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47 Cards in this Set
- Front
- Back
What class of drugs often produces antibiotic associated colitis (pseudomem. colitis by toxins from C. difficile) ?
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Tetracycline
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What is the MOA of Tetracyclines?
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Inhibit bacterial protein synthesis by binding to 30S ribosomal RNA and blocking amino acyl-charged tRNA binding to the acceptor site on the mRNA-ribosome complex.
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How do organism gain resistance against Tetracycline?
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Naturally occuring R-factor confers an inability of the organism to accumulate drug. Efflux is mediated by a Mg2+ dependent pump mediated by protein Tet A.
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What is the function of protein Tet A?
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Mediates Mg2+ dependent pump that allows efflux of tetracycline from bacterial cell. Confers RESISTANCE.
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What impairs absorption of Tetracycline in the GI?
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divelent and trivalent cations, especially Ca2+, Mg2+, and Al3+
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What tetracycline is useful in eradicating MENINGOCOCCAL CARRIER-STATES due to its ability to enter the meninges in the absence of inflamation and reaches high levels in tears and saliva?
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Minocycline
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What tetracycline is the DOC for extra-renal infections in pts with renal insufficiency due to it's unique elimination through NON-RENAL mechanisms?
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Doxycycline
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What is the main use of Demeclocycline?
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Inhibits action of ADH in the renal tubule, and has been used in the inappropriate secretion of ADH in the renal tubule.
Main application is NOT antibiotic use, it's SIADH! |
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What class of drugs binds to Ca2+ deposited in the newly formed teeth and bone of young children?
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Tetracyclines
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What drug is effective againts tetracycline resistant organisms, MRSE, MRSA, PRSP (pen. resist. strep. pneum) , and VRE (Vanc. Resistant Enterococic) ?
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Tigecycline (Tygacil)
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What is the MOA for Macrolides (Erythro-,Clarithro-,Azithro- mycin) ?
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Inhibition of protein synthesis via binding reversibly to the 50s ribosomal subunits. Aminoacyl translocation reaction is blocked.
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Erythromycin has increased activity at what pH and in what type of organisms?
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Alkaline pH and Gram (+),
Not effective against aerobic enteric gram-negative bacilli |
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What drugs have enhanced activity against Mycobacterium avium intracellulare and some protozoa?
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Clarithromycin and azithromycin
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How does G(+) and G(-) resistance against Macrolides differ?
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G(-) rods produce esterases for hydrolysis
G(+) organisms modify ribosomal binding site of the drug by methylase enzyme that is macrolide inducible or constitutive. |
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What is the MOA for Macrolides (Erythro-,Clarithro-,Azithro- mycin) ?
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Inhibition of protein synthesis via binding reversibly to the 50s ribosomal subunits. Aminoacyl translocation reaction is blocked.
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Erythromycin has increased activity at what pH and in what type of organisms?
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Alkaline pH and Gram (+),
Not effective against aerobic enteric gram-negative bacilli |
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What drugs have enhanced activity against Mycobacterium avium intracellulare and some protozoa?
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Clarithromycin and azithromycin
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How does G(+) and G(-) resistance against Macrolides differ?
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G(-) rods produce esterases for hydrolysis
G(+) organisms modify ribosomal binding site of the drug by methylase enzyme that is macrolide inducible or constitutive. |
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What are the unique pharmacokinetic properties of Azithromycin?
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Extensive tissue distribution, and high drug concentrations within cells. This results in great tissue and secretion drug concentrations including phagocytes.
Also, Does not cause drug interaction with drugs metabolized by p450 enzyme of liver |
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Clarithromycin and Azithromycin have enhanced activity against what organisms?
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Mycobacterium avium intracellulare (atypical mycobacteria) and protozoa
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Erythromycin is metabolized to what compound?
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Metabolised to 14-hydroxy metabolite by hydroxylation.
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What is the main mechanism of elimination of Erythromycin?
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HEPATIC! - in bile
note: Clarithromycin is excreted by renal AND nonrenal mechanisms. |
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What is the elimination half life of Azithromycin?
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68 hours because of extension tissue sequestration and binding
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Hepatitis and Cholestatic Jaundice are rare side effects of what class of drugs?
