CHLORAMPHENICOL
Clinical safety rating: avoid
Positive evidence of fetus risks but benefits may outweigh risks in some cases
Inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, preventing peptide bond formation.
| Metabolism | Primarily hepatic metabolism via glucuronidation (UDP-glucuronosyltransferase) to inactive metabolites; also reduced by bacterial nitroreductases. |
| Excretion | ~90% renal (5-10% unchanged; remainder as inactive glucuronide), ~10% biliary/fecal |
| Half-life | 1.5-4.0 hours in adults; prolonged to 3-7 hours in neonates and up to 24 hours in severe hepatic impairment |
| Protein binding | 50-60%, primarily to albumin |
| Volume of Distribution | 0.6-1.0 L/kg; distributes well into all tissues including CSF |
| Bioavailability | Oral: 75-90%; IV: 100% |
| Onset of Action | Oral: 30-60 min; IV: immediate; topical: varies |
| Duration of Action | 6-8 hours; prolonged in hepatic impairment |
50-100 mg/kg/day IV divided every 6 hours (not to exceed 4 g/day); for susceptible severe infections, 12.5-25 mg/kg IV every 6 hours.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | In severe renal impairment (eGFR <10 mL/min), dose should be reduced by 50% or interval increased to every 12 hours. Consider monitoring serum concentrations. |
| Liver impairment | In liver failure, dose should be reduced to 50% of usual dose with therapeutic drug monitoring. Avoid in Child-Pugh C cirrhosis. |
| Pediatric use | Neonates <1 week: 25 mg/kg/day IV divided every 24 hours; neonates 1-4 weeks: 25 mg/kg/day IV divided every 12 hours; infants >4 weeks: 50 mg/kg/day IV divided every 6 hours; children: 50-75 mg/kg/day IV divided every 6 hours. |
| Geriatric use | Use caution due to age-related decline in renal and hepatic function; start at lower end of dosing range and monitor serum concentrations to avoid toxicity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Potentiates effects of warfarin phenytoin and sulfonylureas by inhibiting their metabolism Associated with serious and fatal blood dyscrasias like aplastic anemia.
| Breastfeeding | Chloramphenicol is excreted into breast milk with M/P ratio approximately 0.5. Infant exposure is low but may cause bone marrow suppression, dose-dependent. Avoid breastfeeding or use with caution due to risk of idiosyncratic aplastic anemia, though risk is very low with short-term use. Discontinue nursing if maternal therapy required. |
| Teratogenic Risk | Chloramphenicol crosses the placenta. First trimester: no significant increase in major malformations reported; second trimester: no specific pattern; third trimester: risk of gray baby syndrome (fetal cardiovascular collapse) if administered near term due to immature hepatic glucuronidation. Avoid in pregnancy unless no alternative. |
■ FDA Black Box Warning
Serious and fatal blood dyscrasias (aplastic anemia, hypoplastic anemia, thrombocytopenia, granulocytopenia) have occurred after both short and prolonged therapy. Chloramphenicol should not be used for trivial infections or when other safer antibiotics are available.
| Common Effects | meningitis |
| Serious Effects |
History of hypersensitivity or toxic reaction to chloramphenicol; trivial infections (e.g., colds, flu); prophylaxis; significant bone marrow depression; infants less than 2 months of age unless recommended by a specialist.
| Precautions | Monitor complete blood counts before and during therapy; avoid repeated courses; use with caution in patients with hepatic impairment, glucose-6-phosphate dehydrogenase deficiency, or porphyria; potential for gray baby syndrome in neonates. |
| Food/Dietary |
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| Fetal Monitoring | Maternal: CBC with differential and platelet count at baseline and twice weekly due to dose-related bone marrow suppression; serum drug levels if available (therapeutic range 10-20 mcg/mL). Fetal: ultrasound for growth and morphology if exposure in first trimester; newborn monitoring for signs of gray baby syndrome (vomiting, hypothermia, gray pallor, cardiovascular collapse) if exposed near term. |
| Fertility Effects | No specific adverse effects on human fertility reported. Animal studies show no impairment of fertility at therapeutic doses. |
| No significant food interactions reported. However, avoid alcohol due to potential disulfiram-like reaction (flushing, headache, nausea) and increased risk of adverse effects. |
| Clinical Pearls | Chloramphenicol is a bacteriostatic antibiotic that inhibits protein synthesis by binding to the 50S ribosomal subunit. Use is reserved for serious infections due to its association with dose-dependent reversible bone marrow suppression and rare but fatal idiopathic aplastic anemia. Monitor CBC weekly during therapy. It penetrates well into the CNS and eye, making it useful for meningitis and intraocular infections. Contraindicated in neonates due to risk of gray baby syndrome (cardiovascular collapse). Avoid concurrent use with other bone marrow suppressants. |
| Patient Advice | Take chloramphenicol exactly as prescribed, at evenly spaced intervals, and complete the full course even if you feel better. · Notify your doctor immediately if you develop unusual bleeding, bruising, paleness, sore throat, or fever, as these may indicate serious blood disorders. · This drug can cause serious side effects including fatal blood dyscrasias; avoid use in children under 2 years unless directed. · Seek medical attention if you experience blurred vision, confusion, or tingling in the hands or feet. · Avoid alcohol consumption during therapy as it may increase the risk of side effects. · Do not use for trivial infections or save for later use; chloramphenicol is reserved for serious bacterial infections. |