Multi-Systems: Antimycobacterial Drugs Flashcards Preview

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Flashcards in Multi-Systems: Antimycobacterial Drugs Deck (27)
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1

Inhibits Dihydropterorate Synthetase?

PABA --| |--> --> DHF --> THF -->Nucleotides + DNA

Dapsone

Bacteriostatic

  • Dapsone is an analog of Para-aminobenzoic acid (PABA) that inhibits Dihydropteroate Synthase
  • Dapsone has the SAME Mechanism of Action as 
    • Sulfonamides
  • Human don't synthesize Folate de novo, so.... this drug is highly specific for Microorganisms

2

Clinical use of Dapsone?

  • Mycobacterium leprae (Leprosy)
    • As a component of combination therapy w/
      • Rifampin
      • Clofazimine
  • Pneumocystis jiroveci Pneumonia (PCP)
    • Prophylaxis
    • Treatment

3

What are the SEs of Dapsone?

  • Hemolysis in pts. w/ G6PD deficiency
    • or If > 200 mg/day
  • Methemoglobinemia
    • Results from the presence of iron in the ferric form instead of the usual ferrous form ( > 1% - 15%)
    • Chocolate brown color in Blood
  • GI intolerance
  • Fever
  • Rash
  • Erythema nodosum leprosum may develop resistance, Fast developing

4

Antimycobacterial that inhibits the Synthesis of
mRNA from Nucleotides + DNA?

 

Nucleotides + DNA --| |--> mRNA

 

Bactericidal or Bacteristatic?

Rifampin

Bactericidal against both Intracellular and Extracellular bacteria?

5

Antimycobacterial that inhibits
DNA-dependent RNA polymerase?

Rifampin

 

Bactericidal - readily penetrates Macrophages

6

Clinical use of Rifampin?

  • Mycobacterium tuberculosis
    • Combo therapy, NEVER USE ALONE
  • Mycobacterium leprae
    • Combo therapy
      • Dapsone
      • Clofazimine
         
  • Prophylaxis for H influenza and N meningitis (Staph)

7

What are the 4 R's of Rifampin?

  1. RNA Polymerase inhibitor
  2. Red / Orange Body fluids
  3. Rapid resistance if used alone
  4. Ramps up CYP450 system
    • Very important in HIV Patients
    • Dramatically increases the Concentration of
      Protease Inhibitors (PIs)

8

SEs of Rifampin?

  • Hepatotoxicity
    • Jaundice, Rashes, Thrombocytopenia
  • Nephritis
  • Red-Orange
    • Tears
    • Saliva
    • Urine
    • Feces

9

Inhibits the Synthesis of Mycolic acid?
(component of mycobacterial cell wall)

Bacteriostatic or Bactercidal?

Isoniazid

  • Bacteriostatic - Resting cells
  • Bactericidal - Dividing cells

10

What is the Enzyme req'd to activate Isoniazid?

Catalase-peroxidase enzyme KatG

Isoniazid is a pro-drug and must be activated

11

Clinical use of Isoniazid?

  • Mycobacterium tuberculosis
  • ONLY DRUG that can be used ALONE
    as Prophylaxis against TB
  • Given w/ Pyridoxine (Vitamin B6) to prevent Peripheral neuropahty
  • Capable of penetrating Macrophages
  • Inactivated by Acetylation

12

What are the SEs of Isoniazid (INH)?

  • INH - Injuries Neurons and Hepatocytes
    • Peripheral and Central Neuropahty
    • Hepatitis
      • Older pts. and Alcoholics
  • Hemolysis in G6PD-deficient individuals
  • Systemic Lupus Erythematous (SLE)-like Syndrome
  • Inhibits Phenytoin Metabolism
    • Anticonvulsant - Seizure

13

A prodrug that inhibits Synthase I,
Synthesis of Fatty Acid Precursors of Mycolic acid?

Pyrazinamide

MUST BE activated by Pyrazinamidase

Combo therapy - Short Term - 6 months

14

Clinical use of Pyrazinamide?

