Chloramphenicol - How to Remember It

1. The Name Itself: "CHLORAMPHENICOL"

Use the word as a mnemonic for its key toxicity:

Causes Hematologic problems, Liver inactivates it, Oral/IV form, Rickettsial coverage, Aplastic anemia (Most feared), Plasmid resistance, Hepatic glucuronidation, Enters CSF well, Newborn - Gray baby, Inhibits 50S, Chloramphenicol acetyltransferase, Overgrowth warning, Large spectrum

2. Mechanism - "50S = CLEAL"

Drugs that bind the 50S ribosomal subunit (Bacteriostatic group):

Chloramphenicol, Linezolid, Erythromycin (macrolides), Azithromycin, Lincosamides (clindamycin)

Chloramphenicol specifically inhibits peptide bond formation (transpeptidation step) at the 50S subunit.

3. Uses - Mnemonic: "RMBTH" - "Remember My Big Three H's"

Letter	Use
R	Rickettsial infections (typhus, Rocky Mountain Spotted Fever)
M	Meningitis (alternative when penicillin allergy)
B	Bacteroides (anaerobic coverage)
T	Typhoid fever (Salmonella typhi - historically)
H	H. influenzae meningitis (alternative)

4. Toxicity - Mnemonic: "GAP"

G - Gray Baby Syndrome (neonates can't glucuronidate → drug accumulates → cardiovascular collapse) A - Aplastic Anemia (idiosyncratic, dose-independent - most feared!) P - Pancytopenia (dose-dependent bone marrow suppression - reversible)

5. Pharmacokinetics - Mnemonic: "GLIDE"

G - Glucuronidation in the liver (main inactivation) L - Lipid soluble → penetrates CSF, brain, cells I - IV prodrug (succinate form, hydrolyzed in vivo) D - Dose: 50-100 mg/kg/day every 6 hours E - Excreted in urine (~10% as active drug)

6. Resistance - Easy to Remember

Bacteria make "CAT" to destroy it: Chloramphenicol AcetylTransferase (plasmid-encoded enzyme → acetylates the drug → inactivates it)

7. Quick Recall Summary Card

CHLORAMPHENICOL
├── MOA: 50S ribosome → blocks peptide bond
├── SPECTRUM: Broad (G+, G−, anaerobes, rickettsiae)
├── USES: Rickettsiae, Meningitis (PCN allergy), Typhoid
├── TOXICITY: Gray baby | Aplastic anemia | Pancytopenia
├── RESISTANCE: Chloramphenicol acetyltransferase (CAT)
└── PK: Liver glucuronidation, great CSF penetration

Key high-yield exam points (from Katzung's Basic and Clinical Pharmacology & Harrison's):

Chloramphenicol is bacteriostatic for most, but bactericidal for H. influenzae, N. meningitidis, and some Bacteroides
Gray baby syndrome: neonates lack UDP-glucuronosyltransferase - drug accumulates and causes cardiovascular collapse
Aplastic anemia is idiosyncratic (not dose-related) - this is why it's rarely used in the US despite its effectiveness

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