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Pharmacology > EXAM #4: TREATMENT OF MYCOBACTERIA > Flashcards

EXAM #4: TREATMENT OF MYCOBACTERIA Flashcards

1
Q

What kind of infection is caused by MAC in the immunocompetent?

A

Pulmonary

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2
Q

What kind of infection is caused by MAC in the immunocompromised?

A

Disseminated

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3
Q

What are the important characteristics of Mycobacterium?

A

1) Rod-shaped
2) Lipid rich cell wall with MYCOLIC ACID
3) Poor gram staining
4) ACID FAST
5) Slow growing*

Makes these bacteria challenging drug targets

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4
Q

What cells can Mycobacterium replicate in?

A

Macrophages

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5
Q

How is Mycobacterium Tuberculosis transmitted?

A

Respiratory droplets

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6
Q

What is Latent TB?

A

Infection with INACTIVE MTB

  • Asymptomatic
  • PPD positive
  • Negative CXR
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7
Q

What is Active TB?

A

Active infection with MTB

  • Symptomatic
  • Positive CXR
  • Infectious
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8
Q

What are the obstacles to MTB treatment?

A

1) Slow growing/ dormant
2) Develop resistance
3) Toxicity of drugs

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9
Q

What are the solutions to the obstacles of MTB treatment?

A

1) Multiple drug regimines
2) Drugs taken regularly
3) Drug therapy for sufficient time

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10
Q

What is direct observed therapy?

A

Therapy that is directly observed by a public health worker to ensure compliance

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11
Q

List the drugs that are approved for the treatment of TB.

A 
Rifamycin 
Streptomycin
Isoniazid 
Ethionamide 
Pyrazinamide
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12
Q

What is the most important drug for treating both latent and active TB? How much resistance is seen to this drug?

A

Isoniazid

*10% of TB strains are resistant to TB

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13
Q

How is MAC acquired?

A
  • Ingestion of contaminated food and water

- Respiratory droplets (less frequent)

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14
Q

How is the preferred treatment for active TB?

A

1) RIPE therapy for 8 weeks
2) RI only for 18 weeks

Rifampin
Isoniazid
Pyrazinamide
Ethambutol?

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15
Q

How is latent TB treated?

A

Isoniazid for 9 months

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16
Q

What is the MOA of Isoniazid (INH)?

A

Inhibits the synthesis of mycolic acid (cell wall)

*Note that is is given as a Prodrug

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17
Q

What enzyme from MTB converts INH into the active form?

A

Mycobacterial catalase peroxidase enzyme (Kat G)

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18
Q

What are the resistance mechanisms associated with INH?

A

1) Kat G mutations–can’t activate the drug

2) Increased mycolic acid synthesis

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19
Q

How is INH metabolized?

A

Acetylation

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20
Q

What is the implication of “slow acetylation” in INH therapy?

A

More toxicity seen in slow acetylators

21
Q

What are the major toxicities associated with INH?

A

1) Hepatitis
2) Peripheral neuropathy

Note that the hepatitis seen with INH is WORSE in alcoholics

22
Q

What increases the risk of peripheral neuropathy with INH aside from slow acetylation?

A

1) Malnourishment
2) Alcoholism
3) DM
4) AIDS

23
Q

What is the MOA of Rifampin?

A

Inhibition of RNA synthesis

- Binds bacterial DNA-dependent RNA polymerase

24
Q

What causes resistance to Rifampin?

A

Point mutations in bacterial DNA-dependent RNA polymerase

25
Q

What is the most common side effect associated with Rifampin?

A

Orange-red color imparted to

  • Urine
  • Feces
  • Sweat
  • Tears

….etc.

26
Q

What important drug-drug interaction is associated with Rifampin?

A

Increased elimination of many antiretrovirals in HIV

27
Q

What drug can be substituted for Rifampin in an HIV positive individual with active TB?

A

Rifabutin

28
Q

What is the MOA of Pyrazinamide?

A

Unknown but likely impedes cell wall synthesis

29
Q

How is Pyrazinamide used in clinical practice?

A

In combination with other anti-TB drugs–NOT by itself

30
Q

What is unique about Pyrazinamide in terms of its action?

A

Prefers an acidic enviornment i.e. prefers to act in acidic marophages treating intracellular MTB

31
Q

What is the mechanism of resistance to pyrazinamide?

A
  • Pyrazinamide is a prodrug that requires PYRAZINAMIDASE to become active
  • Mutations in this enzyme lead to resistance
32
Q

What adverse effect is associated with Pyrazinamide?

A

Gout/ Hyperuricemia

33
Q

What is the MOA of Ethambutol?

A

Inhibits arabinosyl transferases that are involved in mycobacterial cell wall synthesis

34
Q

Clinically what is unique about Ethambutol?

A

Also good for MAC

35
Q

What causes resistance to Ethambutol?

A

Mutations in arabinosyl transferases

36
Q

What are the adverse effects associated with Ethambutol?

A

1) Retrobulbar neuritis

2) Hyperuricemia

37
Q

What is Streptomycin?

A

Aminoglycoside antibiotic

- Interferes with bacterial protein synthesis

38
Q

What is the utility of Streptomycin in treatment of TB?

A

Currently used for the treatment of RESISTANT TB

39
Q

What are the adverse effects associated with Streptomycin?

A

Ototoxicity

Nephrotoxic

40
Q

What is a good drug to treat MAC infections (disseminated) in the immunocompromised?

A

Rifabutin

41
Q

Outline the combination therapy for MAC infection.

A

1) Macrolide
2) Rifampin or rifabutin
3) Ethambutol
4) Streptomycin

42
Q

What are the two forms of Leprosy?

A
  • Lepromatous

- Tuberculoid

43
Q

What is Lepromatous Leprosy?

A
  • Disfiguring skin lesions
  • Negative skin test
  • Large number of organisms in tissue
44
Q

What is the Tuberculoid form of Leprosy?

A
  • Milder
  • Hypopigmented plaques
  • Positive skin test
  • Few organisms
45
Q

How is Leprosy treated?

A

1) Dapsone
2) Clofazimine
3) Rifampin

These drugs are taken for YEARS

46
Q

What is the MOA of Dapsone?

A

PABA analog that inhibits folate synthesis

47
Q

What adverse effect is associated with Dapsone?

A

Non-hemolytic anemia

48
Q

What is the MOA of Clofazimine?

A

Bactericidal dye with unknown MOA

49
Q

What is the adverse effect associated with Clofazimine?

A

Red-brown to black changes in skin pigmentation

Pharmacology (64 decks)

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