Walters - Misc. Antibiotics Flashcards
What is Chloramphenicol used for?
Used for resistant and serious aerobic/anaerobic G+/G- infections (meningitis)
What is the mechanism for Chloramphenicol?
(same as tetracyclines) inhibits binding of aminoacyl-tRNA to acceptor site
Why is Chloramphenicol problematic in humans?
it also inhibits mammalian mitochondrial peptidyltransferase (Erythropoietic cells are most sensitive), decreases G6PD and inhibits P450
what causes Gray Baby Syndrome in infants?
caused by Chloramphenicol - insufficient glucoronyl transferase to conjugate drug for elimination and underdeveloped renal function
What are the side effects of Chloramphenicol?
fatal blood dyscrasias, depressed respiration, cardiovascular collapse and cyanosis (gray baby)
When is Quinupristin/Dalfopristin used?
given IV for MRSA and vancomycin resistant infections (synergistic medications = cidal)
what is the mechanism for Quinupristin/Dalfopristin?
Quinupristin releases peptidyl-tRNA from donor site of peptidyltransferase, and Dalfopristin inhibits binding of aminoacyl-tRNA to acceptor site and of peptidyl-tRNA to donor site of peptidyltransferase
what do both Quinupristin and Dalfopristin inhibit?
CYP3A = decreases metabolism of warfarin and diazepam
what are the side effects of Quinupristin/Dalfopristin?
Superinfection, venous irritation, arthralgias/myalgias, and hyperbilirubinemia
what is Linezolid used for?
for Enterococcus faecium, MSSA, MRSA and other vancomycin-resistant infections (can be static or cidal)
what is a risk with using Linezolid?
myelosuppression - blood dyscrasias and colitits (weekly complete blood counts recommended)
what is the mechanism for Linezolid?
inhibits formation of the initiation complex on the ribosome
what does Linezolid weakly inhibit and what might it cause?
MAO-A and may cause 5-HT syndrome when used with other Rxs that enhance 5-HT activity (antidepressants)
what can chronic use of Linezolid cause?
reversible optic neuropathy, irreversible peripheral neuropathy, and lactic acidosis (do not use longer than 28 days)
what is Clindamycin used for?
topical for acne or suppository for bacterial vaginosis (has been used with high dose PCN for group A strep)
what are the side effects with Clindamycin?
risk of pseudomembranous colitis (C.diff)
what is the mechanism for Clindamycin?
inhibits translocation from A site to P site on ribosome
what is Polymyxin B used for?
effective against G- organisms = bacterial infections of conjunctiva and lids (only used topical)
what are the side effects of Polymyxin B?
very nephrotoxic and neurotoxic (neuromuscular block)
what is the mechanism for Polymyxin B?
it is a cidal cationic detergent and has a postantibiotic effect
what is Colistimethate?
Polymyxin E - cidal cationic detergent, IV/IM for G- rods (neurotoxic and nephrotoxic)
what is Rifaximin used for?
travelers diarrhea from non-invasive strains of E.coli and decreases risk of hepatic encephalopathy in patients with advanced liver disease by decreasing number of ammonia-producing bacteria
what is the mechanism for Rifaximin?
binds DNA-dependent RNA polymerase
what are the side effects of Rifaximin?
flatulence, abdominal pain and urgency to defecate
what may occur due to the structural similarity of Rifaximin and Rifampin?
may lead to cross-resistance and emergence of rifampin-resistant staph
what two drugs are used to treat IMPETIGO?
Mupirocin and Retapamulin
what is the mechanism of Mupirocin?
inhibits bacterial isoleuyl t-RNA synthetase
what is the mechanism of Retapamulin?
blocks acceptor and donor sites of peptidyl transferase
what is Nitrofurantonin used for?
prevention and treatment of G+/G- UTIs
what is the mechanism for Nitrofurantonin?
concentrates in renal tubules for local effect and is reduced by urinary tract bacteria to reactive intermediate that damage DNA, ribosomes, cell wall, etc. (non-specific mechanism)
what are the acute symptoms of using Nitrofurantonin?
fever, chills, cough, pulmonary infiltrates during 1st week of treatment (reversible)
what are the chronic symptoms (6 months) of using Nitrofurantonin?
malaise, DOE, cough, altered PFTs, pneumonitis, fibrosis
when should you avoid using Nitrofurantonin?
if patient has a history of cholestatic jaundice or hepatic dysfunction with prior use
what is the caution with using Nitrofurantonin?
discolors the urine brown and pulmonary reactions have been reported
when is Daptomycin used?
it is a cidal parenteral lipopeptide for G+ and MRSA skin and systemic infections (NOT for pneumonia)
what is the mechanism for Daptomycin?
forms pores in cytoplasmic membrane - loss of K+ - depolarization and inhibition of DNA, RNA, and protein synthesis
what is a side effect of Daptomycin?
increases creatine kinase (CK) and is excreted by kidneys unchanged
what is Quinidine used for?
IV for life-threatening Plasmodium falciparum (parasite)
what is a side effect of using Quinidine?
can cause arrhythmias - monitor ECG
what is Rifampin used for?
effective against most G+ and many G- organisms - good against staph and MRSA
what is the mechanism for Rifampin?
inhibits DNA-dependent RNA polymerase thus inhibiting RNA synthesis (kills intracellular and extracellular organisms)
how is Rifampin excreted?
mostly through bile - enterohepatic recirculation
what are some side effects of Rifampin?
rash, fever, nausea, vomiting, re-orange color to urine, feces, saliva, sweat, tears, jaundice, and hepatitis
how is Rifampin an enzyme reducer?
it decreases activity of digoxin, anticoagulants, quinidine, and oral contraceptives
