Pulmonary Tuberculosis

Question 1

What is the concept of PPD (Intradermal Skin Test)?

Answer 1

• Cellular constituents of the Mycobacterium tuberculosis induce the formation of antibodies
• The presence of these antibodies may be determined by reaction/tests

Question 2

How do you read a PPD test?

Answer 2

• ONLY the diameter of the induration is measured
• NOT the erythema
• Officially read at 48-72 hours after placement

Question 3

What is the measurement categories of PPD test?

Answer 3

• > or equal to 5 mm
• > or equal 10 mm
• > or equal to 15 mm

Question 4

When can a negative in the presence of of active TB happen in a PPD test?

Answer 4

• Overhwelming TB
• Early TB initial infection
• Protein malnutrition
• Hodgekin’s disease
• Measles
• Sarcoidosis
• AIDS or other immunosuppression
• Current viral infection
• Recent live-virus vaccine administration

Question 5

What can a positive TB test indicate?

Answer 5

• An individual has been infected in the past and continues to carry viable Mycobacteria in some tissue
• May also indicate receipt of BCG vaccine–not used in the US because not endemic in the US

Question 6

What does a positive test NOT reliably indicate?

Answer 6

• Active disease is present
• Immunity is present

Question 7

What is the preferred treatment in Latent TB?

Answer 7

Isoniazid for 9 months or INH + RPT (DOT) for 3 months

Question 8

RPT regimen

Answer 8

• Isoniazid + Rifapentine
• Not recommended in children < 2, presumed infection with resistant straint, pregnant women

Question 9

Isoniazid (INH)

Answer 9

• Abstain from alcohol (EtOH and INH to yield an increase risk for hepatoxicity)
• Peripheral neuropathy a common side effect
• Pyridoxine (Vitamin B-6) 25-50 mg/day to prevent/treat

Question 10

RIPE regimen

Answer 10

• Rifampin
• Isoniazide
• Pyrazinamide
• Ethambutol

For active TB

Question 11

RIE regimen

Answer 11

• Rifampin
• Isoniazid
• Ethambutol
• Hold pyrazinamide b/c for patients with gout, severe liver disease, pregnancy

Question 12

What are considerations
(disease state, other patient factors) for holding a antibiotic from this multi-drug regimen
against Tuberculosis?

Answer 12

• Drug interaction
• Population specific factors (HIV+, pregnancy, pediatrics)

Question 13

Rifabutin

Answer 13

• CYP450 interactions less than rifampin
• Patients on antivirals

Question 14

Rifapentene

Answer 14

Used only in once/week products

Question 15

What is the rifamycins active against?

Answer 15

• Gram-pos and gram neg cocci
• Gram pos bacilli
• Mycobacteria
• Chlamydiae

Question 16

What is the rifamycins inactive against?

Answer 16

• Gram neg enteric bacilli

Question 17

What is MOA of Rifamycin?

Answer 17

• Inhibits bacterial RNA synthesis by binding to the beta-subunit of bacterial DNA-dependent RNA polyermase (DDRP)–> prevents transcriptions by sterically blocking elongation of the nascent mRNA molecule

Question 18

What are some common side effects of the rifamycins?

Answer 18

• Rash
• Beware of the petechial rash
  * May represent Thrombocytopenia caused by Rifampin
  * Rifampin should be stopped

Question 19

What are some drug interaction with the rifamycins?

Answer 19

• Oral contraceptives
• Warfarin (increase in warfarin dose to maintain therapeutic levels)
• Azole antifungals (Voriconazole, itraconazole, fluconazole)
• Protease inhibitors (only impacts rifabutin)
• Pyrazinamide (hyperuricemia, arthralgia, and hepatotoxicity)
• Ethambutol (optic neuritis)

Question 20

Optic neuritis

Answer 20

• Manifested by visual acuity
• Unable to distinguish red from green
• Generally reversible