Walters - Misc. Antibiotics

Question 1

What is Chloramphenicol used for?

Answer 1

Used for resistant and serious aerobic/anaerobic G+/G- infections (meningitis)

Question 2

What is the mechanism for Chloramphenicol?

Answer 2

(same as tetracyclines) inhibits binding of aminoacyl-tRNA to acceptor site

Question 3

Why is Chloramphenicol problematic in humans?

Answer 3

it also inhibits mammalian mitochondrial peptidyltransferase (Erythropoietic cells are most sensitive), decreases G6PD and inhibits P450

Question 4

what causes Gray Baby Syndrome in infants?

Answer 4

caused by Chloramphenicol - insufficient glucoronyl transferase to conjugate drug for elimination and underdeveloped renal function

Question 5

What are the side effects of Chloramphenicol?

Answer 5

fatal blood dyscrasias, depressed respiration, cardiovascular collapse and cyanosis (gray baby)

Question 6

When is Quinupristin/Dalfopristin used?

Answer 6

given IV for MRSA and vancomycin resistant infections (synergistic medications = cidal)

Question 7

what is the mechanism for Quinupristin/Dalfopristin?

Answer 7

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

Question 8

what do both Quinupristin and Dalfopristin inhibit?

Answer 8

CYP3A = decreases metabolism of warfarin and diazepam

Question 9

what are the side effects of Quinupristin/Dalfopristin?

Answer 9

Superinfection, venous irritation, arthralgias/myalgias, and hyperbilirubinemia

Question 10

what is Linezolid used for?

Answer 10

for Enterococcus faecium, MSSA, MRSA and other vancomycin-resistant infections (can be static or cidal)

Question 11

what is a risk with using Linezolid?

Answer 11

myelosuppression - blood dyscrasias and colitits (weekly complete blood counts recommended)

Question 12

what is the mechanism for Linezolid?

Answer 12

inhibits formation of the initiation complex on the ribosome

Question 13

what does Linezolid weakly inhibit and what might it cause?

Answer 13

MAO-A and may cause 5-HT syndrome when used with other Rxs that enhance 5-HT activity (antidepressants)

Question 14

what can chronic use of Linezolid cause?

Answer 14

reversible optic neuropathy, irreversible peripheral neuropathy, and lactic acidosis (do not use longer than 28 days)

Question 15

what is Clindamycin used for?

Answer 15

topical for acne or suppository for bacterial vaginosis (has been used with high dose PCN for group A strep)

Question 16

what are the side effects with Clindamycin?

Answer 16

risk of pseudomembranous colitis (C.diff)

Question 17

what is the mechanism for Clindamycin?

Answer 17

inhibits translocation from A site to P site on ribosome

Question 18

what is Polymyxin B used for?

Answer 18

effective against G- organisms = bacterial infections of conjunctiva and lids (only used topical)

Question 19

what are the side effects of Polymyxin B?

Answer 19

very nephrotoxic and neurotoxic (neuromuscular block)

Question 20

what is the mechanism for Polymyxin B?

Answer 20

it is a cidal cationic detergent and has a postantibiotic effect

Question 21

what is Colistimethate?

Answer 21

Polymyxin E - cidal cationic detergent, IV/IM for G- rods (neurotoxic and nephrotoxic)

Question 22

what is Rifaximin used for?

Answer 22

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

Question 23

what is the mechanism for Rifaximin?

Answer 23

binds DNA-dependent RNA polymerase

Question 24

what are the side effects of Rifaximin?

Answer 24

flatulence, abdominal pain and urgency to defecate

Question 25

what may occur due to the structural similarity of Rifaximin and Rifampin?

Answer 25

may lead to cross-resistance and emergence of rifampin-resistant staph

Question 26

what two drugs are used to treat IMPETIGO?

Answer 26

Mupirocin and Retapamulin

Question 27

what is the mechanism of Mupirocin?

Answer 27

inhibits bacterial isoleuyl t-RNA synthetase

Question 28

what is the mechanism of Retapamulin?

Answer 28

blocks acceptor and donor sites of peptidyl transferase

Question 29

what is Nitrofurantonin used for?

Answer 29

prevention and treatment of G+/G- UTIs

Question 30

what is the mechanism for Nitrofurantonin?

Answer 30

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)

Question 31

what are the acute symptoms of using Nitrofurantonin?

Answer 31

fever, chills, cough, pulmonary infiltrates during 1st week of treatment (reversible)

Question 32

what are the chronic symptoms (6 months) of using Nitrofurantonin?

Answer 32

malaise, DOE, cough, altered PFTs, pneumonitis, fibrosis

Question 33

when should you avoid using Nitrofurantonin?

Answer 33

if patient has a history of cholestatic jaundice or hepatic dysfunction with prior use

Question 34

what is the caution with using Nitrofurantonin?

Answer 34

discolors the urine brown and pulmonary reactions have been reported

Question 35

when is Daptomycin used?

Answer 35

it is a cidal parenteral lipopeptide for G+ and MRSA skin and systemic infections (NOT for pneumonia)

Question 36

what is the mechanism for Daptomycin?

Answer 36

forms pores in cytoplasmic membrane - loss of K+ - depolarization and inhibition of DNA, RNA, and protein synthesis

Question 37

what is a side effect of Daptomycin?

Answer 37

increases creatine kinase (CK) and is excreted by kidneys unchanged

Question 38

what is Quinidine used for?

Answer 38

IV for life-threatening Plasmodium falciparum (parasite)

Question 39

what is a side effect of using Quinidine?

Answer 39

can cause arrhythmias - monitor ECG

Question 40

what is Rifampin used for?

Answer 40

effective against most G+ and many G- organisms - good against staph and MRSA

Question 41

what is the mechanism for Rifampin?

Answer 41

inhibits DNA-dependent RNA polymerase thus inhibiting RNA synthesis (kills intracellular and extracellular organisms)

Question 42

how is Rifampin excreted?

Answer 42

mostly through bile - enterohepatic recirculation

Question 43

what are some side effects of Rifampin?

Answer 43

rash, fever, nausea, vomiting, re-orange color to urine, feces, saliva, sweat, tears, jaundice, and hepatitis

Question 44

how is Rifampin an enzyme reducer?

Answer 44

it decreases activity of digoxin, anticoagulants, quinidine, and oral contraceptives