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Pharmacology (3) > CH5 | Antimycobacterial Drugs > Flashcards

CH5 | Antimycobacterial Drugs Flashcards

1
Q

What shape are Mycobacteria?

A

Rod-shaped aerobic bacilli.

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2
Q

How do Mycobacteria multiply?

A

They multiply slowly.

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3
Q

What is a significant characteristic of Mycobacteria regarding resistance?

A

They have a high ability to develop resistance.

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4
Q

Where can Mycobacteria reside within the human body?

A

Within macrophages. This makes them “intracellular pathogens”.

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5
Q

What essential component is found in the cell wall of Mycobacteria?

A

Mycolic acid.

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6
Q

What type of acids make up mycolic acid?

A

Long-chain, β-hydroxylated fatty acids.

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7
Q

What is a characteristic of the mycobacterial cell wall?

A

It is lipophilic and lipid-rich.

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8
Q

What type of lesions do mycobacterial infections cause?

A

Slow-growing, granulomatous lesions, causing tissue destruction throughout the body.

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9
Q

Which part of the body is mostly affected by Mycobacterial infections?

A

The lungs.

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10
Q

What disease is primarily caused by Mycobacterium tuberculosis?

A

Tuberculosis (TB).

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11
Q

Which pathogen causes Tuberculosis (TB)?

A

Mycobacterium tuberculosis.

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12
Q

What condition occurs when a patient is infected with M. tuberculosis but shows no signs or symptoms?

A

Latent tuberculosis infection (LTBI).

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13
Q

Where do dormant mycobacteria reside in a patient with LTBI?

A

Within macrophages.

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14
Q

What are the four first-line drugs used in TB treatment?

A

Isoniazid, rifampin, pyrazinamide, and ethambutol.

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15
Q

When are second-line drugs used in TB treatment?

A

When first-line drugs are ineffective (resistant TB) or the patient cannot tolerate first-line drugs.

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16
Q

Name the classes of second-line drugs used in TB treatment.

A

Aminoglycosides, fluoroquinolones, cycloserine, and macrolides.

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17
Q

What is the role of cycloserine in TB treatment?

A

It is used as a second-line drug when first-line drugs are ineffective or intolerable.

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18
Q

What type of drug are macrolides considered in the context of TB treatment?

A

They are second-line drugs.

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19
Q

What is the reason for the long duration of TB treatment?

A

Due to the slow growth of M. tuberculosis, treatment ranges from months to years.

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20
Q

What is the duration of treatment for LTBI with isoniazid monotherapy?

A

9 months.

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21
Q

How long is the treatment duration for multidrug-resistant TB (MDR-TB)?

A

2 years.

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22
Q

What is the minimum treatment duration for TB?

A

At least 6 months.

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23
Q

What is required for the treatment of TB or MDR-TB?

A

They must be treated with multiple drugs.

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24
Q

What is the treatment approach for MDR-TB?

A

Use second-line drugs plus any effective drug from the first line.

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25
Q

What is Isoniazid considered in the treatment of tuberculosis (TB)?

A

The most active drug for the treatment of TB caused by susceptible strains.

26
Q

What type of drug is Isoniazid?

A

A prodrug that is activated by mycobacterial catalase-peroxidase (KatG).

27
Q

What enzymes does the active form of Isoniazid target?

A

Acyl carrier protein reductase (InhA) and β-ketoacyl-ACP synthase (KasA).

28
Q

What is the effect of Isoniazid on mycolic acid synthesis?

A

It inhibits mycolic acid synthesis.

29
Q

What is the mechanism of action (MOA) of Isoniazid?

A

Inhibits mycolic acid synthesis by targeting enzymes required for its synthesis.

30
Q

What is the bactericidal property of Isoniazid?

A

It is bactericidal against rapidly growing cells and intracellular organisms.

31
Q

What are the resistance mechanisms associated with Isoniazid?

A

Resistance can occur due to mutation or deletion of KatG, mutations of acyl carrier proteins, and overexpression of InhA.

32
Q

How is Isoniazid absorbed in the body?

A

Isoniazid is readily absorbed after oral administration.

33
Q

When should Isoniazid be taken for optimal absorption?

A

Isoniazid should be taken on an empty stomach.

