PHENIRAM 0.5%W/V OPHTHALMIC SOLUTION

Indications

• Bacterial meningitis
• Typhoid fever
• Severe infections caused by susceptible organisms
• Intra-abdominal infections
• Respiratory tract infections

Dosage

Children: Refer to the BNF for Children for appropriate dosing.

Adults: Refer to specific prescribing guidelines or the BNF for appropriate dosing.

Mechanism of action

Chloramphenicol exerts its antibacterial effects by inhibiting bacterial protein synthesis. It binds to the 50S subunit of the bacterial ribosome, preventing peptide bond formation. This action disrupts the production of essential proteins required for bacterial growth and replication.

Pharmacodynamics

Chloramphenicol is bacteriostatic, meaning it inhibits bacterial growth rather than killing bacteria outright. Its broad-spectrum activity allows it to target a wide range of pathogens. The drug's effectiveness is influenced by the susceptibility of the bacteria, with some strains developing resistance through various mechanisms such as the production of chloramphenicol acetyltransferase, which inactivates the drug.

Pharmacokinetics

Chloramphenicol is well-absorbed when administered orally, achieving peak plasma concentrations within 1 to 2 hours. It undergoes extensive hepatic metabolism, primarily by glucuronidation, and has a half-life of approximately 1 to 3 hours in adults. The drug is excreted mainly in urine, both as metabolites and unchanged drug. Its distribution in body tissues is extensive, with significant penetration into the central nervous system, making it effective for central nervous system infections.

Contra-indications

• Hypersensitivity to chloramphenicol or any of its components
• Bone marrow suppression
• Severe liver impairment
• Pregnancy (especially during the third trimester)

Adverse effects

• Aplastic anemia
• Gray baby syndrome (in neonates)
• Gastrointestinal disturbances (nausea, vomiting, diarrhea)
• Allergic reactions (rash, urticaria)
• Peripheral neuropathy

Interactions

• Increased risk of hematological toxicity when used with drugs that also suppress bone marrow function (e.g., sulfonamides, NSAIDs)
• May enhance the effects of anticoagulants (e.g., warfarin)
• Drugs that induce liver enzymes (e.g., rifampicin) may reduce chloramphenicol levels

Precautions

• Monitor for signs of bone marrow suppression
• Use cautiously in patients with liver impairment
• Assess for potential drug interactions
• Avoid in patients who are pregnant or breastfeeding unless absolutely necessary

Pregnancy

Chloramphenicol is generally contraindicated during pregnancy due to potential risks to the fetus, including the development of gray baby syndrome and other adverse effects.

Breast-feeding

Chloramphenicol is excreted in breast milk and may pose a risk to the nursing infant. Caution is advised when administering to breastfeeding mothers.

Storage

Store in a cool, dry place away from direct light. Keep out of reach of children.

Formulations

• Capsules
• Oral suspension
• Injection (IV/IM)
• Topical ointment