Chloramphenicol + Hydroxypropylmethylcellulose

Usage

Chloramphenicol + Hydroxypropylmethylcellulose is primarily prescribed for superficial bacterial ocular infections, such as bacterial conjunctivitis. Hydroxypropylmethylcellulose (HPMC) acts as a lubricant and helps chloramphenicol stay in contact with the eye surface.

• Pharmacological Classification: Antibiotic (Chloramphenicol) and Lubricant (Hydroxypropylmethylcellulose)
• Mechanism of Action: Chloramphenicol inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, preventing peptide bond formation. HPMC increases the viscosity of the eye drops, prolonging contact time with the ocular surface.

Alternate Names

While the combination itself may not have distinct alternate names, the individual components do.

• Chloramphenicol: Is also known as Chloromycetin.
• Hydroxypropylmethylcellulose: Is frequently abbreviated as HPMC.

There are many brand names that market the components individually, such as Chlorsig (Chloramphenicol) and many more that combine these two as well.

How It Works

• Pharmacodynamics: Chloramphenicol exerts a bacteriostatic effect by inhibiting protein synthesis, thereby limiting bacterial growth. HPMC lubricates and protects the ocular surface, reducing discomfort and promoting healing.

• Pharmacokinetics:

  • Absorption: Topical ocular administration results in limited systemic absorption of chloramphenicol.
  • Metabolism: Primarily hepatic.
  • Elimination: Renal and hepatic excretion.

• Mode of Action: Chloramphenicol acts by binding reversibly to the bacterial 50S ribosomal subunit, specifically at the peptidyl transferase center. This interaction blocks the formation of peptide bonds, thereby disrupting bacterial protein synthesis. HPMC acts as a demulcent and a viscosity-increasing agent on the ocular surface.

• Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation: Chloramphenicol inhibits the bacterial enzyme peptidyl transferase. HPMC has no known binding affinity for human receptors.

• Elimination Pathways: Chloramphenicol is metabolized in the liver and eliminated primarily through the kidneys and bile.

Dosage

Standard Dosage

Adults: Instill 1-2 drops into the affected eye every 2 hours for the initial 1-2 days. If improvement is noted, the frequency can be reduced to 1 drop 4 times daily for a maximum of 5 days. An ointment can be used at night or as an alternative to drops at a frequency of 3-4 times per day.

Children: Dosage should be determined by a physician considering the child’s age and weight. Children older than two years may follow the adult dosage.

Special Cases:

• Elderly Patients: Use with caution. Adjust dosage based on renal and hepatic function.
• Patients with Renal Impairment: Use cautiously, monitoring renal function.
• Patients with Hepatic Dysfunction: Use with caution. Adjust dosage as needed.
• Patients with Comorbid Conditions: Evaluate for drug interactions.

Clinical Use Cases

Dosing for the combination in clinical settings such as intubation, surgical procedures, mechanical ventilation, and ICU stays is generally the same as the standard adult ophthalmic dosage. However, it is best practice for a clinician to determine the appropriate dosage and usage based on individual patient circumstances. Chloramphenicol is not usually recommended for such systematic applications.

Dosage Adjustments

Dosage modifications may be required depending on patient factors, such as renal or hepatic dysfunction.

Side Effects

Common Side Effects:

Transient burning or stinging upon instillation, blurred vision, eye irritation, and itching.

Rare but Serious Side Effects:

Aplastic anemia (bone marrow failure), optic neuritis (inflammation of the optic nerve).

Long-Term Effects:

Prolonged use of topical chloramphenicol can lead to the development of resistant bacterial strains.

Adverse Drug Reactions (ADR):

Severe hypersensitivity reactions, including angioedema and anaphylaxis.

Contraindications

Hypersensitivity to any component of the formulation. Not suitable for viral or fungal eye infections. Patients with history of blood dyscrasias, especially aplastic anemia, should avoid use.

Drug Interactions

Chloramphenicol interacts with several medications, including those that suppress bone marrow function. It can also interact with some anticoagulants, oral contraceptives, and other antibiotics. Always check for potential drug interactions with any concomitantly prescribed or over-the-counter medications.

Pregnancy and Breastfeeding

Topical ophthalmic use of chloramphenicol is generally considered safe during pregnancy and breastfeeding as the systemic absorption is minimal. However, it is essential to weigh the benefits against potential risks, particularly with oral or IV administration. Monitor infants for potential side effects, like poor feeding and gastrointestinal disturbances. An alternative agent might be preferred.

Drug Profile Summary

• Mechanism of Action: Inhibits bacterial protein synthesis, lubricates the eye.
• Side Effects: Burning/stinging, blurred vision, aplastic anemia (rare).
• Contraindications: Hypersensitivity, history of blood dyscrasias.
• Drug Interactions: Bone marrow suppressants, anticoagulants, others.
• Pregnancy & Breastfeeding: Generally safe topically.
• Dosage: 1-2 drops every 2 hours initially, then less frequently.
• Monitoring Parameters: Complete blood count (CBC) if prolonged use, particularly in infants.

Popular Combinations

Often combined with other ophthalmic antibiotics or corticosteroids. Combination formulations should be used cautiously due to increased risk of side effects.

Precautions

• Screen patients for hypersensitivity, blood disorders, and other contraindications.
• Exercise caution in special populations.
• Limit use to the affected eye(s) and avoid touching the applicator tip to any surface.

FAQs (Frequently Asked Questions)

Q1: What is the recommended dosage for Chloramphenicol + Hydroxypropylmethylcellulose?

A: For adults and children over 2 years, instill 1-2 drops every 2 hours initially, then taper to 4 times daily if there’s improvement, for a maximum of 5 days. A physician should determine the dosage for younger children.

Q2: What are the most common side effects?

A: Transient burning or stinging, blurred vision, eye irritation, itching.

Q3: What are the serious side effects to watch for?

A: Aplastic anemia, optic neuritis. Seek immediate medical attention if these occur.

Q4: Can I use this combination while pregnant or breastfeeding?

A: Topical use is generally considered safe, but consult a physician to assess the individual benefit-risk profile.

Q5: How does chloramphenicol work against bacterial infections?

A: It inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit.

Q6: What is the role of Hydroxypropylmethylcellulose in this combination?

A: It acts as a lubricant, prolonging the contact time of chloramphenicol with the eye and enhancing its effectiveness.

Q7: Are there any specific contraindications for this medication?

A: Yes, contraindications include hypersensitivity to any component, history of blood dyscrasias (especially aplastic anemia), and viral or fungal eye infections.

Q8: What should I advise my patients regarding the use of this eye drop?

A: Advise them about the proper administration technique, potential side effects, and the importance of completing the full course of treatment, even if symptoms improve.

Q9: How should this medication be stored?

A: Eye drops should be stored as per the manufacturer’s instructions. Usually, they can be kept at room temperature after opening, but should be discarded after 4 weeks.