1. Clinical Overview
Chloramphenicol is a broad-spectrum bacteriostatic antibiotic originally derived from *Streptomyces venezuelae*. It is a potent inhibitor of bacterial protein synthesis. Due to its association with serious and potentially fatal hematological toxicities (aplastic anemia, gray baby syndrome), its use in India is now highly restricted and reserved for the treatment of serious, life-threatening infections where safer alternatives are ineffective or contraindicated. It is primarily used in topical ophthalmic and otic formulations; systemic use (oral/IV) is extremely limited.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: Peak plasma concentrations reached in 1-3 hours. IV: Immediate. Clinical improvement usually seen within 48-72 hours. | Approximately 4-8 hours, necessitating multiple daily doses. | Oral: 75-90% (well absorbed). IV: 100%. |
2. Mechanism of Action
Chloramphenicol binds reversibly to the 50S subunit of the bacterial 70S ribosome. It inhibits the peptidyl transferase activity, thereby preventing the transfer of the growing peptide chain to the newly attached aminoacyl-tRNA. This blocks the formation of peptide bonds, halting bacterial protein synthesis.
3. Indications & Uses
- Acute Typhoid Fever (Salmonella Typhi) - only in multidrug-resistant cases
- Bacterial Meningitis (as an alternative in penicillin/cephalosporin allergy, or resistant strains)
- Rickettsial infections (e.g., Scrub typhus) where tetracyclines are contraindicated
- Topical: Bacterial Conjunctivitis, Otitis Externa
4. Dosage & Administration
Adult Dosage: Oral/IV: 50 mg/kg/day in divided doses every 6 hours. For severe infections (e.g., meningitis): up to 100 mg/kg/day. MAXIMUM: 4 g/day. Duration: Typically 7-14 days, depending on infection.
Administration: Oral: Take on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption, but can be taken with food to reduce GI upset. IV: Administer as a slow intravenous infusion over at least 15-30 minutes. NEVER GIVE INTRAMUSCULARLY (poor absorption, risk of abscess).
5. Side Effects
Common side effects may include:
- Nausea
- Vomiting
- Diarrhea
- Headache
- Mild skin rashes
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Warfarin, Acenocoumarol | Chloramphenicol inhibits hepatic metabolism, increasing anticoagulant effect and risk of bleeding. | Major |
| Phenytoin, Phenobarbital | Chloramphenicol increases phenytoin/phenobarbital levels (inhibits metabolism), causing toxicity. Phenobarbital may decrease chloramphenicol levels. | Major |
| Sulfonylureas (Glibenclamide, Glimepiride) | Increased risk of hypoglycemia due to inhibited metabolism. | Major |
| Cyclophosphamide | Enhanced myelosuppression. | Major |
| Vitamin B12, Folic Acid, Iron Supplements | May mask the early hematological signs of chloramphenicol toxicity. | Moderate |
| Rifampicin | Decreases chloramphenicol levels by inducing metabolism. | Moderate |
| Paracetamol (Acetaminophen) | May increase risk of bone marrow suppression; prolongs chloramphenicol half-life. | Moderate |
7. Patient Counselling
- DO complete the full course as prescribed, even if you feel better.
- DO take on an empty stomach for best effect, unless it causes stomach upset.
- DO inform all your doctors and dentists you are taking chloramphenicol.
- DO get regular blood tests (CBC) as advised by your doctor.
- DONT use for colds, flu, or viral infections.
- DONT share this medicine with anyone else.
- DONT take any other medicines (including OTC, herbal) without consulting your doctor.
8. Toxicology & Storage
Overdose: Nausea, vomiting, epigastric distress, diarrhea, metabolic acidosis, hypotension, hypothermia (Gray Baby Syndrome in infants), bone marrow suppression leading to pancytopenia, confusion, peripheral neuropathy.
Storage: Store in a cool, dry place, protected from light. Keep the container tightly closed. Do not store in the bathroom. Keep out of reach of children. Do not use after the expiry date printed on the pack. For capsules/tablets: Store below 30°C.