week) therapy only with Direct Observation Therapy
6 month therapy has high success rate if:
- Adherence is high
- Sputum cultures convert by 2 months
- No major cavitary lung disease
What is extremely drug resistant TB?
Resistance to INH, rifampin, a fluoroquinolone, and 1 injectable
Fundamental strategy to TB treatment
- use at least two drugs to which patient’s TB strain is susceptible
- use only drugs that have never been used before
