Compare the number of organisms present in cavitary pulmonary TB and TB infection without the disease. Explain how this affects treatment.
- - Cavitary pulmonary TB: 10^7 - 10^8 organisms
- - TB infection w/o disease: <10^5
Because mutations occur in ~1/10^6 to 1/10^8 organisms, multiple drugs must be used to treat cavitary pulmonary TB in order to prevent emergence of resistant strains. TB infection w/o the disease, however, has few enough organisms that mutation is unlikely and can, therefore, be treated with a single drug.
When is an induration > or = to 5mm indicative of TB infection?
- For persons with:
- - HIV
- - immunosuppressive therapy
- - close contact with infectious cases
- - fibrotic lesions on CXR
When is an induration > or = to 10mm indicative of TB infection?
- When the person is:
- - an immigrant w/i the last 5 years
- - an IV drug user
- - a hospital employee
What size induration is indicative of TB infection in persons with no defined risk?
PPD induration > or = to 15mm.
What is the preferred treatment for latent TB?
INH (isoniazid) daily for 9 months.
What factors increase a person's risk of developing TB?
- - smoking tobacco
- - vitamin D deficiency
What factors should be considered when taking INH?
Food decreases absorption and INH should be given on an empty stomach.
Toxicities of INH.
- - Hepatitis: incidence increases with age; liver enzymes should be monitored in persons >35 y/o.
- - Peripheral neuropathy: caused by interferance with pyridoxine (B6) metabolism; prevent/treat with pyridoxine daily
- - Diarrhea: secondary to sorbitol in liquid form of INH
Drug interactions of INH.
Phenytoin: will increase concentration of both drugs in system
Rifampin, Rifabutin, Rifapentine
Used to treat TB (not usually first line drug).
Administration considerations for Rifampin, Rifabutin, Rifapentine.
- - Turns body fluids orange; excreted in urine, tears, and sweat.
- - Give on empty stomach.
- - Rifampin/Rifabutin are 1x/day; Rifapentine is 1x/week
Toxicities of Rifampin, Rifabutin, and Rifapentine.
- - Common: GI (nausea, vomittine)
- - Rare: hepatitis
- - Orange colored body fluids
Drug interactions with Rifampin, Rifabutin, Rifapentine.
- Rifampin, Rifabutin, and Rifapentine are potent inducers of hepatic enzymes and therefore reduce blood levels of:
- - methodone (leading to withdrawl)
- - warfarin (leading to decreased INR)
- - oral contraceptives (leading to decreased effectiveness)
Toxicities of Pyrazinamide.
- Hepatitis (monitor liver enzymes)
- GI (nausea, vomitting)
- Hyperuricemia (decreases uric acid secretion)
Toxicities of Ethambutol.
- Optic neuritis (blurred vision, red/green blindness, restricted visual fields); dose related; do regular eye exams
- TB treatment.
- Includes: levoflozacin and moxifloxacin
Combination TB drugs.
- Rifamate: INH and Rifampin
- Rifater: INH, Rifampin, and Pyrazinamide