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Pharmacology > Antimycobacterials > Flashcards

Antimycobacterials Flashcards

1
Q

describe the image below

A
  • Mycobacterium tuberculosis
  • Small, aerobic, non-motile, bacillus
  • Can lead to serious infections of the lungs, genitourinary tract, skeleton & meninges
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2
Q

list 1st line TB drugs

A

“RIPE”

  • Rifampin
    • Rifabutin (1st line in HIV pts)
  • Isoniazid
  • Pyrazinamide
  • Ethambutol
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3
Q

list 2nd line TB drugs

A

“SALE”

  • Streptomycin
  • Amikacin
  • Levofloxacin
  • Ethionamide
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4
Q

describe people who are at high risk of TB/need prophylaxis

A
  • Persons who have been recently infected with TB bacteria
  • Persons with medical conditions that weaken the immune system
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5
Q

describe isoniazid

A
  • Synthetic analog of pyridoxine
  • First-line agent
  • Most potent antitubercular drug
  • Part of COMBINATION THERAPY for active infection
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6
Q

___ is the sole drug in treatment of latent infection

A

Isoniazid is the sole drug in treatment of latent infection

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7
Q

Isoniazid is converted to its active form via ___ and targets enzymes required in _____ synthesis such as:

A

Isoniazid is converted to its active form via catalase- peroxidase - KatG and targets required in mycolic acid synthesis such as:

  • enoyl acyl carrier protein reductase (InhA)
  • b-ketoacyl-ACP synthase (KasA)
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8
Q

what happens if INH is used alone?

A

resistant organisms rapidly emerge

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9
Q

how does TB create resistance against INH?

A
  • Chromosomal mutations resulting in:
    • mutation of deletion of KatG
    • mutations of acyl carrier proteins
    • overexpression of inhA
  • Cross-resistance between other anti-tuberculosis drugs DOES NOT OCCUR
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10
Q

describe adverse effects of INH

A
  • Peripheral neuritis: corrected by pyridoxine supplementation
  • Hepatotoxicity: clinical hepatitis & idiosyncratic
  • CYP P450 inhibitor
  • Lupus-like syndrome: rare
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11
Q

is INH safe in pregnany?

A

yes, use pyridoxine supplementation

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12
Q

describe Rifamycins

A
  • Rifampin & rifabutin
  • 1st drugs for treatment of all susceptible forms of TB
  • Part of COMBINATION THERAPY for active infections
  • Sole drug in treatment of latent infection (2nd line)
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13
Q

Rifampin is usually given in ____

A

Rifampin is usually given in combination

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14
Q

what is Rifampins MOA?

A

Blocks transcription: binds to B subunit of bacterial DNA-dependent RNA polymerase → inhibition of RNA synthesis

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15
Q

describe resistance to Rifampin

A
  • Point mutations in rpoB (gene for B subunit of RNA polymerase) → decreased affinity of bacterial DNA-dependent RNA polymerase for drug
  • Decreased permeability
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16
Q

what are the clinical applications of Rifampin?

A
  • Active TB infections
  • Latent TB in isoniazid intolerant patients
  • Leprosy (delays resistance to dapsone)
  • Prophylaxis for:
    • individuals exposed to meningitis
    • contacts of children with H.influenzae type B
  • MRSA (with vancomycin)
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17
Q

Rifampin is a strong ____ inducer

A

Rifampin is a strong CYP450 inducer

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18
Q

list the AEs with Rifampin

A
  • Light chain proteinuria
  • GI distress
  • Occasional effects: thrombocytopenia, rashes, nephritis, liver dysfunction
  • Imparts harmless orange/red color to bodily fluids
  • Strongly induces CYP P450
  • SAFE IN PREGNANCY
19
Q

describe what caused this

A

Rifampin!

