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36 Cards in this Set
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How do our ribosomes differ from bacterial ribosomes? What are the ribosomal agents (block protein synthesis)?
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Us: 40S + 60S = 80S
Bacteria: 30S + 50S = 70S SAT (bind to 30S) C MLS L (bind to 50S) SAT = spectinomycin, aminoglycosides, tetracyclines C = chloramphenicol MLS = macrolides, lincosamides, streptogramins L = linezolid |
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What are the four major ways bacteria develop resistance to these antimicrobials?
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1) Change in receptor structure
2) Change in drug permeation and transport 3) Change in metabolic pathways 4) Drug-inactivating enzymes |
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What is the MOA of spectinomycin and what is it used for?
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Inhibit initiation complex, bacteriostatic
IM/IV for GONORRHEA, second-line for beta-lactam allergy |
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What are the aminoglycosides? What is special about their antibiotic effect?
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Streptomycin, Gentamicin, Tobramicin, Neomycin, Amikacin, Netilmicin
bacteriCIDAL concentration-dependent killing, post-antibiotic effect - give single, large dose |
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How are aminoglycosides administered? When do you have to change the dosage? What special conditions do they require? How is their distribution?
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IV/IM - polar, not absorbed well
MAJOR dosage change in renal failure (bc renal clearance) Oxygen-dependent transport (activity against aerobic bacteria) Better activity at basic pH (bc polar) Wide distrib except CNS, sputum, bile, prostate |
Exception: neomycin - topical or oral
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What is the primary MOR to aminoglycosides?
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Group transferases (drug-inactivating enzymes)
Netilmicin less susceptible |
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What is the spectrum of the aminoglycosides?
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Aerobic gram(-) bacteria, incl. Pseudomonas
NOT gram(+) and anaerobes |
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What are gentamicin, tobramycin, and amikacin used for?
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Serious inf of aerobic gram(-) rods, until organism is known
Use with beta-lactams for synergy and gram(+) coverage |
Amikacin: less susceptible to resistance
Coverage includes E coli, Enterobacter, Klebsiella, Proteus, Providencia, Pseudomonas, Serratia, H flu, Moraxella catarrhalis, Shigella |
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What is the use of streptomycin?
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MDR (multi-drug resistant) TB, plague, tularemia (2nd line drug)
2nd line bc of OTOTOXICITY (vestibular damage) |
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What is the use of neomycin and kanamycin? Why is their use restricted?
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Oral and Topical, limited bc toxic!!
Oral: eliminate gut flora before GI surgery or in liver failure Toxic! Ototoxicity (cochlear damage) |
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What is the use of netilmicin?
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Serious infections caused by organisms resistant to other aminoglycosides (less susceptible to group transferases)
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What are the major toxicities of aminoglycosides?
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OTOTOXICITY (auditory/vestibular damage, CN VIII) -- fetal exposure, CI in pregnancy unless benefits outweigh risks
NEPHROTOXICITY: monitor dose! esp in elderly or pts on amphotericin B, cephalosporins, vancomycin Neuromuscular blockage rare (tx with calcium, neostigmine) Allergic skin rxns |
(auditory): more likely with amikacin, kanamycin
(vestibular): gentamicin, tobramycin (nephrotox): gentamicin, tobramycin (skin): neomycin |
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What are the tetracyclines? What is their MOA?
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Tetracycline, Doxycycline, Minocycline, Tigecycline, Demeclocycline
Bind to 30s, block binding of aminoacyl-tRNA to mRNA-ribosome complex, bacteriostatic |
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What is the main MOR to tetracyclines?
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Efflux pump
NOT to tigecycline |
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What impairs the absorption of tetracyclines? How are the tetracyclines metabolized?
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Foods, calcium, iron, aluminum impair good absorption (except doxycycline, feces)
Excreted by kidney (except doxycycline) |
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What are the toxicities of tetracyclines? Where are they CI?
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Pretty safe
GI (ulcers - doxycycline) Bone abnormalities/dental enamel deposits to age 8 -- CI in PREGNANCY and CHILDREN Hepatotoxicity Renal tox -- CI in RENAL FAILURE Photosensitivity (doxycycline, demeclocycline) Vertigo (doxycycline, minocycline) |
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What is the spectrum of the tetracyclines? What are their uses?
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Broad! gram(+), gram(-), staph/strep, enterics, most anaerobes
Primary uses: Adult pneumonias (Mycoplasma pneumonia, Chlamydia pneumonia), STDs (Chlamydia), Rickettsia (rocky mountain spotted fever), Lyme disease, Vibrio species Secondary: alternate tx for syphilis, rtis, prophylaxis for bronchitis, leptospirosis, acne |
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What are the other specific uses for tetracycline, doxycycline, and demeclocycline?
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tetracycline: ulcers by H pylori
doxycyline: Lyme disease, prevention of malaria, tx of amebiasis demeclocycline: ADH-secreting tumors |
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What are the special features of tigecycline? What is its use?
