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Drug Action IV > Mycobacterium (MC) - Block 3 > Flashcards

Mycobacterium (MC) - Block 3 Flashcards

1
Q

What are the sx of TB?

A

Productive cough, fatigue, night sweats

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2
Q

How do you diagnose TB?

A

Identification of organism
Chest x-ray
Tubercilin test

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3
Q

Sx of leprosy?

A

Anesthetic or paresthetic patches
Mucle atrophy
Bone resorption
Blindness

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4
Q

Diagnosis for leprosy?

A

Skin smear
ANtibody detection

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5
Q

What are the pools of mycobacterium?

A
  1. Extracellular
  2. Intracellular
  3. Necrotic pool with macrophages
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6
Q

Does prior exposure to TB protect someone from getting it a second time?

A

No

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7
Q

What is latency?

A

Capable of reactivating later and much harder to kill

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8
Q

What are drugs used for TB?

A
  1. Rifampin
  2. Isoniazid
  3. Pyrazinamide
  4. Ethambutol
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9
Q

Why is mycobacterium cell wall complex?

A

High lipid content and very complicated

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10
Q

How does FA synthesis occurs?

A

inhA (enoyl reductase) reduces acyl carrier protein (alkene) with the help of cofactor (NADH)

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11
Q

MOA of isoniazid?

A

Prodrug inhibitor of mycolic acid biosynthesis:
* acylated NADH not able to reduce alkene in fatty acid synthesis -> blocking mycolic acid synthesis

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12
Q

What is the endogenous substate mimiced by isoniazid?

A

Nicotinic acid

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13
Q

How is INH metabolized?

A

NAT (phase 2 conjugation) -> CYP450 metabolism can form an acyl radical responsible for liver necrosis

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14
Q

PK of isoniazid?

A
  1. Absorption is decreased in the presence of AI ion
  2. Well distributed (granuloma and CSH)
  3. Used alone for prophylaxis
  4. Combo for infectious condition
  5. Combined with B6 (pyridoxine) to reduce peripehral neuritis
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15
Q

What is the ansamycin ABX?

A

Rifamycin

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16
Q

MOA of ansamycin?

A

Targets bacterial DNA-directed RNA polymerase in G+

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17
Q

MOA of rifampin?

A
  1. Inhibits DNA-dependent RNA polymerase in bacterial cells by binding to b-subunit preventing transcription to RNA and translation to proteins
  2. Interacts with b-subunit of RNA polymerase when its a a2b trimer -> halting mRNA transcription -> preventing translation of polypeptides

Doesn’t stop elongation of mRNA once bindign to template strand of DNA has been intiated

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18
Q

Why is rifampin not used as a monotherapy?

A

Resistance develops quickly

19
Q

SAR of rifamycin?

A

Inhibits DNA-dependent RNA polymerase:
1. pi-pi bonding between naphthalene and aromatice amino acids of DDRP
2. Chelation to zic present in DDRP
3. H-bonding to enzyme through C21 and C23 OH

20
Q

Metabolism of rifampin?

A

Hydrolysis of Schiff base

21
Q

Describe the instability of rifampin?

A

Oxidation of parahydroxyquinone to paraquinone preventing pi-pi stacking

22
Q

ADR of rifampin?

A
  1. Excretion of red-orange color
  2. Hepatox and GI irritation
23
Q

DDI of rifampin?

A

CYP450 inducer (3A4 and 2C8/9/19) NOT D6

24
Q

Indication for rifaximin?

A

Traveler’s diarrhea, IBS-D

25
Q

What is the characterisitc of pyrazinamide?

A

Prodrug inhibitor of fatty acid symthesis -> Active against leten TB

26
Q

MOA of pyrazinamide?

A

Activated by pyrazibamidase to form pyrazinoic acid:
* Lowers pH of media
* Antimetabolite of NAD synthesis

27
Q

Indication for PZA?

A

Semidormant intracellular bacilli

28
Q

What is is the class of ethambutol?

A

Inhibitor of cell wall arabinan biosynthesis -> increases cell entry of other agents

29
Q

MOA of ethambutol?

A

Inhibits arabinosyl transferace that converts arabino to polyarbinose in AG and LAM

30
Q

ADR of ethambutol?

A

Optic neuritis with loss of visual acuity (red from green)

31
Q

What is the activity of ethionamide?

A

Activated by catalase peroxidase -> acytalates InhA or EthA leading to inhibtion of unsaturated fatty acid reduction and can produce an acyl radical

32
Q

What is PAS (para aminosalicylic acid)

A

Antimetabolte of PABA blocking folate acid synthesis

33
Q

ADR of ethionamide?

A

Hypersensitiy

34
Q

MOA of cycloserine?

A

Inhibitor of L-alanine racemase - blocks D-alanine syntheis (part of PG Mycobacterium)

35
Q

MOA of bedaquiline?

A

Breaththrough drug:
* Bonds at subunit C of ATP synthase
* Blocks the protein pump for ATP synthase

36
Q

What are the resistant mechanisms against bedaquiline?

A
  1. Mutations of ATP synthase
  2. Mutation to target: gene atpE codes of subunity
  3. Mutations in drug efflux pumps
37
Q

DDI of bedaquiline? BBW?

A

CYP3A4 inhibiton
BBW: QT prolongation from hERG channel blockage

38
Q

What is the MOA of pretomanid?

A
  1. Inhibition of cell wall mycolic acid biosynthesis in aerobic cells (replicating)
  2. Respiratory poisoning through NO release in anaerobic activity (static)
  3. Prodrug activated by deazaflavin
39
Q

Drug combos used for MAC infection?

A

Macrolides (choice): Clarithromycin, Azithromycin
Rifamycins: Refabutin
Misc: Ethambutol, Ciprofloxacin, Clofazimine

40
Q

Drug tx for leprosy?

A

Dapsone, Clofaziminem, Thalidomide

41
Q

MOA of dapsone?

A

Inhibits PABA incorporation into folic acid -> well absorbed

42
Q

MOA of clafazimine?

A

Generates ROS fro ractive carbones

43
Q

MOA and indication of thalidomide?

A

Inhibits synthesis of TNF-a

Indication: erythema nodosum leprosum

Drug Action IV (28 decks)

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