Antibiotics

Question 1

Penicillin

Answer 1

• Inhibits bacterial cell wall synthesis
• pregnancy category B
• GP+ spirochetes
• B lactamase inhibitor - augmentin
• Penicilinase-resistant PCN -> dicloxacillin, methicilin, oxacillin
  AMox - 250 - 500 mg Daily or BID in acne
  -s/e vaginal candida, GI sx, hypersensitivity
  Preg B

Question 2

Cephalosporin

Answer 2

10% cross-reactivity w/ PCNs
Preg Cat B

1st gen: GP > GN
Cefalexin (Keflex) 500 mg bid in acne , -s/e vaginal
candida, GI sx, hypersensitivity
Cefazolin (Ancef)
Cefadroxil (Duracef)

2nd genGP = GN
Cefaclor (Ceclor)
Cefuroxime (Ceftin)

3rd gen: GP < GN
Ceftriaxone (Rocephin)
Cefixime (Suprax)

4th gen: ESBL GP, GN (little activity against β-lactamase)
Cefipime (Maxipine)
Ceftraline (Teflaro)

5th gen: MRSA
Ceftobiprole (Zevtera)

Question 3

Tetracyclines (TCNs)

Answer 3

• Binds bacterial ribosomal unit (30s) → blocks bacterial protein synthesis
• GP/GN bacteria, Chlamydia, Mycoplasma, rickettsia, spirochetes
  ↓ Absorption with Fe/Ca2+; pregnancy category D

o Doxycycline: excreted in GI tract, can use in renal failure
- acne 50-100 mg treatment
-acne 20-40 mg submicrobial dose (Oracea)
-PregX
- > photosensitivity minocycline

o Tetracycline: #1c/o fixed drug eruption Ci <
9 y/o due to brown discoloration of gingival teeth

o Minocycline: side effect includes blue-black pigmentation of skin/teeth (green-gray discoloration of mid-portion of
teeth), drug-induced LE, autoimmune hepatitis
- Preg D
- s/e SJS, Lupus-like syndrome, dizziness, tinitis

o Demeclocycline: most phototoxic (then doxycycline)

Sarecycline 60-100mg
-wt based dosing, 1st in class narrow spectrum against GP, including C acnes -> rdcd r/o resistance
-»9 years, preg risk unknown

-S/e-> bone growth resorbtion, especially fibula
-esophagitis, sit up 30-60 min after and take with full glass H20
-photosensitivity, >2 mo Incrs r/o BCC 11%

Question 4

Macrolides

Answer 4

• Preg C (clarithromycin),
• Preg B (erythromycin, azithromycin)
• bacterial ribosomal unit (50s) → blocks protein synthesis; –alternative for PCN-allergic patients;
• GP/ GN bacteria, spirochetes, atypical mycobacteria
• Adverse effects: cholestatic hepatitis, cardiac conduction abnormalities
  -Ertyhromycin -> growing resistance to C acnes
• ↑ levels of p450 substrates like cyclosporine, anticonvulsants, warfarin, digoxin, benzos

Question 5

Fluoroquinolones (FQs)

Answer 5

• inhibits bacterial DNA gyrase;
• spectrum: GN bacteria, strep/staph, certain mycobacteria
• Adverse effects: tendon rupture, cartilage damage in joints, ↑ LFTs, nephrotoxicity
• Pregnancy category C
  i* nhibits CYP1A2 so ↑ levels of warfarin, aminophylline,

Question 6

Clindamycin

Answer 6

• class Lincomycin antibiotics
• Binds bacterial ribosomal unit (50s) → blocks protein synthesis
• Spectrum: GP and anaerobic bacteria
• SE: pseudomembranous colitis (oral form);
• pregnancy category B

Question 7

Rifampin

Answer 7

• Inhibits RNA synthesis
• Spectrum: mycobacteria (tuberculosis and leprosy)
• SE: orange-red discoloration of urine/tears, ↓ OCP efficacy;
• pregnancy category C

Question 8

Aminoglycosides

Answer 8

*Streptomycin, gentamycin, tobramicyin, neomycin - admnstrd IV
* Binds bacterial ribosomal unit (30s) → blocks protein synthesis; used mainly in topical form
* Spectrum: aerobic GN bacteria;
* SE (oral): ototoxicity, nephrotoxicity;
* pregnancy category D

Question 9

Sulfonamides

Answer 9

• Bactrim
• interferes with bacterial folic acid synthesis
• Spectrum: GP/GN bacteria, Chlamydia, Nocardia
• SE: hemolytic anemia (especially if G6PD ), TEN, SJS, AGEP,
• Pregnancy category C (D in third trimester)
  -daily or BID in acne

Question 10

Dapsone

Answer 10

• Antibacterial and anti-inflammatory (mainly toward neutrophils by inhibition of myeloperoxidase); sulfone family
• spectrum: mycobacteria (leprosy, TB)
• Treats: leprosy, dermatitis herpetiformis, autoimmune blistering diseases, erythema elevatum diutinum, pyoderma gangrenosum
• SE: hemolytic anemia (esp if G6PD deficient), cholestatic jaundice, methemoglobinemia, agranulocytosis (2-12 weeks after continuous treatment), motor peripheral neuropathy, acute psychosis
• Pregnancy category C
• Check G6PD for oral but not topical

Question 11

Metronidazole (Flagyl)

Answer 11

• Forms toxic metabolites in bacteria, which inhibit nucleic acid synthesis
• Spectrum includes anaerobes and protozoa
• SE: hypersensitivity, glossitis, disulfiram-like reaction (with alcohol)
• Pregnancy category B

Question 12

Linezolid

Answer 12

• Zyvox
• Inhibits protein synthesis in bacteria
• Treats GP resistant bacteria, MRSA
• SE (long term use): bone marrow suppression and thrombocytopenia
• Pregnancy category C