Mycobacterium Tuberculosis

15

SEs of Pyrazinamide?

  • Hepatitis
  • Hepatotoxicity
    • Not for Liver disease or Gout pts.
  • Asymptomatic Hyperuricemia
  • Arthralgias

16

Inhibits Arabinosyl Transferase?

(enzyme required for Synthesis of Arabinogalactan, a component of Cell wall)

Ethambutol

Mycobacteriostatic

17

Clinical use of Ethambutol?

  • Combo therapy to treat
  • M tuberculosis
  • M avium-intracellulare

(Bacteriostatic)

18

SEs of Ethambutol?

  • Hepatotoxicity
  • Optic Neuritis
    • Red-Green Color Blindness
    • Decreased visual acuity
  • AVOID giving to Children
  • E(ye)thambutol

19

1st Line Treatment Rx for Anti-Mycobacteria?

and

What is the mechamism for each?

"RIPE"

  • Rifampin
    • inhibits Bacterial DNA dependent RNA polymerase
      no mRNA
  • Isoniazid - activated by KatG enzyme (cat. peroxidase)
    • inhibits Syn. of Mycolid acids (cell wall
  • Pyrazinamide
    • inhibits Fatty Acid Synthase I -->
  • Ethambutol
    • inhibits Arabinosyl transferase
      --> No syn. of Arabinan (Arabinogalactan)

20

2nd Line Treatment Rx for Anti-Mycobacterial?

(usually added for multi-drig resistant Tb)

"FACES"

  • Fluoroquinolones
  • Aminosalicyclic Acid (PAS)
  • Cycloserine
  • Ethionamide
  • Streptomycin

21

Fluoroquinolones?

  • Inhibits DNA Gyrase (Topoisomerase II) and Topoisomerase IV
  • SE:
    • Stevens-Johnson Syndrome
      • Epidermis seperates from Dermis
    • Nausea, Vomiting, Headache, Seizure, Tendonitis, Photosensitivity

22

Aminosalicyclic Acid (PAS)?

  • Similar to Sulfonamides
    • Inhibition of PABA conversion by Dihydropteroate synthase
  • Bacteriostatic
  • Excreted in Urine - High Concentrations
    • Crystalluria prevented by keeping Urine Alkaline
  • GI symproms
  • Drug Fever
  • Joint pain
  • Rash
  • Granulocytopenia

23

Cycloserine?

  • Similar to Vancomycin - Irreversible inhibitor of Alanine Racemase and D-Ala-D-Ala Synthetase
  • Partial agonsit at NMDA receptors
    • Significant CNS side-effects (25%)
  • Excreted in the Urine

24

Ethionamide?

  • Inhibits the Synthesis of Mycolic acids
    • Same as Isoniazid
  • Poorly tolerated
    • Gastric Irritation
    • Metallic taste
    • Neurologic Symptoms
  • Rapid resistance Development
  • No cross reactivity w/ Isoniazid

25

Streptomycin?

  • First approved Clinically effectiv Rx for Mycobacteria
  • Does NOT enter the cells readily
    --> Bacteriostatic
  • Binds 30S subunit --> Prevents Reading of mRNA
  • ONLY FOR SEVERE CASES
  • Can cause Otototoxicity and Nephrotoxicity
    • It is an Aminoglycoside

26

Rx for the Mycobacterium Leprae (Leprosy)

(Hanson's Disease)

  • Multi-drug Theray Req'd
  • (2) Major Categories
    • Paucibacillary (PB) < 5 Lesions
      --> Rx: Dapsone and Rifampin
    • Multibacillary (MB) > 6 Lesions
      -->
      Rx: Dapsone and Rifampin and Clofazimine

27

Clofazimine?

  • Acts Very Slowly
    • Up to 50 days after the Therapy is started
  • Mechanism unknown
  • Oral Availability is Variable
  • Can accumulate in Tissues
  • Slow Secretion into the Bile
  • GI intolerance and Red Discoloration of the Skin