C/11. Chloroamphenicol. Polymyxins. Antifolate Drugs

Question 1

Drugs need to know in this topic

Answer 1

Chloroamphenicol
Colistin
Sulfamethoxazole+trimethoprim
Proguanil

Question 2

Chloroamphenicol

Answer 2

Binds reversibly to the 50S subunit of bacterial ribosome, inhibits peptide bond formation
Bacteriostatic effect

Wide spectrum
Clinically use as systemic drug is limited due to toxicity
Empiric tx of bacterial meningitis

Oral/parenteral
Freely crosses placenta and blood-barin barrier
Hepatic metabolism
Inhibitor of CYP450 enzymes

Resistant bacteria expressing acetyltransferase

GI symptoms
BM suppression
Grey baby syndrome: decreased RBC, cyanosis, cardiovascular collapse in infants

Question 3

Trimethoprim with sulfonamides (TMP-SMX)

Answer 3

Antimetabolite(anti-folate)
A substance inhibiting cell growth by comepting, substituting with/for a natural substrate in an enzymatic process

Each has bacteriostatic effects
Both are bactericidal effect

Gram-negative infections; E.coli, salmonella, shigella, H. Influenza, M catarrhalis
Gram-positive infections; Community-acquired MRSA, staph, strep
Pneumocystis jirovecii

Weak base
Renal excretion

BM suppression
Enterocolitis

Question 4

Proguanil

Answer 4

Malaria prophylaxis w/atovaquone

Oral, prodrug

Generally well tolerated

Question 5

Polymyxin E(colistin)

Answer 5

Acts as cationic detergent
Binds and inactivates endotoxin
Bactericidal effect

Against Gram -
Systemic use is limited due to severe SEs
Limited to topical tx of superficial skin infections

Topical/parenteral administration

Neurotoxicity;dizzness, ataxia
Nephrotoxicity

Question 6

Sulfonamide HSR

Answer 6

Skin rash
Fever
Urticaria
Steven-jhonson syndrome (exfoliative dermatitis)