Antibiotics

Question 1

Oxacillin, nafcillin, dicloxacillin

Answer 1

Pencillinase-resistant penicillins

• Bulky R group blocks access of beta-lactamase to beta-lactam ring
• Toxicity: interstitial nephritis

Question 2

Ticarcellin, piperacillin

Answer 2

Antipseudomonals

• Susceptible to pencillinase (use with beta-lactamase inhibitors)

Question 3

Clavulanic acid, Sulbactam, Tazobactam

Answer 3

Beta-lactamase inhibitors

• “CAST”

Question 4

Cefazolin, cephalexin

Answer 4

1st generation cephalosporins

Toxicity: vit K deficiency, increased nephrotoxicity of aminoglycosides

Question 5

Cefoxitin, cefaclor, cefuroxime

Answer 5

2nd generation cephalosporins

Toxicity: vit K deficiency, increased nephrotoxicity of aminoglycosides

Question 6

Ceftriaxone, cefotaxime, ceftazidime

Answer 6

3rd generation cephalosporins

• Ceftriaxone treats meningitis, gonorrhea
• Ceftazidime treats Pseudomonas

Toxicity: vit K deficiency, increased nephrotoxicity of aminoglycosides

Question 7

Cefepime

Answer 7

4th generation cephalosporins

• Anti-pseudomonal coverage

Toxicity: vit K deficiency, increased nephrotoxicity of aminoglycosides

Question 8

Ceftaroline

Answer 8

5th generation cephalosporins

• MRSA coverage; no psuedomonas coverage

Toxicity: vit K deficiency, increased nephrotoxicity of aminoglycosides

Question 9

Aztreonam

Answer 9

Monobactam resistant to beta-lactamases

Only treats gram-negative rods

Synergistic with aminoglycosides

Question 10

Imipenem, meropenem, ertapenem, doripenem

Answer 10

Carbapenems

• Wide-spectrum (gram pos, gram neg, anaerobes), beta-lactamase-resistant
• Imipenem always administered with cilastatin (inhibits renal hydropeptidase I) to decrease inactivation of drug in renal tubules
• Meropenem has decreased risk of seizures and is stable to dehydropeptidase I
• Toxicity: GI distress, skin rash, seizures

Question 11

Vancomycin

Answer 11

Bactericidal. Binds D-ala D-ala portion of cell wall precursors.

Toxicity: Nephrotoxicity, Ototoxicity, Thrombophlebitis (“NOT” trouble free); Red Man Syndrome (prevented with slow infusion and antihistamines)

Question 12

Protein synthesis inhibitors

Answer 12

“Buy AT 30, **CCEL **at 50”

Aminoglycosides (bactericidal) and Tetracyclines target 30S

Chloramphenicol, Clindamycin, Erythromycin (macrolides), and Linezolid target 50S

Question 13

Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin

Answer 13

Aminoglycosides

• Bactericidal inhibitors of 30S that inhibit formation of initiation complex, cause misreading of mRNA, and block translocation
• Require O₂ for uptake (ineffective vs. anaerobes)
• Treats severe gram-negative rod infections
• Toxicity: Nephrotoxicity (especially when used with cephalosporins), Neuromuscular blockade, Ototoxicity (especially when used with furosemide), Teratogen
• Resistance: inactivation via acetylation, phosphorylation or adenylation

Question 14

Tetracycline, doxycycline, minocycline

Answer 14

Tetracyclines

• Bacteriostatic inhibitors of 30S that prevent attachment of aminoacyl-tRNA
• Treats Borrelia burgdorferi, M pneumoniae, Rickettsia, Chlamydia, Acne; limited CNS penetration
• Doxycyline can be used in renal failure (fecally eliminated)
• Divalent cations inhibit absorption in gut
• Toxicity: photosensitivity, teratogen
• Resistance: decrease uptake or increase efflux via plasmid-encoded transport pumps

Question 15

Azithromycin, clarithromycin, erythromycin

Answer 15

Macrolides

• Bacteriostatic inhibitors of 23S rRNA subunit of 50S that block translocation (“macroslides”)
• Treats atypical pneumonias, chlamydia, and gram-positive cocci
• Toxicity: GI motility issues, Prolonged QT, cholestatic hepatits, rash, eosinophilia, inhbit cytochrome p450
• Resistance: methylation of 23S rRNA-binding site

Question 16

Chloramphenicol

Answer 16

Bacteriostatic inhibitor of peptidyltransferase at 50S subunit

Treats meningitis (H flu, N meningitidis, S pneumonia) and Rickettsia rickettsii

Toxicity: anemia, aplastic anemia, gray baby syndrome (in premies due to lack liver UDP-glucuronyl transferase)

Resistance: plasmid-encoded acetyltransferase inactivates drug

Question 17

Clindamycin

Answer 17

Bacteriostatic inhibitor of translocation at 50S subunit

Treats anaerobic infections above the diaphragm and GAS

Toxicity: C diff

Question 18

Sulfamethoxasole, sulfisoxazole, sulfadiazine

Answer 18

Sulfonamides

• Bacteriostatic inhibitor of dihydropteroate synthase (converts pteridine and para-aminobenzoic acid to dihydropteroic acid, a precursor of folate)
• Toxicity: hemolysis in G6PD deficiency, tubulointerstitial nephritis, photosensitivity, kernicterus in infants, displaces warfarin from albumin

Question 19

Trimethroprim

Answer 19

Bacteriostatic inhibitor of dihydrofolate reductase

Toxicity: megaloblastic anemia, leukopenia, granulocytopenia

Question 20

Fluoroquinolones

Answer 20

Bactericidal inhibitors of DNA gyrase (topoisomerase II) and topoisomerase IV

Toxicity: tendonitis, tendon rupture, myalgias, teratogen

Question 21

Metronidazole

Answer 21

Bactericidal, antiprotozoal activity. Forms free radicals in the bacterial cell wall that damage DNA

Treats Giardia, Entamoeba, Trichomonas, Gardnerella vaginalis, Anaerobes below the diaphragm

Toxicity: disulfiram-like reaction with alcohol; metallic taste

Question 22

Linezolid

Answer 22

Bacteriostatic inhibitor of initiation complex formation by binding to the 23S portion fo the 50S subunit

Treats MRSA and VRE