Tuberculosis Meds Flashcards
Differentiate active TB from latent TB
Latent: consolidated bacteria in the lungs is encapsulated by macrophages
Active: coughing up active bacteria that escaped the macrophages’ capsule
What patients are at highest risk for developing active TB
Immunosuppressed patients (HIV)
What are the signs and symptoms of active TB?
Hemoptysis, malaise, fatigue, weight loss, night sweats, fever
T/F: Patients with latent TB can transmit TB to others.
False
What is the lifetime risk of developing active TB for both healthy individuals and in HIV patients that have latent TB?
10% lifetime risk in healthy people
10% per year in HIV patients
Define and describe MDR TB.
Multiple Drug Resistant TB: resistance to the two main drugs - isoniazid and rifampin
Name and describe the pathogen responsible for TB.
Mycobacterium TB - acid fast bacillus that is slow growing (long time to culture) and settles primarily in the apical portion of the lungs
Describe the findings of the Purified Protein Derivative (PPD) Skin Test
- 15+ mm induration: patient has latent TB
- 10 - 15 mm induration: high risk patient considered to have latent TB
- 5 - 10 mm induration: immunocompromised or known contact with active TB considered to have latent TB
Aside from the PPD skin test, what is another form of screening for TB?
IGRA blood test used to diagnose latent TB
What is the disadvantage of using the IGRA blood test in screening TB?
Cost –> more expensive than PPD skin test
What diagnostic tests are used in the identification of TB?
chest X-ray, MTB PCR, and AFB smear
How is a pregnant patient treated for TB?
No different other than avoiding streptomycin
How is meningeal TB treated differently than pulmonary TB?
Add dexamethasone (crosses BBB well) to other common TB meds
What are the key principles of treating TB?
- Kill large volume of bacteria
- Treat persisters –> TB stays in the body for a long time
- Prevent resistance
- Ensure highest level of adherence (DOT = directly observed therapy)
What are the two phases of drug therapy in TB?
Intensive: 3-4 drugs for 4 months
Continuation: 2 drugs for 2 months
List the drugs in the 4-drug regimen for treatment of TB.
R - Rifampin
I - Isoniazid
P - Pyrazinamide
E - Ethambutol
Which drug is used most commonly in the treatment of TB?
Isoniazid
Which TB treatment drug is known as the original antidepressant?
Isoniazid
Describe the mechanism of action of isoniazid relative to the treatment of TB.
Reduces formation of mycolic acid found in the cell wall of mycobacterium
State whether isoniazid is hydrophilic or lipophilic and how is it clinically relevant.
It is highly lipophilic meaning it has a high volume of distribution –> crosses BBB.
What are the significant AEs associated with isoniazid?
Hepatotoxic –> monitor LFTs and patient cannot drink alcohol
Increases excretion of vitamin B6 (pyridoxine) –> low B6 leads to peripheral neuropathy
What other drug is always given in combination with isoniazid?
Pyridoxine to supplement B6
Why is rifampin not used by itself to treat TB?
It quickly develops resistance
T/F: Rifampin has a lot of drug-drug interactions.
True: It is a potent CP-450 inducer –> it will cause other drugs to be metabolized faster
Describe the advantages and disadvantages of rifabutin in the treatment of TB.
Advantage: Less potent inducer of CP-450 –> fewer drug interactions
Disadvantage: Expensive
How is rifampin used to treat other diseases?
As adjunctive or prophylactic therapy for leprosy, staph aureus endocarditis, and neisseria meningitis
What are two significant AEs of rifampin?
Causes minor increase in LFTs –> caution when used in combination with Isoniazid
Orange discoloration of sweat, tears, sputum
Describe the mechanism of action of pyrazinamide.
Creates an acidic intracellular environment destructive to bacterium
What is the significant AE associated with pyrazinamide?
Arthralgias and increased uric acid –> caution in gout
T/F: Pyrazinamide can be used effectively to treat meningeal TB.
True: It is absorbed well into the CNS
T/F: Ethambutol is hepatotoxic.
False: It is renally eliminated
What is the significant AE associated with ethambutol?
Optic neuritis –> ophthalmology consult before starting drug
What is the first clinical indication that a patient is being affected by ethambutol’s significant AE?
Red/green color blindness
Which aminoglycoside can be used in the treatment of TB?
Streptomycin
What significant AEs are associated with streptomycin?
Nephrotoxicity and Ototoxicity
When is streptomycin used in the treatment of TB?
Rare –> mostly used in cases of resistance to first line (RIPE) agents
What drugs can be used to treat latent TB?
Isoniazid: qd for 6 - 9 months
Rifampin: qd x 4 months
