Mycobacterium Rx (lecture) Flashcards
What is the first line Tx of TB (list of 4 drugs)?
Rifampin, Isoniazid, Pyrazinamide, and Ethambutol (RIPE)
Note: Standard care includes all four for the first two months while susceptibility is confirmed. After that isoniazid and rifampin are give for another 4 to 7 months
Ethiopian patient with 3 week history of hemoptysis, weight loss, fatigue and fever. What is the diagnostic staining of the probable infective agent?
Tuberculosis is very prevalent in Africa. Mycobacterium tuberculosis will show up as acid fast and are aerobic.
What is the MoA of isoniazid?
Inhibition of mycelia acids (cell wall).
How is isoniazid toxicity limited in the host?
It requires KatG activation, which is preferentially in Mycobacteria
What is a special consideration of Asian populations regarding isoniazid use?
They tend to be fast acetylators, leading to rapid deactivation of isoniazid (must give more to them)
What is the first line treatment for a person without a history of active TB infection, but are PPD positive for the first time?
Isoniazid
78 year old patient presents with muscle twitching and restlessness after receiving a Rx of isoniazid due to a positive PPD. What can be given to mitigate their apparent neurotoxicity? What other toxicity are they at risk of developing in response to isoniazid?
- Give B6 (pyridoxine) for the neuro involvement
- They are at increased risk of hepatotoxicity (increased risk with aging populations)
Patient with a recent PPD conversion and history of well-treated seizures comes to your office. What is a special consideration for isoniazid administration in this patient?
They may be taking PHENYTOIN (as anti epilepsy med). Isoniazid inhibits phenytoin metabolism, so you may need to lessen their phenytoin intake (30% toxicity)
What is the MoA of rifampin?
Inhibit bacterial DNA dependent RNA polymerase
Patient presents with orange-red urine two weeks after starting treatment for TB. What prescription is likely responsible for this finding and what measures should you take?
Rifampin is known to do this. There is no action required as it is NOT a sign of toxicity.
The on base child development center (day care) has an outbreak of meningitis among its infants. Culture reveals gram negative coccobacilli that are facultative anaerobes. What is the likely causative organism and what may be prescribed to the unaffected children for prophylaxis?
H. influenzae is one of the common causes of infant meningitis.
Rifampin is given prophylactically to prevent H. influenzae (is is also given for prophylaxis in some staph infections)
Patient present with a decreased ability to differentiate between red and green two weeks after starting an anti-TB regimen. What is the likely cause and etiology?
Ethambutol is known to cause optic neuritis, which may first present as loss of visual acuity and color blindness.
What is the MoA of ethambutol?
Inhibition of arabingalactan synthesis, the link between mycelia acid and peptidoglycan of the cell wall of mycobacteria
What is the MoA of pyrazinamide?
Inhibit fatty acid synthesis 1
Patient who has recently started treatment for TB is presenting with an extremely painful big toe. Arthrocentesis reveals needle-like crystals. What is the diagnosis and how should the patient be managed?
This is likely pyrazinamide-induced gout. Switch from pyrazinamide to R, I, or E and give NSAIDs for the pain.
