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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
Pyrazinamide AEs
* **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
The aminoglycoside ____ is used for drug-resistant strains and is used in combinations for treatment of life-threatening tuberculous disease
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
what is the duration of treatment with **INH** for latent TB?
6-9 months
28
what is the duration of treatment with **Rifampin** with latent TB?
4 months
29
describe the 2nd line TB drugs: Amikacin Levofloxacin Ethionamide What AE do they all have in common?
* 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
describe standard regimens for **empiric treatment of pulmonary TB:**
31
describe drug resistant strains
32
describe drug resistant strains
33
describe **Leprosy/Hansen's disase**
* Caused by **M. leprae & M. lepromatis** * Primarily granulomatous disease of peripheral nerves & mucosa of upper respiratory tract * ~ 70 % cases are in India
34
what 3 drugs are used in combination for leprosy?
**Dapsone Clofazimine Rifampin**
35
describe **Dapsone**
* 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
\_\_\_\_ is the repository form of dapsone
**Acedapsone** is the repository form of dapsone
37
list the AEs for **Dapsone**
* **Hemolysis** (esp. G6PD deficiency) * **Erythema nodosum leprosum** (treated with corticosteroids or thalidomide) * **Other effects** – GI irritation, fever, hepatitis, methemoglobinemia * **CYP P450 inhibitor**
38
what drug causes **erythema nodosum leprosum**
**Dapsone**
39
describe Clofazimine
* 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
describe clofazimine AEs
* **Red-brown discoloration of skin** * GI irritation * Eosinophillic enteritis * **Erythema nodosum DOES NOT develop (drug has anti- inflammatory action)**
41
describe WHO treatment recommendations for Leprosy
42
describe atypical mycobacterium
* Present in environment * **not communicable from person to person** * Susceptible to different drugs to M.tuberculosis * Combination therapy required due to resistance
43
describe treatment options for atypical mycobacterium
44
describe treatment options for atypical mycobacterium

Pharmacology (19 decks)

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