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More broad spectrum, less resistance: includes MRSA/VRE, beta-lactam resistant gram(-), anaerobes, atypical (mycoplasma, mycobacteria)
IV only, long half life, liver clearance (only CI pregnancy, children, or if need cidal action) Use: complicated hospital infections |
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What is the MOA of chloramphenicol? What is the MOR?
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Bind peptidyl transferase to inhibit transpeptidation of tRNA, bacteriostatic
Acetyltransferases inactivate drug (like aminoglycosides) |
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What is the penetration and mode of administration of chloramphenicol? How is the drug inactivated?
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CNS, crosses placenta; Oral
Inactivated by hepatic glucuronosyltransferase; liver enzyme inhibitor |
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What is the spectrum of chloramphenicol and what are its uses?
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Broad: gram(+/-), anaerobes
Use: Topical eye inf, CNS (meningitis, brain abscesses) -- LIMITED bc TOXIC systemic effects |
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What are the toxicities of chloramphenicol?
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LETHAL aplastic anemia (toxic to mitochondrial ribosomes)
GREY BABY syndrome: infants lack hepatic glucuronosyltransferase -- cyanosis, CV collapse, flaccidity GI, drug interactions (enzyme inhibitor), adjust with kidney failure |
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What is the MOA of macrolides, lincosamides, and streptogramins? What is the MOR to MLS?
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Bind 50S ribosome, prevent translocation (streptogramins are bacteriCIDAL)
MOR: receptor methylation (drugs don't recognize receptor) |
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What are the macrolides? What are their common toxicities?
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Erythromycin, Clarithromycin, Azithromycin, (Telithromycin - similar)
GI upset Cholestatic hepatitis Arrhythmias (long QT) |
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How is erythromycin administered and what are its kinetics? What are its uses? What are its toxicities?
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Oral, IV, wide distribution
Similar spectrum to penicillin G, (gram+ staph/strep, anaerobes) use for penicillin allergies DOC for atypicals (Legionnaires, Mycoplasma, Chlamydia, Corynebacteria, Bordetella, Camplybacter) Use for GASTROPARESIS bc GI AE so severe! Also, allergies, phlebitis CYP450 inhibitor |
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How is clarithromycin administered and distributed? What are its uses? When is it CI?
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Oral, concentrates in RESP tissue, similar spectrum to E-mycin
Use: community RTIs, also atypical Mycrobacteria CI: PREGNANCY Bad taste in mouth CYP450 inhibitor |
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How is azithromycin administered and how is its half-life? What are its uses and toxicities?
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Oral, long half-life
Use: Single dose for CHLAMYDIA; COMMUNITY RTIs; also H. flu, Moraxella cat, atypical Mycrobacteria Ototoxicity |
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How is telithromycin administered and how is it better than macrolides? What are its uses? Why is it limited in its uses?
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Oral, binds tightly to ribosomes so less resistant
Use: COMMUNITY RTIs AE: severe HEPATOTOXICITY (limits use), visual, gi |
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What are the lincosamides? How is its absorption and distribution?
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CLINDAMYCIN, lincomycin
Oral, good absorp, wide distrib (abscesses) |
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What is the spectrum of clindamycin and its uses?
What are its toxicities? |
Community staph/strep, anaerobes, NOT gram(-) aerobes
Uses: ANAEROBIC, staph osteomyelitis (bone), topical for acne Tox: GI (pseudomembranous colitis!) Also allergies (rash), hepatotox, neutropenia |
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What are the streptogramins? What are their uses? What toxicities/interactions do they have?
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Quinupristin-dalfopristin (comb) - bacteriCIDAL, IV
Use: MRSA, VRSA, PRSP, VRE AE: pain, arthralgia-myalgia; INHIBIT CYP3A4 |
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What is the MOA of linezolid? What are its kinetics and toxicities?
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Bind 23s portion of 50s subunit, inhibit INITIATION COMPLEX, bacteriostatis
Oral/IV Well tolerated, weak MAO inhibitor (avoid tyramine foods, interaction with pseudoephedrine/phenylpropanolamine/antidepressants - serotonin syndrome) Thrombocytopenia, neutropenia - immunosuppressed pts |
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What is linezolid reserved for?
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Spectrum: drug-resistant GRAM+ cocci
Use: VRE, MRSA, PRSP no cross-res, resistance rare, expensive! |
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What is the MOA of mupirocin and it uses?
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Block RNA and protein synthesis
TOPICAL: staph/strep skin inf, NASAL app: MRSA |
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What is the MOA of rifamixin? What are its uses and when is it CI?
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Binds to RNA polymerase to inhibit RNA synthesis
Use: (broad) tx traveler's diarrhea (NON-invasive E coli), HEPATIC encephalopathy, REFRACTORY C. difficile colitis CI: pregnancy |
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