Antimicrobial agent 2 Flashcards
Mention the major classes of pn synthesis inhibitiors
1_Macrolide, lincosamides, chloramphenicol:
50 s, prevent peptide formation.
2_Aminoglycosides: 30 s
impair proofreading resulting in faulty pn
3_Tetracycline: 30 s,
block binding of tRNA.
Regarding Aminoglycosides in genneral: 1_type of action 2_spectrum and activity 3_mechanism of action 4_sutible media 5_route 6_water stable or unstable 7_post antibiotic effect? 8_drug interaction
1_bactericidal, bacterial killing-concentration dependent.
2_narrow spectrum «Aerobic G- bacilli», not effective against G-cocci, anaerobes or G+ cocci and bacilli.
3_penetrate cell wall through porin channels, enter perplasmic space, trasport across cytoplasmic mem by qctive mechanism, bind to 30 s unit, prevent formation of intiation complex, misreading of mRNA, abnormal pn inserted into cell membrane, disruption of cell membrane.
4_alkaline media> 7
5_parentral not orally
6_water unstable
7_exert long concentration dependent post antibiotic effect«residual activity after serum concentration fall below mic
8_synergistic with B. lactam antibiotics
Mention the pharmacokinetics properties of aminoglycosides and the toxicity
1_highly ionized, not absorbed or destroyed in GIT
2_cross placenta«congenital deficiency
3_not metabolized in body, excreted unchanged in urine
4_don’t cross BBB.
TOXICITY:
Nephrotoxicity
Ototoxicity
Neuromuscular blockade.
Mention the aminoglycosides
1_systemic: Streptomycin, Gentamycin, kanamycin, Amikacin, sisomicin, Netilmicin, Topramycin, paromomycin
2_Topical:
Neomycin, framycetin
Regarding Gentamycin:
1_why it’s better than Streptomycin?
2_activity against?
3_uses
1_more potent, low MIC, broader spectrum.
2_aerobic G- bacilli: enterobacter, pneumonia, H. inflenza, E. coli, klebsiella, serratia, pseudomonas
3_preventing and treatment of resp infections: pneumonia, lung abcesses
pseudomonas, klebsiella infections; burns, UTI.
Meningitis in combination with 3 generation Cephalosporins or Cephalosporins alone.
SABE; combined with pencillin, ampecillin, vancomycin.
Regarding Streptomycin:
1_why it’s less favorable?
2_uses
3_adverse effects
1_narrow spectrum, low ptency, high MIC,wide resistance
2_TB, Tularemia«drug of choice», plague, SABE
3_lowest nephrotoxicity
hypersensitivity is rare
pain at injection site
parasthesia, scotoma
contraindicated in pregnancy due to fetal ototoxicity.
Mention the Macrolides.
Erythromycin, Roxithromycin, Azithromycin, Clarithromycin, spiramycin.
Regarding Erythromycin: 1_type of action 2_spectrum of activity 3_mechanism of action 4_higly active against? 5_Resistance mechanism 6_cross resistance with what 7_suitable medium 8_limitations
1_bacteriostatic at low levels, cidal at high level.
2_narrow, mostly G+ and few G-.
3_sensetive G+ bacteria accumulate it intracellulary by active transport, bind to 50 s unit, interfere with translocation so ribosome fail to move along the mRNA.
4_S. pyogenes, S. pneumonia, N. Gonorrhea, Clostridium, C. diphethria.
5_a_cocci: pump it out.
b_Enterobacteriae: Erythromycin estrase.
c_G+ bacteria: alteration in binding site.
6_other Macrolide, clindamycin, chloramphenicol.
7_Alkaline.
8_narrow spectrum, gastric intolerance, gastric acid lability, low oral bioavailability, poor tissue penetration, short half life.
Mention the uses and advers effect of Erythromycin.
1_as alternative to pencillin
2_first choice for: Atypical pneumonia caused by mycoblasma
3_whooping cough
4_chancroid.
Adverse effects: GIT: abdominal pain, diarrhea.
hypersensitivity.
Enzyme inhibitor: rise in plasma of thyophylline, carbamazepine, valproate, warfarin.
Mention the pharmacokinetics property of Erythromycin and explain the dosage.
A-1_acid labile
2_enterc coated tablets to protect it from gastric acid but incomplete absorption
3_food delay absorption
4_its acid stable esters are better absorped
5_not pass BBB
6_exretion in bile
*prepration:
1_Erythromycin base: food lower absorption.
2_Erythromycin stearate: not affected by food, less toxic
3_Erythromycin ethyl succinate «same as above».
4_Erythromycin esteolate: relatively acid stable, food increase absorption, worst form b/c of liver toxicity.
Regarding Clarithromycin: 1_spectrum 2_why it's better than Erythromycin? 3_uses 4_combined with what to treat H. pylori?
1_same as Erythromycin but more active in; MAC, Other atypical mycobacterium, H. pylori, moroxella, legionella, mycoplasma pneumonia.
2_more acid stable, rapidly absorped, oral bioavailability 50% due to first pass metabolism.
food delay but don’t decrease absorption,
larger tissue distribution, produce active metabolites, one third of oral dose is excreted unchanged in urine
3_peptic ulcer,
Upper&lower respiratory tract infection, whooping cough, atypical pneumonia, skin infections, MAC in AIDS pts, sinusitis, otitis media
4_proton pump inhibitor, Ampecillin.
regarding Azithromycin: 1_why it's now preferred? 2_spectrum 3_pharmacokinetics 4_
1_higher efficacy, better gastric tolerance, once aday dosing,
2_expanded: more active against H. influenza, and respiratory pathogens but less against G+cocci
3improved: acid stable, rapid oral absorption, larger tissue distribution, intracellular penetration, slow release from intracellular site «long half life> 50 h», better tolerability and drug interaction profile, largely excreted unchanged in bile
4
Mention the uses of Azithromycin.
1first choice for: Legionnaires, chlamydia trachomatis (NS-urethraitis, genital infection,), chancroid and NG urethraitis
2 others: pneumonias, acute exacerbation of CB, pharyngitis, tonsillitis , otitis, prphylaxis and treatment of MAC, multidrug resistant typhoid fever, toxoplamosis
What’s the uses and dosage of spiramycin.
limit risk of transplcental transmission of toxoplasm gondii(for toxoplasmosis, and recurrent abortion in pregnant women).
dosage: 3 week courses of 3 MU, 2_3times a day, repeated after 2 weeks gap till delivery.
About chloramphenicol: 1_mechanism 2_spectrum 3_pharmacokinetics 4_side effects
1_bind to 50s unit, prevent peptide bond formation
2_wide
3_wide distribution, penetrate BBB, conjucate glucoronic acid in liver, excreted unchanged in urine.
4_rare but lethal; BMD/aplastic anemia.
Gray baby syndrome
hypersensitivity
superinfection
