Antibiotics III Flashcards
(43 cards)
Tetracyclines (2)
doxycycline, tigecycline
Aminoglycosides (4)
Gentamicin, Streptomycin, amikacin, neomycin
Macrolides (2)
Erythromycin, azithromycin
2 subunits of bacterial 70S ribosome are:
30s and 50S
Aminoglycosides are lipid/water soluble and are given Orally/IV
Water soluble, given IV
Gentamicin is bactericidal/bacteriostatic against G+/G- organisms?
Bactericidal, G- (and G+ staph); activity is concentration dependent
Why are aminoglycosides not effective against strict anaerobes?
Passive diffusion through outer membrane porins into periplasmic space; active transport across the plasma membrane into the cytosol is O2-dependent. Transport is enhanced by cell wall inhibitors.
Aminoglycosides binds to the 30S/50S ribosomal subunit? What does this cause?
30S: 1) Interference with formation of the initiation complex. 2) Misreading of mRNA, causing incorrect incorporation of amino acids into proteins. 3) Blockade of translocation inducing premature termination of protein synthesis.
T/F: Aminoglycosides have residual activity for several hours after plasma levels fall below MIC.
True: Long post-antibiotic effect
Streptomycin main use
Second line drug for active TB
Amikacin main use
Least susceptible to inactivation; used in hospitals where resistance to gentamicin and tobramycin is common
Neomycin main use
combined in an OTC topical ointment (Neosporin) with polymyxin B and bacitracin
Adverse reactions of Aminoglycosides
Ototoxicity (Irreversible-Elevated trough plasma levels impede egress out of inner ear cells, Tinnitus is a warning symptom), Nephrotoxicity (reversible), Neuromuscular blockade.
T/F: with Aminoglycosides, it is better to give a single high dose?
True: Less trough time
Mechanism of action for Tetracyclines
Active transport system causes drug accumulation in bacterial cells (mammalian cells lack this transport). Binds 30S ribosomal subunit; inhibits binding of tRNAs to the A-site of the mRNA-ribosomal complex-prevents addition of amino acids: Bacteriostatic
Resistance to tetracyclines
Due to increased drug efflux and production of proteins that interfere with drug binding to the 30S subunit. Tigecycline renders resistant to efflux and increases binding
Tetracycline are all orally effective except for ________ and they form chelates with multivalent cations. Which cations?
Tigecycline, Ca2+, Mg2+, Fe2+, Zn2+, AL3+ Should not be administered with dairy products, iron supplements, MG-containing laxatives and antacids, and bismuth subsalicylate
Therapeutic uses of tetracyclines
Broad spectrum agaisnt aerobic and anaerobic G+ and G-. Effective against rickettsial infections. Oral treatment of acne and periodontal disease. Treatment and prophylaxis of malaria.
Tetracyclines adverse reactions
GI irritation, deposition in bones and teeth, renal toxicity, super infection, hepatotoxicity, photosensitivity
MOA of Macrolides
Bacteriostatic, but can be bactericidal. Binds to 50S subunit; inhibits translocation step of protein elongation
Resistance of macrolides
Efflux transporters, plasma-encoded methylation of 50S subunit that decreases binding affinity; induction of erythromycin ribosome methylation (erm) gene confers a multi-drug resistance phenotype referred to as MLSb
How are macrolides administered and erythromycin is eliminated primarily by hepatic ________ (enzyme)
Administered orally, CYP3A4 (interaction exist)
Therapeutic uses of macrolides
Commonly used agents and a substitute for penicillin sensitive patients. Atypical pneumonias (Legionnaire’s disease, mycoplasma, chlamydial) and other resp. infections. Bordetella pertussis, diptheria, chlamydia
Adverse reactions of macrolides
Generally safe. GI irritation, cholestatic hepatitis with erythromycin, prolonged Q-T interval