AE: yellow/orange bodily fluids

20
Q

___ is the referred drug for use in HIV patients (due to less induction of CYP enzymes)

A

Rifabutin is the referred drug for use in HIV patients (due to less induction of CYP enzymes)

Rifampin substitute to those that are intolerant

21
Q

describe Ethambutol

A
  • 1st line for all susceptible forms of TB
  • Specific for most strains of M.tuberculosis & M.kansasii
  • Used in combination with pyrazinamide, izoniazid & rifampin
  • Resistance occurs rapidly if used alone
    • mutations in emb gene
22
Q

Ethambutol inhibits ____ leading to decreased carbohydrate polymerization of cell wall

A

Ethambutol inhibits arabinosyltransferase leading to decreased carbohydrate polymerization of cell wall

23
Q

Ethambutol AEs

A
  • Dose-dependent visual disturbances (eg, red/green color blindness) – cannot be used in children too young to receive sight tests
  • Headache, confusion, hyperuricemia, peripheral neuritis (rare)
  • Safe in pregnancy
24
Q

describe Pyrazinamide

A
  • First-line agent
  • Used in combination with isoniazid, rifampin & ethambutol
  • Must be enzymatically hydrolysed to active pyrazinoic acid. Mechanism of action remains unclear
  • Resistant strains lack pyrazinamidase or have increased efflux of drug
25
Q

Pyrazinamide AEs

A
  • Nongouty polyarthralgia (~ 40%)
  • Acute gouty arthritis (rare unless predisposed)
  • Hyperuricemia
  • Hepatotoxicity, myalgia, GI irritation, porphyria, rash, photosensitivity
  • Recommended for use in pregnancy when benefits outweigh risks
26
Q

The aminoglycoside ____ is used for drug-resistant strains and is used in combinations for treatment of life-threatening tuberculous disease

A

The aminoglycoside streptomycin is used for drug-resistant strains

  • Life-threatening tuberculous disease:
    • meningitis
    • miliary dissemination
    • severe organ tuberculosis
  • Increasing frequency of resistance to streptomycin limits use of drug
27
Q

what is the duration of treatment with INH for latent TB?

A

6-9 months

28
Q

what is the duration of treatment with Rifampin with latent TB?

A

4 months

29
Q

describe the 2nd line TB drugs:

Amikacin

Levofloxacin

Ethionamide

What AE do they all have in common?

A
  • Amikacin
    • Used for streptomycin- or multi-drug-resistant strains. Similar AE to streptomycin
  • Levofloxacin
    • Recommended for use against first-line drug- resistant strains. Always use in combination.
  • Ethionamide
    • Congener of INH (no cross-resistance). Severe GI irritation, adverse neurologic effects, hepatotoxicity & endocrine effects.
  • Common AE: Teratogenic
30
Q

describe standard regimens for empiric treatment of pulmonary TB:

A
31
Q

describe drug resistant strains

A
32
Q

describe drug resistant strains

A
33
Q

describe Leprosy/Hansen’s disase

A
  • Caused by M. leprae & M. lepromatis
  • Primarily granulomatous disease of peripheral nerves & mucosa of upper respiratory tract
  • ~ 70 % cases are in India
34
Q

what 3 drugs are used in combination for leprosy?

A

Dapsone
Clofazimine
Rifampin

35
Q

describe Dapsone

A
  • Structurally related to sulfonamides
  • Bacteriostatic
  • Inhibits folate synthesis (via dihydropteroate synthetase inhibition)
  • Also used in treatment of pneumonia (P.jiroveci) in HIV +ve patients
36
Q

____ is the repository form of dapsone

A

Acedapsone is the repository form of dapsone

37
Q

list the AEs for Dapsone

A
  • Hemolysis (esp. G6PD deficiency)
  • Erythema nodosum leprosum (treated with corticosteroids or thalidomide)
  • Other effects – GI irritation, fever, hepatitis, methemoglobinemia
  • CYP P450 inhibitor
38
Q

what drug causes erythema nodosum leprosum

A

Dapsone

39
Q

describe Clofazimine

A
  • Phenazine dye
  • Binds to DNA & inhibits replication
  • Redox properties may generate cytotoxic oxygen radicals
  • Bactericidal to M.leprae (some activity against M. avium- intracellulare complex)
40
Q

describe clofazimine AEs

A
  • Red-brown discoloration of skin
  • GI irritation
  • Eosinophillic enteritis
  • Erythema nodosum DOES NOT develop (drug has anti- inflammatory action)
41
Q

describe WHO treatment recommendations for Leprosy

A
42
Q

describe atypical mycobacterium

A
  • Present in environment
  • not communicable from person to person
  • Susceptible to different drugs to M.tuberculosis
  • Combination therapy required due to resistance
43
Q

describe treatment options for atypical mycobacterium

A
44
Q

describe treatment options for atypical mycobacterium

A

Pharmacology (19 decks)

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