Broad Spectrum

Question 1

Chloraphenicol

Answer 1

Oral, and IV admin

• Distributed widely in the body - CNS and eyes
• bacteriostatic but bactericidal against meningeal pathogens
• metabolized in the liver - conjugated with gluconric acid (becomes inactive), then excreted in the urine

MOA: reversible binds the 50S subunit and inhibits peptide bond formation

TX:

• should not be used for routine tx - NOT DOC FOR ANYTHING
• Typhoid fever, menigitis, eye infections, gram - infections, Riskettsia brucellosis and RMSF

Spectrum

• Broad spectrum
• not effective against entameoba histolytica, or pseudomonas

SE:

• Reversible bone marrow depression and hematopoetic issues
• Fatal aplastic anemia (with prolonged or repeated therapy)
• Allergy
• Grey baby syndrome - inability to conjugate b/c immautre liver - accumulates
• Minor: GI, blurring vision, digital paresthesias, Neurotoxic, bacterial and fungal superinfeaction (with prolonged use)

Drug interactions

• Inhibts hepatic enyzmes:
• –> Inhibit hepatic metabolism of tolbutamide and chloropropamide- hypoglycemia, warfarin and etc.
• hepatic enzyme accelerators inc. the metabolism
• same binding site as erythromycin

Question 2

Tetracycline

Answer 2

Oral
Absorption from the gut is low and chelate with Al, Mg, and Ca
—- (unabsorbed tetracycline in the gut modify the flora –> emergence of resistant isolates)
-distributes in tissues but not CNS or joints, deposited in bone

MOA: bind 30S and prevent access of aminoacyl tRNA- prevents elongation
- bacteriostatic

spectrum

• gram + and gram -
• intestinal amebiasis, plasmodium falciparum, and bacillary dysentery (shigella)
• Resistant to tetra: B. fragilis, proteus, pseudomonas
• –> Resistant mutantsn transport drug out of the cell (plasmid encoded)

SE:

• Alter the flora ( because unabsorbed): softer, odorless, frothy, yellow stools
• –> overgrowth of psuedomonsa, candida, yeast, entercocci, proteus
• bone and teeth discolouration (not used in pregnant women or children <8yo)
• impair hepatic function
• Renal damage (Faconi syndrome)- renal tubular acidosis
• photosensitization

Question 3

Doxycycline

Answer 3

Tetracycline
- less interaction with food
- good tissue penetration
long half life

Question 4

Minocycline

Answer 4

Tetracycline
- High concentration in saliva and tears
- can be used in menigococcal carrier state (DOC is rifampin) 
- long half life 
-

Question 5

Demeclocycline

Answer 5

Blocks ADH receptor function in the CT

used for SIADH

Question 6

Tigecycline

Answer 6

• IV drug, mostly fecal elimination- some kidney
• long half life
• MOA: BINDS 30S rb subunits- bacteriostatic
  A minocycline derivative - to circumvent resistance
• effective against MRSA, MRSE, PRSP, VRE!!