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Antimicrobial's pharmacology > Antimycobacterial drugs and leprosy > Flashcards

Antimycobacterial drugs and leprosy Flashcards

1
Q

Antimycobacterial drugs

First line of treatment for mycobacteria

A

RIPE

Rifampicin, Isoniazid, Pyrazinamide, Ethambutol

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2
Q

Antimycobacterial drugs

Rifampin/rifampicin administration forms

A

PO and IV

PO readily absorbed from GI tract
IV widely distributed

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3
Q

Antimycobacterial drugs

Rifampicin/Rifampin MOA

A

Enters bacilli and binds to the ß subunit of DNA dependent RNA polymerase rpoB to form a stable drug-enzyme complex

Drug’s binding supresses chain formation in RNA synthesis

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4
Q

Antimycobacterial drugs

Rifampin/rifampicin mycobacteria

A
  • Mycobacterium tuberculosis
  • Mycobacterium leprae
  • Mycobacterium kansasii

Higher concentrations can supress Mycobacterium avium

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5
Q

Antimycobacterial drugs

Rifampin/Rifampicin therapeutic use

A

Tuberculosis and asymptomatic carriers of N. meningitidis

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6
Q

Antimycobacterial drugs

What is the necessary combination for the initial treatment of pulmonary TB?

A

Rifampin + Pyrazinamid + Isoniazid

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7
Q

Antimycobacterial drugs

Most common adverse effects of rifampin

A
  • Hepatotoxicity
  • GI distress
  • Flu like syndrome
  • Rash and hypersensitivity reactions
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8
Q

Antimycobacterial drugs

Notable harmless side effect of rifampin

A

Red orange discoloration of urine, sweat, saliva and tears

Can stain contact lenses permanently

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9
Q

Antimycobacterial drugs

Food/alcohol + rifampin

A
  • Food decreases rifampin max. plasmatic concentration
  • Alcohol should be avoided (hepatocellular toxicity)

Take with an empty stomach and full glass of water

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10
Q

Antimycobacterial drugs

Mechanism of resistance of rifampin

A
  • Alterations of rpoB
  • Efflux pumps
  • Mutations
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11
Q

Antimycobacterial drugs

Why does monoresistance to rifampin occur?

A

Intermittent dosage

Especially in HIV px or underdosage of companion drugs

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12
Q

Antimycobacterial drugs

To prevent mono or multi drug resistance, TB tx. should be prolonged…

A

9-12 months

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13
Q

Antimycobacterial drugs

Isoniazid administration

A

PO and parenteral

Pill, elixir

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14
Q

Antimycobacterial drugs

Isoniazid is a ________ activated by a _______

A
  1. Prodrug
  2. Catalase
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15
Q

Antimycobacterial drugs

The reduction of mycobacterial ferric KatG catalase-peroxidase by hydrazine and reaction with oxygen is related to _______ activation

A

Isoniazid

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16
Q

Antimycobacterial drugs

Isoniazid MOA

A

Inhibits the synthesis of mycoloic acids (essential component of the bacterial cell wall)

Inhibits InhA as a competitive inhibitor

InhA = critical role in mycoloic acid synthesis

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17
Q

Antimycobacterial drugs

Isoniazid has bactericidal activity against…

A

Actively growing Mycobacterium tb

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18
Q

Antimycobacterial drugs

Besides being first line tx. for M. tuberculosis, Isoniazid is first line for

A

M. kansasii

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19
Q

Antimycobacterial drugs

Isoniazid has moderate activity against

A

Mycobacterium bovis

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20
Q

Antimycobacterial drugs

Drug combo for Mycobacterium kansasii

A

Rifampin + ethambutol + isoniazid

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21
Q

Isoniazid

Potent inhibitor of

A

CYP2C19 and CYP3A

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22
Q

Isoniazid

Weak inducer of

A

CYP2E1

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23
Q

Isoniazid

Should not be taken with food but MUST be administered with __________

A

Vitamin B6 pyridoxine

Prevents deficiency

Take at least 1 hr before a meal or 2 after

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24
Q

Isoniazid

Consumption of histamine and tyramine containing foods with isoniazid can cause

A

Headaches, sweating, palpitations, flushing and hypotension

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25
Q

Antimycobacterial drugs

Isoniazid + antacids

A

Reduced absorption

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26
Q

Isoniazid

This leads to high-level resistance by preventing Inh activation

A

KatG mutation/deletion

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27
Q

Isoniazid

Resistance mechanisms

A
  • KatG mutation/deletion
  • InhA overexpression
  • AhpC upregulation
  • Efflux pump induction
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28
Q

Antimycobacterial drugs

Ethambutol is a _________ agent

A

Bacteriostatic

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29
Q

Ethambutol

MOA

A
  1. Diffuses into Mycobacterium cells
  2. Inhibits arabinosyltransferases III embA, embB and embC
  3. Prevents the formation of cell wall components arabinogalactan and lipoarabinomannan

Prevents cell division

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30
Q

Ethambutol

Decreased arabinogalactan causes:

A

Reduction of cell wall binding sites for mycolic acid

31
Q

Ethambutol

Reduced levels of lipoarabinomannan may interfere with

A

Mycobacterial host cells

32
Q

Ethambutol

Susceptible mycobacterium

A
  • M. gordonae
  • M. marinum
  • M. scrofulaceum
  • M. szulgai
33
Q

Antimycobacterial drugs

Only mycobacterial drug that can treat gram positives, gram negatives and mycobacteria

A

Rifampin/rifampicin

34
Q

Ethambutol

Therapeutic uses

A
  • TB
  • Disseminated Mycobacterium avium complex
  • M. kansasii infection
35
Q