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Macrolides (-thromycins)
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What is the use of Telithromycin (Ketolide)
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Used in upper respiratory tract infections and its spectrum of activity is good against respiratory pathogens including erythromycin and penicillin resistant pneumococci. (acute sinusitis)
Also, useful against intracellular and atypical bacteria |
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What is the advantage of Telithromycin dosing?
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ONCE daily dose is as effective as clarithromycin, trovafloxacin, and high dose amoxicillin for some infections.
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Aminoglycosides are primarily used to treat infections caused by what type of organism?
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Aerobic gram (--) bacterial.
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Which protein synthesis inhibitor is bacteriCIDAL?
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Aminoglycosides
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What is the MOA of Aminoglycosides?
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Aminoglycosides diffuse through aqueous channels formed by porin proteins of G(-) bact.
Energy-dependent Phase I - transport across cytoplasmic membrane dependent on electron transport After transport across the membrane, they bind to polysomes and interfere with protein synthesis: 1. Block formation of translation initiation-complex 2. misread the mRNA code 3. disrupt polysomes resulting in nonfunctional monosomes. Energy-dependent phase II-abarrant proteins made are inserted into the cell membrane and cause increased aminoglycoside transport. |
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What can interfere with phase I of Aminoglycosides MOA?
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Can be blocked by divalent cations, hyperosmolarity (acidic urine), a reduction in pH, and anaerobic conditions (penetration of the drug is oxygen dependent active transport - i.e - ABCESS)
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What aminoglycoside has a limited spectrum and should not be used against Serratia and pseusomonas aeruginosa?
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Kanamycin
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What organisms are HIGHLY resistant to aminoglycosides?
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Streptococcus pneum and strep pyogenes.
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T/F: Aminoglycosides are absorbed well from the GI and thus, can be given orally.
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FALSE.
NOT absorbed from the GI and less that 1% of the dose is absorbed following oral or rectal administration note: should be given PARENTERALLY. |
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What are the side effects of aminoglycosides?
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- Vestibular and auditory damage
- Tubular necrosis - Neuromuscular blockade |
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What drugs potentiate the adverse effects of aminoglycosides?
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loop diuretics (ethacynic acids and furosemide)
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Gentamycin and Tobramycb are active against most strains of what organism?
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Staph Aureus and Epidermidis
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What is the use of Spectinomycin?
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Spectinomycin is used as an alternative tx for gonorrhea in patient allergic to penicillin or when gonococci are resistant to other agents.
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What is the name of an aminocyclitol antibiotic?
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Spectinomycin
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What is the clinical use of Streptomycin?
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TB, Plague, Brucellosis, TULAREMIA, Infective endocarditis
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What is the clinical use of Gentamycin, Amikacin, Tobramycin, Netilimicin?
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Aerobic G(-) infections (E.coli, Enterobacte, Klebsiella, Proteus, Pseudomonas, and Serratia)
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What 3 drugs are used in Neosporin topical antibiotic and which is for G(+) ?
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Neomycin - (--)
Bacitracin - (+) Polymixin B - (--) |
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What is the clinical use of Chloramphenicol?
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Back up drug for severe salmonella infection (GI) and in pneumococcal and meningococcal meningitis in beta-lactam sensitive persons.
Crosses BBB and is in high concetrations in brain tissue! Also used in rickettsial diseases |
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What drug causes Gray Baby Syndrome?
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Chloramphenicol - due to lack of hepatic glucoronosyl transferase enzyme req. for elimination of the drug.
Other toxic effects: bone marrow disturbance (inhibition of RBC maturation), GI disturbance. |
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Chloramphenicol is effective against what type of organism?
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BROAD SPECTRUM - anaerobic/aerobic - G(+), G(--)
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Clindamycin is effective against what type of organisms?
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Anaerobes, and G(+) Aerobes.
NOT G(-) AErobes. |
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What is the main clinical use for Clindamycin?
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Tx of severe infections due to anaerobes such as Bacteroides.
Also used as alternative to Amoxicillin for prophylaxis of endocarditis before dental surgery in patients with vavlular disease who are penicillin allergic. Drug also has good activity against P. carinii and T. gondii |
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What are the adverse effects if Clindamycin?
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Superinfections such as C.difficile pseudomembranous colitis (won't get from dental prophy use cause it's only 1 dose), GI irritation, rash, neutropenia, hepatic dysfunction.
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