Usage
- Chloramphenicol + Polymyxin B is prescribed for the treatment of superficial bacterial infections of the eye and/or ear. These infections can involve the conjunctiva, cornea, or external auditory canal.
- Pharmacological Classification: Antibiotic combination.
- Mechanism of Action: This combination exerts a synergistic bactericidal effect. Chloramphenicol inhibits bacterial protein synthesis, while Polymyxin B disrupts the bacterial cell membrane.
Alternate Names
- While no official alternate generic names exist, regional variations may occur.
- Brand Names: Numerous brand names exist depending on the manufacturer and region. Examples based on the sources include Ocupol, Ocupol DX.
How It Works
- Pharmacodynamics: Chloramphenicol acts as a bacteriostatic agent by binding to the 50S ribosomal subunit, inhibiting protein synthesis. Polymyxin B acts as a bactericidal agent by binding to the cell membrane of gram-negative bacteria, increasing permeability and leading to cell death.
- Pharmacokinetics:
- Absorption: Both drugs are minimally absorbed systemically after topical ocular or otic administration.
- Metabolism: Chloramphenicol is primarily metabolized in the liver. Polymyxin B is not extensively metabolized.
- Elimination: Chloramphenicol metabolites are excreted in the urine. Polymyxin B is excreted primarily unchanged in the urine, though elimination may be reduced in patients with renal impairment. The elimination of both drugs might be influenced by hepatic and renal functions.
- Mode of Action: Chloramphenicol inhibits peptidyl transferase activity at the bacterial ribosome. Polymyxin B disrupts the integrity of the bacterial cell membrane by interacting with phospholipids. No specific receptor binding, enzyme inhibition (other than the mentioned peptidyl transferase inhibition), or neurotransmitter modulation are primarily involved.
Dosage
Standard Dosage
Adults:
- Ophthalmic: 1-2 drops every 3-4 hours for 7-10 days or as prescribed by a physician. Ointment: A small amount (approximately half an inch ribbon) applied to the affected eye(s) at bedtime or as directed.
Children:
- Ophthalmic: Similar to adult dosing for eye infections. Pediatric safety and efficacy have not been fully established, especially in neonates and young infants. Use with caution under close medical supervision.
Special Cases:
- Elderly Patients: No specific dosage adjustments are typically needed for elderly patients, but monitor for any signs of toxicity.
- Patients with Renal Impairment: For ophthalmic use, monitor closely for nephrotoxicity. For systemic administration of polymyxin B (not the combined formulation, since it’s mostly topical), dose adjustment is necessary.
- Patients with Hepatic Dysfunction: Monitor patients with hepatic impairment closely, as chloramphenicol is metabolized by the liver. Dose adjustments may be necessary for systemic forms but are less critical in ophthalmic use.
- Patients with Comorbid Conditions: Careful monitoring is advised in patients with pre-existing blood dyscrasias or bone marrow suppression, as chloramphenicol has been associated with blood-related adverse effects.
Clinical Use Cases
The provided sources primarily focus on standard eye/ear infections. The combination isn’t typically used in clinical settings like intubation, surgical procedures, mechanical ventilation, ICU, or emergency situations. In these situations, systemic antibiotics are generally preferred and chosen based on the specific infectious agent and the patient’s overall condition.
Dosage Adjustments
Dose modifications are generally not required for topical ophthalmic or otic use of Chloramphenicol + Polymyxin B, except in cases of severe renal impairment, where polymyxin B dose adjustments (for systemic administration) need to be considered.
Side Effects
Common Side Effects
- Burning or stinging sensation in the eyes or ears
- Temporary blurred vision
- Itching, redness, or irritation at the application site
- Eyelid swelling or crusting
Rare but Serious Side Effects
- Bone marrow suppression (related to chloramphenicol systemic absorption, though rare with topical application)
- Optic neuritis
- Allergic reactions (e.g., skin rash, itching, swelling)
Long-Term Effects
- Overgrowth of non-susceptible organisms, including fungi, with prolonged use.
