Micro 15 - Protein Synthesis Inhibitors

Question 1

What is the mechanism of action of Linezolid?

Answer 1

Binds to 23S RNA and interacts with the bacterial initiation complex.

Question 2

In what clinical cases do we use Linezolid?

Answer 2

MRSA (Methicillin Resistant Staph Aureus) and VRE (Vancomycin Resistant Enterococci). Used orally (outpatient).

Question 3

What is the mechanism of action of Tetracycline?

Answer 3

Binds to the 30s and prevents attachment of aminoacyl-tRNA. They are bacteriostatic and limited CNS penetration.

Question 4

What are 4 commonly used tetracyclines?

Answer 4

Tetracycline, doxycycline, demeclocycline, minocycline.

Question 5

How is Doxycycline eliminated?

Answer 5

Fecally, so it can be used in patients with renal failure.

Question 6

What are the clinical uses for tetracyclines?

Answer 6

[VACCUUM THe BedRoom]
Vibro cholerae, Acne, Chlamydia, Ureaplasma urealyticum, Mycoplasma pneumoniae, Tularemia, Helicobacter pylori, Borrelia burgdorferi, Rickettsia.

Question 7

What substances must be avoided when taking tetracyclines?

Answer 7

Milk, antacids, Iron, calcium and magnesium.

Question 8

What are the side effects of tetracyclines?

Answer 8

GI distress, Discoloration of teeth in children, Inhibits bone growth in children, photosensitivity.

Question 9

What are the three medications that can cause photosensitivity?

Answer 9

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Sulfonamides, Amiodarone, Tetracycline.

Question 10

What are 5 commonly used aminoglycosides?

Answer 10

Getamicin, Neomycin, Amikacin, Tobramycin, Streptomycin.

Question 11

What is the mechanism of action of aminoglycosides?

Answer 11

Binds the 30s Ribosome. Bactericidal. Inhibits the formation of the initiation complex and causes misreading of mRNA.

Question 12

What is the weakness of aminoglycosides?

Answer 12

It requires oxygen to work, therefore ineffective against anaerobes.

Question 13

What are the clinical uses of Aminoglycosides?

Answer 13

Severe G(-) rod infections. They work synergistically with beta-lactam antibiotics (ampicillin with gentamicin in neonatal infections). Neomycin is used in Bowel surgery.

Question 14

What are the side effects of aminoglycosides?

Answer 14

Nephrotoxicity (esp when used with cephalosporins). Ototoxicity (esp when used with loop diuretics). Teratogenic.

Question 15

What are 3 commonly used macrolides?

Answer 15

Erythromycin, Azithromycin, Clarithromycin.

Question 16

What is the mechanism of action of macrolides?

Answer 16

Inhibits protein synthesis by blocking translocation. It binds to the 23s rRNA of the 50s ribosomal subunit. Bacteriostatic.

Question 17

What are the clinical uses of macrolides?

Answer 17

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Pneumonia (atypical), URI (strep pneumo, strep pyogenes), STD (chlamydia, gonorrhea). Safe in pregnancy.

Question 18

What are the side effects of Macrolides?

Answer 18

Prolonged QT interval, GI discomfort, Rarely acute cholestatic hepatitis (w/ erythromycin estolate)., rare cases of eosinophilia.

Question 19

What are some drug interaction of macrolides?

Answer 19

Increase serum concentration of theophylline. Oral anticoagulants (e.g. Warfarin).

Question 20

What is the mechanism of resistance against macrolides?

Answer 20

Methylation of the 23 rRNA binding sire.

Question 21

What is the mechanism of action of chloramphenicol?

Answer 21

Inihibits the 50s peptidyltransferase activity. It is bacteriostatic.

Question 22

What are the clinical uses of Chloramphenicol?

Answer 22

Meningitis by H.influenzae, N.meningitidis, S.pneumoniae.

Question 23

What are the side effects of chloramphenicol?

Answer 23

Gray baby syndrome (because premature infants lack liver UDP-glucoronyl transferase, very important in degrading chloramphenicol), anemia (dose dependent), aplastic anemia (dose dependent).

Question 24

What are the symptoms of gray baby syndrome?

Answer 24

Buildup of toxic metabolites of chloramphenicol, vomiting, ashen gray color of the skin, poor muscle tone, cyanosis, CV collapse.

Question 25

What is the treatment for Gray baby syndrome?

Answer 25

Stop chloramphenicol, exchange transfusion, phenobarbital (induces the production of UDP-glucoronyl tranferase).

Question 26

What is the mechanism of action of Clindaymycin?

Answer 26

Blocks peptide bond formation with the 50s ribosomal subunit. Bacteriostatic.

Question 27

What are the clinical uses of Clindamycin?

Answer 27

Anaerobic infections, MRSA infections, Protozoal infections, Topically for treating acne. For bacteriodes fragilis and Clostridium perfringens. Skin abscess that are caused by MRSA can be treated by oral clindamycin.

Question 28

What are the side effects of clindamycin?

Answer 28

Pseudomembranous colitis.

Question 29

What is the mechanism of action of streptogramins (Quinupristin/Dalfopristin (Synercid))?

Answer 29

Act by bind to the 23s portion of the 50s ribosome.

Question 30

What are the clinical uses of streptogramins?

Answer 30

MRSA, VRE, staph and strep skin infections.

Question 31

What are the side effects of streptogramins?

Answer 31

Hepatoxicity, pseudomembranous colitis, altralgias, myalgias. Inhibits cytochrome p450.

Question 32

What causes gray baby syndrome? Gray man syndrome? Red man syndrome?

Answer 32

Gray baby syndrome: Use of chloramphenicol. Gray man syndrome: Use of amiodarone. Red man syndrome: Use of Vancomycin.

Question 33

What medications target the 30s ribosomes? Which ones target 50s ribosomes?

Answer 33

[buy AT 30, CCELL at 50] | 30s: Aminoglycosides, Tetracyclines. 50s: Chloramphenicol, Clindamycin, Erthromycin (macrolides), Lincomycin, Linezolid.