Ethambutol

Most serious side effect

A

Optic neuritis

Decreased visual acuity and loss of red-green discrimination

36
Q

Ethambutol

Common and possible side effects

A
  • Diminished visual acuity
  • Rash
  • Drug fever
  • Pruritus
  • GI
  • General discomfort
  • Confusion, disorientation, hallucinations
  • Joint pain
37
Q

Ethambutol

Side effect in 50% of the patients taking ethambutol

A

Hyperuricemia

Due to reduced renal uric acid excretion

38
Q

Antimycobacterial drugs

Food and drugs + ethambutol

A
  • Take separate from antacids
  • Do not take aluminum hydroxide (at least 4 h before)
  • Take with food (reduces GI discomfort)
39
Q

Ethambutol

Resistance

A
  • Mutations in the emB gene that encodes arabinosyltransferases
  • Enhanced efflux pumps

Mutations are necessary but insufficient to induce resistance

40
Q

Antimycobacterial drugs

Pyrazinamide administration

41
Q

Antimycobacterial drugs

Pyrazinamide is ____ and only active in ________ conditions

A
  • Bactericidal
  • Acidic
42
Q

Pyrazinamide

MOA

A
  1. Enters M. tubercuosis cells
  2. Turns into pyrazinoic acid (POA-) by pyrazinamidase (pncA gene)
  3. POA- inhibits PanD (coenzyme A synthesis)
  4. Protein degradation
43
Q

Pyrazinamide

What is the role of ribosomal protein S1 (RpSA) in pyrazinamide use?

A

Target
* Disrupts protein recycling
* Causes toxic buildup

Helps kill the bacteria

44
Q

Pyrazinamide therapeutic use

A

M. tuberculosis

45
Q

Adding pyrazinamide to isoniazid and rifampin containing regimens helps to

A

Shorten treatment duration from 9-12 months to 6 months

46
Q

Pyrazinamide adverse effects

A
  • Blood clotting
  • Vascular integrity
  • Hyperuricemia
  • Hepatotoxicity
47
Q

Pyrazinamide

Food and drug interactions

A
  • Absorption is unaffected by food
  • Acetaminophen may decrease pyrazinamide excretion rate
48
Q

Pyrazinamide

Contraindicated medical conditions

A
  • Hepatic faillure
  • Acute gout
49
Q

Pyrazinamide

Pregnancy and breastfeeding

A

Only if benefits outweight the risks

50
Q

Pyrazinamide

Resistance mechanisms

A
  • Mutations in pncA, rpsA, panD
  • Efflux pumps
51
Q

Antimycobacterial drugs

Can cause drug-induced lyme disease

A

Isoniazide

52
Q

Antimycobacterial drugs

B6 defficiency, seizures, neuropathy and anemia can be caused by the use of

53
Q

Leprosy drugs

Group of leprosy drugs

54
Q

Name the sulfone used for leprosy

55
Q

Animycobacterial drugs

Dapsone administration and absorption

A
  • Complete absorption after PO
  • Tends to be retained 3w in skin and muscle (and especially in the liver and the kidney)
56
Q

Antimycobacterial drugs

Dapsone MOA

A
  • Structural analogue of PABA
  • Competitive inhibitor of DHT sin the folate pathway
57
Q

Antimycobacterial drugs

Dapsone anti-inflammatory effects

A

Occur via inhibition of tissue damage by neutrophils

58
Q

Antimycobacterials

What moo’ is dapsone bacteriostatic against?

59
Q

Antimycobacterial drugs

Dapsone acts against these parasites:

A
  • Plasmodium falciparum
  • Toxoplasma gondii tachyzoites
60
Q

Antimycobacterial drugs

Dapsone acts against this fungus

A

Pneumocystis jirovecii

61
Q

Antimycobacterial drugs

T/F Dapsone is only an antibacterial agent

A

False

Antibacterial, antiprotozoal and antifungal effects

63
Q

Antimycobacterial drugs

Dapsone + rifampin

A

Leprosy tx.

64
Q

Antimycobacterial drugs

T. gondii prophylaxis

65
Q

Antimycobacterial drugs

Dapsone has anti-inflammatory effects in…

A
  • Pemphigoid
  • Dermatitis herpetiformis
  • Immunoglobulin A bullous disease
  • Relapsing chondritis
  • Ulcers caused by the brown spider
66
Q

Antimycobacterial drugs

Sulfone used for the treatment of acne vulgaris, Hansen’s disease and dermatitis herpetiformis

67
Q

Antimycobacterial drugs

Severe metahemoglobinemia may ocurr in patients with NADH-dependent metahemoglobin reductase deficiency taking ___________

68
Q

Antimycobacterial drugs

Dapsone adverse effects

A
  • Hemolysis
  • Metahemoglobinemia
  • Peripheral neuropathy
  • Insomnia
  • Psychosis
  • Drug fever
  • Infectious mononucleosis-like syndrome (potentially fatal)
69
Q

Antimycobacterial drugs

T/F: Hematuria can be seen in certain cases of dapsone use

70
Q

Antimycobacterial drugs

Food and dapsone

A

Take with or without food

Absorption is unaffected by food

71
Q

Antimycobacterial drugs

Primary mechanism of resistance of dapsone

A

Mutations in genes that encode dihydropteroate synthase

72
Q

Major drug interactions of rifampin

A

Strong CYP450 inducer (decreases effectiveness of oral contraceptives, warfarin, protease inhibitors, and many other drugs)

HIV cases - prefer rifabutine

73
Q

Who should use rifampin with caution?

A

🚨 Patients with liver disease or alcoholism (increased risk of hepatotoxicity)
🚨 Patients on other hepatotoxic drugs (e.g., isoniazid, pyrazinamide)

Antimicrobial's pharmacology (7 decks)

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