Adverse Drug Reactions (ADR)
- Gray baby syndrome (in neonates with systemic chloramphenicol exposure, though rare with topical application)
- Aplastic anemia (rare, but serious)
Contraindications
- Hypersensitivity to chloramphenicol or polymyxin B
- Viral infections of the eye (e.g., herpes simplex keratitis, vaccinia, varicella)
- Fungal or mycobacterial infections of the eye or ear
- Damaged cornea or ulceration
Drug Interactions
- Chloramphenicol can interact with drugs that also suppress bone marrow.
- No clinically significant drug interactions are specifically reported for polymyxin B ophthalmic formulations. However, systemic Polymyxin B can interact with nephrotoxic or neurotoxic drugs.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: The FDA doesn’t have an assigned pregnancy category, but this drug is considered unsafe during pregnancy.
- Both chloramphenicol and polymyxin B can cross the placenta and potentially cause harm to the developing fetus.
- The drugs can be excreted in breast milk and pose risks to nursing infants. The combination is contraindicated.
Drug Profile Summary
- Mechanism of Action: Chloramphenicol: Protein synthesis inhibitor; Polymyxin B: Cell membrane disruptor.
- Side Effects: Burning, stinging, blurred vision, irritation, itching, redness. Rare but serious: Bone marrow suppression.
- Contraindications: Hypersensitivity, viral eye infections, fungal/mycobacterial infections.
- Drug Interactions: Drugs causing bone marrow suppression for Chloramphenicol.
- Pregnancy & Breastfeeding: Contraindicated.
- Dosage: Varies by age and formulation (drops vs. ointment). See detailed section above.
- Monitoring Parameters: Observe for signs of infection resolution, allergic reactions, and any signs of bone marrow suppression if systemic absorption is suspected.
Popular Combinations
This medication itself is a combination product. Adding other topical ophthalmic agents without clear clinical justification is generally discouraged.
Precautions
- General Precautions: Assess for hypersensitivity before initiating therapy. Monitor renal function, especially with prolonged use or if the patient has pre-existing renal disease.
- Specific Populations:
- Pregnant Women: Contraindicated.
- Breastfeeding Mothers: Contraindicated.
- Children & Elderly: Use with caution.
- Menstruating Individuals: No specific precautions mentioned.
- Lifestyle Considerations: Avoid contact lenses during treatment. Temporary blurred vision may affect driving or operating machinery.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Chloramphenicol + Polymyxin B?
A: The ophthalmic dosage varies depending on the severity of the infection. Typically, 1-2 drops every 3-4 hours for 7-10 days. Ointment can be applied at bedtime.
Q2: What are the common side effects?
A: Common side effects include temporary burning, stinging, blurred vision, irritation, itching, and redness.
Q3: Can this medication be used during pregnancy or breastfeeding?
A: No, Chloramphenicol + Polymyxin B is contraindicated during pregnancy and breastfeeding.
Q4: How does Chloramphenicol + Polymyxin B work?
A: Chloramphenicol inhibits bacterial protein synthesis, while Polymyxin B disrupts the bacterial cell membrane.
Q5: What should I do if I miss a dose?
A: Apply the missed dose as soon as you remember, unless it’s almost time for your next dose. Do not double the dose.
Q6: Are there any drug interactions I should be aware of?
A: Inform your doctor about all other medications you are taking, especially those that also suppress bone marrow function.
A: Contact lenses should be avoided during treatment with Chloramphenicol + Polymyxin B.
Q8: What are the signs of a serious allergic reaction?
A: Seek immediate medical attention if you experience symptoms like skin rash, itching, swelling of the face, lips, or tongue, or difficulty breathing.
Q9: How long does treatment typically last?
A: Treatment typically lasts for 7-10 days but can vary depending on the infection’s severity.
Q10: Can Chloramphenicol + Polymyxin B treat viral or fungal eye infections?
A: No, this medication is effective only against bacterial infections. It is not effective against viral or fungal eye infections.
