35.antimycobacterial agents

Question 1

Classification of antimycobacterial drugs

Answer 1

1.synthetic
1st,2nd line

2.antimycobacteria antibiotics
1st,2nd line

Question 2

name drugs in 1st line therapy - synthetic antimycobacterial drugs

Answer 2

1.isoniazid tab.100mg
2.ethambutol -tab.250mg
3.pyrazinamid - tab.500mg

Question 3

2nd line therapy - synthetic antimycobacterial drugs

Answer 3

1.ethionamide -tab.250mg
2.para-aminosalicylic acid

Question 4

name drugs in 1st line therapy of antimycobacterial antibiotics

Answer 4

1.rifampicin - caps.150mg

Question 5

name drugs in 2nd line therapy of antimycobacterial antibiotics

Answer 5

1.rifapentine - caps.150mg
2.rifabutin - caps.150mg
3.fluoroquinolones
4.macrolides

Question 6

mechanism of action of isoniazid

Answer 6

inhibitor of bact.wall synthesis

Question 7

what are antimycobacterial drugs?

Answer 7

medications used to treat infections caused by the mycobacterium species
-tuberculosis
-leprosy

Question 8

absorption of isoniazid

Answer 8

good oral absorption

Question 9

distribution of isoniazid

Answer 9

1.high concentration in CSF
2.good intracellular distribution
3.can cross BBB and FPB

Question 10

metabolism of isoniazid

Answer 10

1. liver - acetylation

• Slow acetylators- metabolise slowly,
  efficacy higher but interferes with vitamin B6
• Fast acetylators- metabolise quickly,
  efficacy is decreased and can cause liver damage (metabolite build up is toxic to it)

2. is an Enzyme inhibitor

Question 11

excretion of isoniazid

Answer 11

urine

Question 12

MoA of isoniazid

Answer 12

1- inhibits the synthesis of mycolic acid (main component of the mycobacterial cell wall)
2- It is tuberculocidal
(works on both intra and extracellular forms)

Question 13

ADRs of isoniazid

Answer 13

1- Allergies
2- Neurotoxicity-
(in slow metabolizers – neuritis, paresthesia – can be countered with vit. B6 administration)
3- Hepatotoxicity
- Both are dose dependant and reversible
4- Tinnitus
5- Arthalgia

Question 14

MoA of pyrazinamide

Answer 14

1- Inhibits bacterial fatty acid synthesis (not fully understood)
2- Analogue of isoniazide

Question 15

ADRs of pyrazinamide

Answer 15

1.hepatotoxicity
2.hyperuricemia

Question 16

contraindications of pyrazinamide

Answer 16

1.liver impairment
2.gout - increases levels of uric acid

Question 17

absorption of ethambutol

Answer 17

oral

Question 18

distribution of ethambutol

Answer 18

good tissue distribution
can cross BBB when inflammed

Question 19

metabolism and excretion of ethambutol

Answer 19

m - none
e - urine in active form

Question 20

MoA of ethambutol

Answer 20

1- inhibits mycobacterial arabinosyltransferase
2 - the only tuberculostatic one

Question 21

contraindications of ethambutol

Answer 21

1- Liver impairment
2- Children < 13 yrs
3- Clients who cannot report visual changes

Question 22

ADRs of ethambutol

Answer 22

1- Hypersensitivity
2- Hepatotoxicity
3- Optic neuritis- most specific, dose dependant
- It is reversible but its a slow process
4- Decreased visual acuity
5- Color blindness
6- Nephrotoxicity

Question 23

Rifampicin MoA

Answer 23

1- Selectively inhibits DNA-dependent RNA-polymerase
2- Bactericidal
3- Broad spectrum
4- It is a potent enzyme inducer

Question 24

absorption of rifampicin

Answer 24

good oral

Question 25

distribution of rifampicin

Answer 25

penetrates BBB and FPB
penetrates intracellularly and extracellularly

Question 26

metabolism of rifampicin

Answer 26

liver

Question 27

excretion of rifampicin

Answer 27

bile and partially urine, sweat, saliva

Question 28

ADRs of rifampicin

Answer 28

1- Liver damage
2- Red discolouration of urine
- Harmless
3- Can stain contact lenses
- Harmless
4- Allergies
5- Nausea
6- Vomiting

Question 29

contraindications of rifampicin

Answer 29

liver impairment

Question 30

MoA of streptomycin

Answer 30

1- Inhibits bacterial protein synthesis at the ribosomal level
2- Part of aminoglycosides
3 - Only works on extracellular microorganisms
4- Resistance develops very quickly

Question 31

absorption of steptomycin

Answer 31

poor oral
only i.v and i.m

Question 32

metabolism and excretion of streptomycin

Answer 32

m - not metabolized
e - urine

Question 33

ADRs of streptomycin

Answer 33

1- Nephrotoxicity
2- Ototoxicity
3- Optic neuritis
4- Hypersensitivity

Question 34

contraindications of streptomycin

Answer 34

liver impairment