Antibiotic (amphenicol)
Chloramphenicol is a broad-spectrum antibiotic reserved for serious infections in which other, less dangerous antibiotics are ineffective or contraindicated. It can cause serious bone marrow adverse effects, so its use is limited and supervised.
Also known as: Cloranfenicol, Cloromicetina
Phenytoin + chloramphenicol: chloramphenicol inhibits phenytoin metabolism, increasing its serum levels (QUADRO 2).
Chloramphenicol inhibits hepatic microsomal enzymes (including CYP2C9) and can markedly increase phenytoin concentrations; conversely, phenytoin can induce chloramphenicol metabolism, reducing its antibiotic efficacy. QUADRO 2 of Annex 7 records this interaction in the chloramphenicol and phenytoin sections. Phenytoin toxicity (nystagmus, ataxia, drowsiness) is the most feared consequence, especially in patients on near-maximum doses or with hypoalbuminaemia. Monitor phenytoin levels and clinical signs; adjust the phenytoin dose when starting or stopping chloramphenicol and consider an alternative antibiotic when possible.
Chloramphenicol + phenytoin: chloramphenicol inhibits phenytoin metabolism — toxicity risk; monitor levels and neurological signs.
Chloramphenicol inhibits hepatic drug-metabolising enzymes — decreased phenytoin metabolism and increased serum level (QUADRO 2, Chloramphenicol/Phenytoin: "Phenytoin: decreased metabolism").
Watch for signs of phenytoin toxicity (nystagmus, ataxia, diplopia).
Phenytoin toxicity during chloramphenicol.
Monitor phenytoin levels during chloramphenicol (use restricted to serious infections).
Prontuário Terapêutico do INFARMED (11th ed., 2012) — Annex 7, QUADRO 2 (Chloramphenicol; Phenytoin)
Chloramphenicol has no clinically significant food interactions documented; it may be given with or without food.
May be taken with or without food; if nausea occurs, take with food.
DailyMed/FDA (NIH/NLM) — approved Chloramphenicol tablet label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2897e83b-6282-4e0c-bd8e-f389871259b2
FDA label: avoid concomitant therapy with other drugs that may cause bone marrow depression; chloramphenicol causes bone marrow depression (idiosyncratic aplastic anaemia and dose-dependent myelosuppression).
Avoid combination with other myelosuppressants and monitor blood counts during treatment.
DailyMed/FDA (NIH/NLM) — Chloramphenicol, Drug Interactions/WARNINGS: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=aed29594-211d-49ef-813f-131975a8d0e3
FDA label (Pediatric Use): caution in therapy of premature and full-term neonates and infants to avoid Gray syndrome (abdominal distension, cyanosis, vascular collapse) — due to immature metabolic processes, excessive blood levels may result; adjust the dose or monitor concentrations.
Caution in neonates and premature infants; adjust the dose and monitor blood concentrations.
DailyMed/FDA (NIH/NLM) — Chloramphenicol, Pediatric Use: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=aed29594-211d-49ef-813f-131975a8d0e3
Avoid in severe renal impairment; use only if no alternatives exist (dose-dependent depression of haematopoiesis).
Avoid in severe renal impairment; if unavoidable, monitor blood counts.
Prontuário Terapêutico do INFARMED (11th ed., 2012) — Annex 4, Drugs and renal impairment: Avoid in severe renal impairment; use only if no alternatives exist (dose-dependent depression of haematopoiesis).
FDA label (Pregnancy, Category C): no animal reproduction studies and no adequate studies in pregnant women; crosses the placental barrier — use only if the potential benefit justifies the risk (potential fetal toxic effects, including Gray syndrome).
Category C: use only if benefit justifies risk (crosses the placenta).
Excreted in human milk after oral administration — risk of serious adverse reactions in the infant (Gray syndrome); decide between discontinuing nursing or the drug (Nursing Mothers).
Not applicable (no specific contraception requirements in the label).
DailyMed/FDA (NIH/NLM) — approved Chloramphenicol label, Pregnancy/Nursing Mothers section: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=aed29594-211d-49ef-813f-131975a8d0e3
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Broad-spectrum bacteriostatic antibiotic: inhibition of bacterial protein synthesis by binding to the 50S ribosomal subunit. Use restricted to serious infections (FDA label).
Inhibition of peptidyltransferase (50S subunit) — blocks bacterial protein synthesis.
IV form (sodium succinate) for hospital use; also available orally (palmitate preparations). The label notes it crosses the placental barrier after oral administration.
The label does not detail metabolism; the drug is metabolised in the liver (glucuronic acid conjugation) and eliminated renally.
Half-life not detailed in the label; renal excretion is the main route (metabolite recovery in urine).