34
Q

Where does Isoniazid diffuse in the body?

A

It diffuses into all body fluids and cells, including the cerebrospinal fluid (CSF).

35
Q

What metabolic processes does Isoniazid undergo?

A

Isoniazid undergoes n-acetylation and hydrolysis.

36
Q

How is Isoniazid excreted from the body?

A

It is excreted through glomerular filtration and secretion.

37
Q

What are the adverse effects of Isoniazid?

A
  • Hepatitis (most serious side effect).
  • Peripheral neuropathy.
  • Convulsions.
  • Rashes.
  • Fever.
  • Drug-drug interactions.
38
Q

What drug interactions does Isoniazid have?

A

It inhibits the metabolism of carbamazepine and phenytoin.

39
Q

What are the consequences of drug interactions caused by Isoniazid?

A

Ataxia and nystagmus.

40
Q

What are the examples of Rifamycins?

A

Rifampin, rifabutin, and rifapentine.

41
Q

What is the mechanism of action (MOA) of Rifampin?

A

It blocks RNA transcription by interacting with mycobacterial DNA-dependent RNA polymerase.

42
Q

What is a key characteristic of Rifampin compared to Isoniazid?

A

Rifampin has a broader spectrum than Isoniazid, targeting different bacterial infections.

43
Q

What type of bacteria does Rifampin act against?

A

It is bactericidal and effective against intracellular and extracellular mycobacteria, as well as Gram-positive and Gram-negative organisms.

44
Q

What is a major resistance mechanism for Rifampin?

A

Mutations in RNA polymerase.

45
Q

How is Rifampin absorbed after oral administration?

A

It has adequate absorption.

46
Q

How does Rifampin distribute in the body?

A

It distributes to all body fluids and organs, with CSF concentrations being 10% to 20% of blood concentrations.

47
Q

What happens to Rifampin in the liver?

A

It is taken up by the liver and undergoes enterohepatic recycling.

48
Q

How is Rifampin eliminated from the body?

A

Mainly through bile into feces, with a small percentage in urine.

49
Q

What are the common adverse effects of Rifampin?

A

Nausea, vomiting, rash, gastrointestinal upset, flu-like syndrome (fever, chills, myalgia), and rare hepatitis and death.

50
Q

What should be noted about drug interactions with Rifampin?

A

Rifampin induces cytochrome P450 enzymes, which can decrease the effectiveness of drugs such as oral contraceptives, warfarin, and certain antiretrovirals.

51
Q

What is Pyrazinamide and how is it used?

A

It is a prodrug activated to pyrazinoic acid by mycobacterial pyrazinamidase.

It is used for a short period in combination with other drugs.

52
Q

How is Pyrazinamide administered?

A

Orally.

53
Q

At what pH is Pyrazinamide active?

A

Active at low pH (5.5).

54
Q

What is the mechanism of action of pyrazinoic acid?

A

It disrupts mycobacterial cell membrane metabolism and transport functions.

55
Q

What role does Pyrazinamide play in tuberculosis treatment?

A

It acts as a sterilizing agent active against residual intracellular organisms that may cause relapse.

56
Q

What are some adverse effects of Pyrazinamide?

A

Nausea, hepatitis, hyperuricemia, rash, joint ache, and rare gout.

57
Q

How does Pyrazinamide exert its activity against mycobacteria?

A

It is taken up by macrophages and acts against mycobacteria within the acidic environment of lysosomes.

58
Q

What type of drug is Ethambutol?

A

Bacteriostatic and specific for mycobacteria.

59
Q

What is the mechanism of action of Ethambutol?

A

Inhibits arabinosyl transferases, involved in the polymerization reaction of arabinoglycan, which are required for the synthesis of the mycobacterial cell wall.

60
Q

How well does Ethambutol distribute throughout the body?

A

It distributes well, but does not achieve adequate concentrations for tuberculous meningitis.

61
Q

How is Ethambutol and its metabolites excreted?

A

Excreted in the urine.

62
Q

What are the adverse effects of Ethambutol?

A

Optic neuritis, diminished visual acuity (blurred vision), red-green color blindness, and decreased uric acid excretion.

Pharmacology (3) (15 decks)

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